Computer Monitor Repair

Updated 281298



QUESTION NO. P1022-1: I have this HP D2818A. All the voltages are OK, the picture is present but very dark. Brightnes and contrast controls are working, but picture still way too dark. The CRT is a Samsung unit.

A dark/dim Samsung CRT is usually a bad CRT, especially if the voltages are good. Common problem, and they do not restore. If you have not done so already, you might just cross your fingers and check the filaments for correct voltage or ripple, in case the filament supply filter cap has gone bad, or the G2-to-ground cap.




QUESTION NO. P1027-3: I have a NEC monitor (JC1734VMA), when I power it on I get no video. However, if I turn on the monitor before the PC is connected then connect, I have video. I also noticed if the PC is connected and I toggle the monitor on\off\on just righ, it will fire up.

Check out IC801 = UPD78014YCW-Y22 (or -Y24), see if heat or freezespray on IC801 affects the situation. If bad, not good news. the preprogrammed IC801 IC's are expensive; NEI (888-634-7278) wants $$ for these IC's.




QUESTION NO. P1027-5: I am working on several Sony 15" CPD-15F13 Vivitron Monitors all with similar problems. Monitor works fine except a red tinted screen. There are no pots to adjust on these monitors for any RGB balance adjustment. I suspect the CRT's have emission unbalance between guns to cause this problem.

You need a special jig from Sony that hooks up to a computer. But all is not lost, you can TRY readjusting the screen voltage which will change the auto tracking on the crt.

The color balance on these units is done using proprietary Sony digital alignment software too expensive to get for one job, send these out to a shop that already made the investment.




QUESTION NO. P1028-6: Repairing a Dell P1728U found a bad scr but the number will not cross to ecg. The location is Q524 and the number on the part is J307.

The J307 is a 2SJ307 and are available from DALBINI 800-325-2264.

J307 is 2SJ307, a 250-Volt, P-channel MOSFET, not an SCR. You can get one from MCM (800-543-4330) or B & D Enterprises (800-458-6053).




QUESTION NO. P1022-10: I have Highscreen SV 28/3 monitor. If I change resolution, display moves and change dimentions very much. Manual controls of size and position are OK.

The monitor can not handle the refresh rate in that screen size. Lower the refresh rate or change your monitor driver.




QUESTION NO. P1026-1: I have a Samtron 14" monitor model sc-428vs FCC csysc-428vsp. The problem is no video or raster on the top half of the screen. I have checked all components in the vertical section and changed the vertical ic. I am looking for the pin layout for the vertical ic TDA8351 or any help on this problem.

Here is the pinout for a TDA8351: Pin Symbol Description: 1 I drive (+) Input power stage (positive), 2 I drive (-) Input power stage, (negative), 3 Vp Operating supply voltage, 4 Vo(b) Output voltage B, 5 GND Ground, 6 Vfb Input flyback supply voltage, 7 Vo(a) Output volatage A, 8 Vo(guard) Guard output voltage, 9 Vi(fb) input feedback voltage



Idrive+ 1<| '' |


Idrive- 2<| |


Vp 3<| |


Vo(b) 4<| |


GND 5<| |


Vfb 6<| |


Vo(a) 7<| |


Vo(guard) 8<| |


Vi(fb) 9<| |




Pinout of TDA8351 is 1) Input power stage(+), includes Ii(sb) signal bias; 2)Input power stage(-), incl. Ii(sb)signal bias; 3) Vcc; 4)Output Voltage B, 5) GND, 6) Input flyback supply voltage; 7) Output Voltage A; 8) Guard output voltage; 9) Input feedback voltage. NOTE Metal back of IC connected to pin 5. The guard circuit blanks the display during flyback, if there is a short-circuit of the yoke or short-circuit of the output pins (pin#4 = sawtooth, #7 =drives yoke) to Vcc or ground, or an open loop, and when the IC's thermal protection is activated; Pin#8 goes to 5 V when the guard is activated. Aside from this, see if your new IC is overheating. If so, first check if Vcc at pin#3 (usually 15-18 VDC) has any AC ripple (bad filter cap). Also, off the flyback supply at pin#6 (usually 27-36V), check the current-limiting resistor and cap on that line. Sometimes, the aging of components requires that this resistor's value even be increased somewhat from the original value, until the TDA8351 no longer runs excessively hot.




QUESTION NO. P1026-7: Applevision 1710AV, unit is dead with no video, no HV. I know there is a warranty extension on these but I have a customer who is 200 miles from warranty station and is willing to have me repair it IF I could get some help. Does anyone have any experience in component level repair?

The biggest problem you face is APPLE PROPRIETARY COMPONENTS. Apple has released no information on this monitor (I know I have looked). Apple will ship an empty box with a call tag to the customer so he will not have to drive 200 miles. The average turn around time is 10 days.




QUESTION NO. P1021-1: I need a VEY09P RGB output IC to suit a TEKTRONIX 119-4980-00 monitor as TEKTRONIX will not supply parts.Can you suggest a source for this IC,either in AUS or USA? Monitor is made by Matsushita, who also will not supply parts.

Both Panasonic and Viewsonic use VEY09P in their own monitors, such as Panasonic's C-2192P (chassis# 21HV4S), or Viewsonic's 21PS (2182PS). I cannot speak for Australia, but US Panasonic distributors are usually willing to supply VEY09P (having stock is another matter). Did you tell the Matsushita sales rep your unit was a Tektronix? Tektronix would be an OEM client for Matsushita, and manufacturers often refuse to sell spares that might undercut their OEM clients, even if they sell the spares for their own models. In the US, CCS (Computer Component Source) is one source that stocks VEY09P, US phone is 800-356-1227, Int'l. phone & Fax 516-496-8780, -8784. Viewsonic also supplies VEY09P for its monitors, 800-888-8583; 909-598-8673; email




QUESTION NO. P1013-9: I have a Sun Microsystems monitor model GDM-20D10 that is not powering up. Could anyone tell me where to locate any information on the operation and layout of this beast?

This is the same as the Sony GDM-20D11. You can get the schmatic from ANATEK, or MI TECHNOLOGIES.




QUESTION NO. P108-8: I am working on a Dell D1728-L5, Video comes up Dim (Flyback OK). Have checked caps, LM1203. I do not have pin out for Sencore CR70. If not tube, can someone help?

If you have a CR70, you use socket 3, video 2, bias 100v, filiment 6.3v.




QUESTION NO. P102-5: I have a Radius PrecisionColor Display 20 Monitor. I have been able to make adjustments with both outside and inside controls. However, I cannot find an adjustment for screen image rotation or scew. Right now, the image is tilted about 1/4 inch clockwise.

You need to loosen the yoke and readjust it.




QUESTION NO. P1014-4: I have three Link LM1791DES monitors with the same problem. Each continiues to blow the BU2525A yoke drive transistor. I have replaced the transistor and associated caps and the yokes ring out ok. All geometry controls work and there is no distortion of the picture.The units will run (hot) for about a week before the yoke driver blows again.

I do not know that brand - but be sure that BU2525A is the original HOT! Subbing Japan types (2S..) with European (BU-) type HOTS has not always worked for me- though the newest ref. tables say so. (BUs worked at textmode but fried at VGA and above).- Maybe you want to download the datasheet of BU2525A from Philips semiconductor and see for yourself.- Quote New generation, high-voltage, high-speed switching npn transistor in a plastic envelope intended for use in horizontal deflection circuits of large screen color television receivers(!) up to 32 kHz(!). Other than that, I would check for bulged caps in deflection (but that should cause abnormal picture size in the first place) and the flyback being cool (maybe ring it). What about the HOT's base drive signal? Schematics would be ideal for checking that, but anyway at the end of scan there MUST be a clear and SHARP edge for the HOT to shut down properly. (neg. spike at the end of scan going >5V below GND and the base stays negative until HOT is triggered again). Look for any cap (parallel to a resistor) driving the base of hot from drive transformer- even on (slow) TV-defections if this one loses capacity the hot fries. Maybe it is even the cap filtering the supply at the primary of the HOT drive transformer that has gone. That would reduce AC current through primary and thus weakening/distorting current@secundary thru B-E of HOT.




QUESTION NO. P106-9: I have a Samsung Syncmaster 3NE monitor Model No. CVP4237L that I am repairing. I now have the monitor working after replacing the HOT. I need to do a basic alignment and I would like to know what the FBT B+ reference voltage should be. I have set it to 90V, is this correct?

The B+ adjustment for the Samsung 3Ne monitor is: Turn on monitor and display a full white screen at maximum brightness and contrast. Connect a DVM from TP1 - +150 volt (beside T402 the FBT) and ground. Adjust VR601 and set to 150 volts. Your guess at the 90 volts was close. It is about 87 volts.




QUESTION NO. P930-8: I have a Philips FSR871CV monitor (C2082-DA) where I have located a blown IC. Need help to identify U4 on the Low level signals board. It is a Texas 8 pin IC but the rest is not readable. Any other ideas why this IC did blow?

In an Epson unit that is also a Philips/FIMI chassis, the U4 on the low-level signal daughterboard is a Texas Instruments TL072CP dual opamp.




QUESTION NO. P1013-2: Apple monitor, m/n 1787, fcc id BEJCA453, Goldstar chassis # CA-20. Unit is dead, looks clean inside with low hours.

Check the fuses, including any solder-tail ones mounted on the board itself. These often blow due to the degaussing posistor, their value is marginal. Replace fuses with 2.5 Amp slow-blow types. If the fuse still blows, try detaching the degaussing posistor and powering up. If the fuse now survives, the degaussing posistor may need replacing.




QUESTION NO. P929-3: I have a 1993 Dell Vi1428U monitor with a fast flashing power led, no high voltage. Speed of pulsing is similar to an unset VCR clock display. Monitor looks very clean, no burnt components, no cracks on board. Any idea? Power supply?

Listen carefully to the power supply. If it is ticking or chirping, suspect the HOT. If not, check the video connector pins (PC end). A bent pin(s) that disables sync. signal(s) will place the monitor in power save mode if it is so equipped.




QUESTION NO. P107-5: I have a monitor Addonics 142 LR that loses one color after 20-30 minutes! What could be wrong?

My first guess would be poor solder on the CRT neck board or any other board the video signals travel through. The CRT neck board runs fairly warm so it is subject to heating/cooling stresses that crack solder as well as make the failing connections intermittent. I also find it worthwhile to spray contact cleaner into the video connector (PC end). This is not likely your problem but I have seen colors change their level because of dirty pins.




QUESTION NO. P930-3: I have a problem about monitor for vehicle inspection system manufactured from France (Philips) model muller bem. The problem is vibration images. What should I do first?

The first thing I check is the big electrolytic cap after the bridge rectifier at the primary end and then the electrolytic caps in the HT line at the secondary side.Check for liquid near the caps. Or touch their legs with the soldering iron and if you smell something really nasty, that´s it.




QUESTION NO. P107-2: Can anyone tell me the correct values and power ratings of R109 and R113 on the deflection board in an Apple/Macintosh M3502 monitor?

In the M3502, R109 = 22 ohm/ 2 Watt; R113 = 10 ohm/ 3 watt




QUESTION NO. P103-1: I have a MAC 21" monitor with horizontal problems. I am looking for the value of the resistor R113. Can anyone tell me the value?

IF your 21" is Apple model M3502, not one of the (several) third party makes, then R113 should be 10 ohm, 3 Watt.




QUESTION NO. P102-10: I have an HP monitor FCC ID No. A3KM043. Location 7402 Vertical IC. Can anyone tell me the part number?

If the FCC number is truly A3KM043, the Philips CM2099 monitor has the same FCC ID number, and the vertical deflection IC in that monitor is TDA4860, a 9-pin SIP. If the FCC should be A3KM039, then an Apple M9102LL/D, with that FCC ID number, the vertical deflection IC is TDA4860, a 9-pin SIP.




QUESTION NO. P101-6: I have an HP monitor FCC NO A3KM043 Model NO.D3858A. The Vertical IC was burned out, I cannot read part number at location 7402.

The Philips CM2099 monitor has the same FCC ID number (A3KM043), and the vertical deflection IC in that monitor is TDA4860, a 9-pin SIP.




QUESTION NO. P104-6: I am working on a PB1512sl FCC ID BEJCP510 (Goldstar) monitor. It has an intermittent problem with the screen brightness wavering which also affects raster size and focus slightly. I can mimic the problem by wiggling the screen and focus controls. The symptom does not seem to respond to vibration or freeze spray. Am I correct in assuming this is a problem in a voltage regulation circuit, and do you have a suggestion as to suspect components?

Wiggling the screen focus controls causing the problem would indicate a problem either with the physical controls (that is FBT assembly) or the connections from the fbt to the pcb.




QUESTION NO. P105-5: I have an NEC Model 3FGx with ZD520 and Q512 burned beyond recognition. What are the part numbersof these two components?

Q512 is a 2SK752, ZD520 is a RD8.2.




QUESTION NO. P104-8: I have an Acer 7176I which is all dead, not even light in power LED (the fuse is ok).

Sounds like smps failure. Have you checked the H.O.T.?




QUESTION NO. P103-5: I have an AcerView 17" monitor, model 7176I, FCC id JVP7176I. The screen is out of focus (evenly across the entire screen image), but I cannot find the focus pot on any of the three PCB boards.

There should be a pot on or connected to the flyback transformer. If not, you will find it on the crt pcb.




QUESTION NO. P930-4: We have a problem finding flyback transfomer for monitor model muller bem. Charactheristicof flyback transfomer model DIEMEN 95-22 HR 11P 6362-01

For information on HR Diemen flyback transformers, contact HR Diemen in Spain for assistance, either by email at, or on-line assistance at http//




QUESTION NO. P928-5: I have a Mitac 17-inch monitor model# m1758. The problem is when monitor is turned on, you can see arcing all around picture tube dag .The monitor works just fine except the focus is a bit blurry in the top left corner. Can not seem to find what would cause this problem.

You might want to try using TV CORONA DOPE (GC part # 10-5002). Remove the second anode and repaint the tube around the hole. This may help your problem.

Arcing around the dag coating is indicative that the ground return some how is open. Either the dag coating has failed or the ground strap return to the chassis ground has opened. Having poor focus in only one quadrant of the screen would indicate that probably something within the crt has moved. If the focus in all the rest of the raster is good then you should be able to rule out the focus/hv supply as the cause. Is the purity also affected only in the same area?




QUESTION NO. P925-6: I have NEC JC-1531VMA monitor with problem. Both sides of picture are bowed outside ( ). Picture is clean. Adjustment from the front panel in service helps slightly.

The common problem that causes this symptom is that C561 = 470uF on the main board can leak electrolyte, damaging traces on the PC board. Remove the cap and check underneath: if this cap leaked, you'll need to clean the board well, check all nearby traces carefully for damage, and to jumper any damaged traces. Even with no loss of continuity, leakage onto the trace from the wiper arm of pot VR403 to pin# 8 of board# PWE317E can actively cause problems, so you may need to actually CUT that trace at both ends, and jumper between the cuts. Note, the leaky cap may actually test good, but replace it anyway with a 50V cap. Cap C557 can also get leaky and should get checked, too. A bit of conformal coating or lacquer on the PC board after cleaning well can be a future safeguard. Secondarily to this problem, if it still will not adjust, and you're sure you caught all the damaged traces, check IC4E2 and IC4E4 on board PWE-317E, check that there is 53.5 Volts across resistor R409 on the main board, and check C523.

There is not 53.5 V across R409. It varies with the witdth of pix as low as 27V to 35 Volts.




QUESTION NO. P925-2: I have five MAG DJ530 monitors (model no. XBO504-01 / FCC ID # IAWXBO504) all were made in early 97. All are dead no power no led (green or amber), HOT is OK. Could this be an eeprom problem? HELP!

Check the regulator IC in the power supply for the 5 Volt line, and see if it is outputting 5 Volts. If not, replace it. If the regulator IC is a 78M05 type, upgrade it to a 7805 type.




QUESTION NO. P922-7: I have an Apple M1823 that would not fire at all. I determined that the flyback was bad, and replaced it. Now it fires up briefly, and then the orange light just flashes. It has a good signal coming in with both h and v sync the proper frequencies. I have determined that the horizontal sweep transistor, Q512, is not getting any voltage on the collector. Q511, IRFI9630, had 50 volts on the Source and Gate, with a signal that does not really look good, but the transistor is not switching. I am not sure if the problem is insufficient gate drive, or if the voltage is wrong or something else is wrong.

Check if any of the picofuses (PS500, PS501, PS800 = 1.6 & 1 Amp types) are open. If Q511 is leaky (may test OK), replace it. Also check R851 & R868 = 2.2K, C822 = 470pF/2KV, D504, D824, D825. If still shutting down, and HV is not over 27 KV, check out/replace IC404 = TL082 opamp; check out/ replace IC801 = 4049B CMOS logic IC.




QUESTION NO. P921-8: I have an IBM 8512-003 VGA monitor that has a high pitch sound coming from the power supply. The picture is wavy, but is still very clear. Could anyone help me with a remedy to this problem?

First, replace C120 = 10 uF in the power supply, use a 105°C cap if you can. Also check fast recovery rectifier CR105, and, near the flyback, 3 Amp, 600 Volt rectifier CR212.




QUESTION NO. P919-3: Mitac L1450PD monitor. At switch on the power supply output is low at about 80V and the unit makes strange noises. If it is left like this for 20 seconds, switched off then back on, the unit will work fine for the remainder of the day. I have checked the caps in the primary and secondary of the power supply with a ESR meter and changed the faulty ones but the problem persists. Any suggestions?

In later production runs for this chassis, the manufacturer upgraded capacitor C926 from 100 uF to 220 uF. Does your unit have this upgrade?




QUESTION NO. P925-5: We have several IBM G50 and G41 that have HV problems. The HV leaking from the FBT. First we suspect the FBT itself but we are not sure. It could be that the HV is too high. The picture is OK.

Reading your question states that hv is leaking from the fbk. This would indicate to me that the insulation of the fbt is breaking down causing a path to neutral for the hv. Only cure that I have found that works is to replace the fbt assemblies. You may try applying a sealant to the fbt but I will bet it will not stop the short.




QUESTION NO. P915-7: I have an Apple monitor model m2943 fcc # bjmcm15vb. The unit runs for one hour then shuts down, green light stays on. I replaced pwb-1822, no fix.

This unit may have a factory extended warranty. These units were LEMONS. Check out Apple'S web site for more details.




QUESTION NO. P923-4: Could anyone tell me the spec of an oldish Sony monitor model GDM-1952? I have also seen these badged as IBM's, and neither of them will sync from a vga card.

A lot of these units are fixed mode VGA not Super VGA and will only run on 640x480 mode.




QUESTION NO. P919-6: Monitor Model M152 PNLD, made by S.A.M. GmbH FCC ID IQX93C 1564. This model has a dim picture on Windows 95 opening screen, for example. But when I click on shut down, the display changes to normal. I have replaced the video ic LM1203 but no difference. Can anyone suggest a solution or source of circuit info?

This looks like a video card and/or video driver issue rather then monitor problem. There are two ways to find the guilty party 1. Restart PC to real DOS mode (click on Start, Shut down, Restart in DOS mode, OK). After restarting, at the DOS command prompt, type in dir/w and hit Enter button or start one of the old DOS based game 2. Connect the monitor to another, known good working PC and power it up. If you have good quality picture using 1), reinstall video drivers for your VGA card. If no change but had a good picture using 2), change VGA card.




QUESTION NO. P919-8: I have a monitor Compaq model 420 with the problem that the display becomes squeezed, which curve at the both sides. Any comment?

Sounds like the main capacitors in the 115V power supply. You can jump them with the same values or pull them and test them. But you probably have one or more going bad.




QUESTION NO. P918-4: I have an older, Sony MultiscanHG 17 inch monitor, it turns on only when it has been off for a long time (many days). If I try to turn it on a day after I used it, it makes a whistling sound that grows in pitch, stops, and the power up is stopped. Would somebody out there give me a clue on where to start this repair?

Heat the set up and let it fail. Leave the set on and hit the capacitors in the high voltage power supply (around the flyback) with freeze spray. If there is no response, try the main power supply. Sounds like a capacitor somewhere in the set is leaky and after a while becomes sensitive to heat and voltage.




QUESTION NO. P93-8: I am working on a CTX monitor model 1560Lr. After powered up for 30 to 45 minutes, the pincushion starts to vary by itself and then the screen flutters horizontally. We have repaired many cold solder joints but nothing has helped. Has anyone seen a similar problem on this model?

Hit all of the capacitors around the pincushion and flyback with freeze spray. If it is good when first turned on, then probably a leaky cap.




QUESTION NO. P923-6: I am new to the business of monitor repair, and I am currently working on four Applevision 1710 displays, FCC ID# BCGM2935. All four have the same problem, that is, they power up (LED is green), the high voltage is ok, the CRT charges and remains charged, but the monitor will not display anything (screen remains black). Working on one of them, I replaced electrolytic caps CF1, CF2, CF4, CF8, CL49, with absolutely no results. Can someone please help?

The Apple 1710 model requires information from AppleVision software drivers in the computer, uploaded via the video cable, or you get the "no video/green LED" symptom. In addition, many of these units, those with serial numbers from SG522xxxx up to SG628xxxx, have problems requiring a repair under Apple's extended warranty program, available until 12/31/98. To get the details of how to re-set the display with AppleVision software, or how to qualify for the extended warranty service, go to webpage http//

The problem seems to be on the crt board\processor board with bad solder and mainly on the surface mount components. I have had luck reworking iv2, iv4, iv6.




QUESTION NO. P918-7: I have a MAG DX17 monitor with a bad transistor at location Q116. It is marked as a K1378. ECG and SK did not have it listed. Any ideas as to what might be a cross for it?

That should cross to an NTE1378, as I had to replace this in my Gateway 1776LE unit.

2SK1378 is a Toshiba MOSFET, rated 400V, 10 Amp, Rds[on] < 0.55 ohm, 125 Watt. For the DX17 monitor you have, IRF740 should cross for 2SK1378 Mouser (800-346-6873) lists IRF740 for $2 - $3, depending on manufacturer (EXL, SGS, or Harris), and TechAmerica (800-877-0072) prices similarly. If you prefer using 2SK1378 itself, B & D Enterprises (800-458-6053) lists this for $8.58 or MCM Electronics (800-543-4330) for $4.38 (MCM's minimum order is higher than B & D).




QUESTION NO. P98-5: Tenemos un monitor IBM 6543-302 con insuficiente e incontrolable anchura horizontal, estando a la vez fuera de frecuencia. ¿Podeis ayudarnos?

La averia que tiene ese monitor es muy comun tienes un condesador electrolitico seco, normalmente llevan tres condensadores cerca de la deflexion horizontal cambialos los tres y ya esta. Para encontrarlos sigue los cables del yugo de deflexion de horizontal.




QUESTION NO. P917-2: I have a CTX CVP 5468 NI with a horizontal sync problem. Monitor came in for flickering picture, seemed like bad solder connections. Resoldered. Searched Dejanews. One reference to the 5468 said that Anatek had an extensive database on this problem? Where can I find it at?

Regarding the monitor repairs database, you may mean Anatek's new DataDirect CD, general repairs database, or the Resolve Monitors Repair Database (see info on this website). In the meantime, try freezespray on the LA7851 IC in your CVP-5468NI, and see if it affects your sync problem.




QUESTION NO. P812-8: I have a Packard Bell PB1412SL that came in with a shorted H.O.T. (2SC4619). I replaced it with a ECG2353 (2SD1881). It works fine except when it goes into low power standby, it blows the H.O.T. again. B+ and Vp-p are normal and a quick check of surrounding components yields nothing. Customer becoming upset. Any thoughts?

I had the same problem when tring to use the cross ECG 2353 for the Toshiba C4619. Seems like the chassie design does not like the ECG 2353. If you look at the knot on the 2353 it will work with most applications. But not this one. Use the 2SC4619 and you should be fine.




QUESTION NO. P94-1: I have a problem with TELEFUNKEN chassis 615 A1. Switch on is correct but no image, the screen is black, the horizontal power transistor does not work. I checked the driver but it is OK and replaced the C.I. TDA 1940 oscillator H. but it does not work. I checked Q482 it is OK. My big problem is I do not have a scope.

We need more info. Do you have all of the smps voltages?

You can try COMPUTER COMPONENT SOURCE at 1-800-356-1227.




QUESTION NO. P824-8: I have a question regarding a 17" monitor. I need to know where I can find the transformer (serial inductor) that generates the B+ to the flyback. The brand of this monitor according to what I found on the back cover is Fair Electronics, new to me.

You could try Conputer Componet Source at 1-800-356-1227.




QUESTION NO. P812-6: I have Premier aa1450 (fccid# mm3cj-480n) VGA monitor. The company that manufactured it is Chang Jun Technologies. I cannot find any way to get a schematic for it. R522, which goes to pin 3 of the flyback, disintergrated just leaving a scorch mark.

It may be a low ohm fuseable resistor (1 to 10 ohm). To help further we need to know what circut it feeds (ie vertical, pincushon, etc.)




QUESTION NO. P819-6: I have a CTX-1565D that will power-up, but will not show any video. The CRT heater is working and there appears to be high voltage. I have seen other CTX monitors with a similar problem. Do these monitors have a typical failure mode? I do not have schematics.

For 1565D usually there is need to resold CRT socket. Check G1 and D2 anyway.




QUESTION NO. P827-5: I have a CTX CVP-5468A monitor with low brightness and slightly too-wide display. The owner's complaint was only the low brightness. He said this happened suddenly. I do not know if the over-width happened at the same time. There is barrel distortion on the right side, and the top and bottom are slightly wavy. Only the left edge is dead straight. The monitor is stable, hot or cold. Nothing looks fried. The B+ is correct at its marked 104v. The HOT and flyback run cool. Screen and focus pots are paint-locked at factory settings. The auto-sync works well. The colors are very good. Linearity good. I am trying to figure out what single "sudden" failure could account for these symptoms.

Horizontal size and brightness change at the same time if HV is wrong. Check HV regulation circuit.




QUESTION NO. P826-10: I have a NEC 4FG, Model jc1531 VMA, with bad side pin Cushion )(. I already checked C561 for leaks but do not see any. What else can I check?

I cannot tell if your inspection of C561 for leaks was good enough. Did you read the Monitor Answer# P527-4, including the part about C561 seeming OK? Did you do everything that answer indicates? Checking continuity of traces and cleaning underneath C561? Jumpering the trace from VR403 to PWE317E? Testing the IC's on PWE317E?




QESTION NO. P817-3: I need information about an IC (included in a monitor 4FG,15"Nec) VPS08N. I have tried many different sites, there was no information. Can you help me to find datasheet for this IC, it is only for testing purpose, if the ic is OK.

VPS08 is a Sanyo 3-channel, 80 MHz CRT video output driver. It is obsolete, so the Sanyo website ( does not provide its datasheet. But you might download the datasheet for VPS10, which has similar package and voltage ratings, though rated for 100 MHz. VPS12 and VPS13 also exist. In the meantime, you might also check the traces beneath your VPS08N for corrosion due to leakage from cap C793, which is a common problem in NEC 4FG's.




QUESTION NO. P98-9: I am working on a GVC 1450C that had a blown HOT transistor. The ID # was a C4916 which crossed to a ecg 2353 with a note stating that it might not be the same electrical or mechanical match but works in most cases. So I throw one in and bring it up on a variac, everything seems fine. I run the monitor for a few hours turning it off and on every so often, worked fine. The customer takes it home plugs it in and it dies. Is this replacement part one of the few that will not work with this application or is there something else I am missing? I noticed that the ecg 2353 and the nte 2353 are not exactly the same. Wonder what the values were on the original C4916?

It is a risky proposition using "universal" type subs to replace HOTs; you cannot just rely on the usual Volt/Amps/Watts ratings to pick a substitute. Differences in gain, capacitance, and inductance will affect how easily the HOT can be driven, so you just cannot assume that even a higher-rated device will sub for the original in the particular circuit in your unit. A beefier HOT (or one with the same Amp rating but insufficient gain) is usually harder to drive, and will overheat if underdriven by the existing drive circuit, as its saturation voltage will be too high. A device that is overdriven (or has too much gain) is too slow to turn off and will dissipate excess power, while a device that turns off "too fast" just may suffer excessively high inductive voltage spikes. With regard to 2SC4916, that is a Toshiba device, rated 1500 Vcbo, 7 Amp, with an internal damper diode. Union Electronic (800-648-6657) sells 2SC4916 for $5.08, MCM (800-543-4330) for $5.45, B & D (800-458-6053) for $6.54-- how much did that ECG2353 set you back? When you HAVE to try a universal sub, check the HOT's case temperature right after running it, and be sure it is not running hot, before letting it out of the shop. A good HOT choice generally does not run too hot.




QUESTION NO. P98-10: How can I determine who the original chassis manufacturer of a monitor is by using the FCC ID# on the back of a monitor?

Locate a link to the FCC data base and use the information on the back of the monitor to confirm source of origination. Database is very easy to use, just have to type in the ID info and it will come up with the material, if stored therein.

The first three characters in the FCC# determine the true manufacturer. You can identify them either by going to the FCC site at http// and downloading the ZIP datafiles of these three-character ID's, or else by using the FCC's online search engine at http// Note that the same manufacturer may have several different three-character codes assigned to them. The remainder of the FCC# identifies the individual chassis. Theoretically, every time a manufacturer produces a new chassis, or even modifies an existing chassis, it requires re-certification by the FCC, and the chassis gets issued a new FCC#.




QUESTION NO. P812-7: I have a Packard Bell 2020 monitor which has a brightness problem. The bright ness control has absolutely no effect at all. The control is an analog type of control and I have checked it with an ohmeter, and it measures good. Someone told me it could be an open transistor or restor near the flyback. Has anyone seen this problem before? I am not sure where to start looking. Monitor is 15 months old.

I was working on a lot of 2020 two months ago. The common problem is no panel control, sync lost, will not start, buzz, etc, I only changed epromm 93c56 and, for one only, I put a Proc Zilog z0861404psc. You need after to put a shield ground on two parts, because they have a risk of static discharge(it is the problem). Call Parts at LJ Enterprise ( The price for eeprom preprogrammed is about $10,and zilog $20.

If there is a voltage on B+ around 50V then you should change IC I804(UC 3842). Important, there are two IC UC3842 in this kind of monitor. I804 is NOT in a main power supply.




QUESTION NO. P824-3: Sony GDM-20E01 20" computer monitor; has vertical smearing (bad focus) in about the middle third of the screen. The smeared band is vertical in orientation on the screen. "Focus 2" control starts to clear up the problematic area & then the pot reaches its end before it pulls focus in (clearing this section un-focuses the good areas though). Bad focus voltages? Guns? Tube?

Check the focus voltage and HV. Focus should be roughly 10 to 15% of anode. If this confirms then you probably have a bad crt. Also confirm proper B+. If it is too low, the beam current, hv and focus will be affected.

This problem must be in dynamic focus. Mostly this failure is caused by IC404 on the Main-Deflection board.




QUESTION NO. P812-11: I have a GVC M1448L color monitor with a burned R386 (next to the TDA1675A) and an exploded C802 (at front of board). Does anyone know the value of these parts?

R386 is 10 ohms, and C802 is a 47 uF 35V electrolytic capacitor.




QUESTION NO. P816-3: Compaq Qvision 480P. Raster gets progressively brighter until retrace lines are visible. Does not seem to be the flyback. Anyone familiar with this problem? Quick answer would really be appreciated.

This is a common problem with Qvision 200. You need to replace "brightness and focus block". It cost about $80 to $90. Good Luck.




QUESTION NO. P816-6: MAG MX17S monitor problems. I found cold yoke plug joint which caused horizontal deflection transistor Q503 (C3897) to short. After replacing it with NTE2354 I have a picture but pincushion circuit is not working at all. Picture looks like hourglass and pincushion trim pot is not responding. Could someone please point to the pincushion circuit components that may be at fault?

I found an answer to my problem. I had to replace two darlington transistors Q909 and Q506 (original 2SD799, replaced with available 2SD1409). Pincushion control works now. I still have a distorted picture and raster on the very top of the screen. It looks like N-S pincushion problem -barrow shaped top of the screen only. I cannot find any adjustments (trim pots or coils to compensate for it).




QUESTION NO. P819-4: I have a Wyse Model WY-60-02-02, that was showing H scan problems before dying completely. C205 has burst and R214 and C206 are burnt beyond recognition. Values for R214 and C206 would be appreciated, as well as pointers to any other potentially failed parts, (I have no schematic).

R214 is 10 ohm 1/4 watt. C206 is .22 mfd 100 volt. Check for bad yoke.




QUESTION NO. P729-3: I have a CTX Monitor Model CTX 1760 DF. The horizontal size is too wide and cannot be adjusted using the digital control. Even adjusting the horizontal size pot in the main board will not help. Could you help me on this problem?

Try to remove dry glue in supply unit, and in main board (right front). This glue goes to resistive when dryed, very common on this model. No adjust on horizontal and pie crust on screen. Resolder connector in supply.




QUESTION NO. P729-4: I am wondering why the damper diode of the IBM G70 monitor keeps shorting. A new diode (BY359F 1500) will bring it back to life, but only for a few minutes. The diode shorts, the power supply stops. Could you tell me what the original diode for cr301 should be? IBM G70 model 6544-403 part number 96G1870 FCC ID AN06544.

Diode must be at least 2A 1000V. Any diode less than that will blow.




QUESTION NO. P86-1: I have a 15" FS SVGA Monitor with some troubles. I am having a little trouble figuring out who it is who actually makes it and how to fix it. I have seen many monitors with this same appearance (an example would be the Princetons and KDS monitors). This display says "VIDEAL" on the lower left area and on the rear panel the sticker says ASTRAL MICROELECTRONICS CORP. FCC ID# IJEPV-564D PRODUCT# PV-1564A MODEL# PV-5640 MFG DATE = DECEMBER 1996. I am guessing that the trouble is in the high voltage section but I am probably wrong. When turning it on, the power light comes on and there is a slight static sound (like the HV is coming up) but I can not feel anything on the display. I have done monitor repair before , but have never done one with this "DIGITAL CONTROL CIRCUITS" getting in the way.

The FCC number is your best indicator. This number will tell you if the chassis is the same as that from another brand name. It also is needed when dealing with brands such as AST, Gateway, or Packard Bell, that market different chasses, from different manufacturers, under the same model number. For example, a PB "1412SL" or "1512SL" can be made by several different manufacturers! This makes trouble-shooting such models, or relying on "Tips Databases" for them, difficult. In your case, the "IJEPV-564D" indicates this chassis came from Essex Monitor Corp., Taiwan, and is the same chassis as the Proview PV-564D. With regard to your problem, first check if the CRT is a Samsung. The Samsung CRT's in these chasses are notorious for going bad. If the CRT is OK, and you are getting HV but no static on the screen, see if the CRT filaments are lit and the associated circuitry is OK. If they're not heating, the electrons that should go to the face of the CRT will never get emitted. You might also check the 12 Volt supply.




QUESTION NO. P730-10: I have a monitor type Hyundai HM 421 . The problem is that I have a scrolling picture (from top to bottom). I have already replaced TDA 1675A,TDA1180,NE555,74LS86,74LS156 but without any result. Can someone give me some tips?

Check the signal cable for a cracked wire (Vsync).




QUESTION NO. P81-1: I have an Apple Multiple Scan 17 Monitor (M2494) which is overscanning by perhaps 50% both vertically and horizontally. The screen geometry is fully electronic ie. no potentiometers. The Apple literature that I have access to suggests complete replacement of the deflection board, this seems like an overkill. Any suggestions or ideas would be appreciated.

This is a "default" failure for the 2494! Q510 is defective and must be replaced only by the original (FS10SM-16) 8-729-025-94.




QUESTION NO. P83-6: I am working on a Philips C2082 Monitor that reports 'HIGH VOLTAGE Fail' on its LCD. I checked flyback and the high voltage and the -200V that it produces come on very briefly after power-up. Then the voltage collapses. Could it be the beam limiter circuit doing its work (not properly)? How can I locate the faulty circuit (components)? Also which brand is the HOT (THD 400) used in it?

Check fuse 801 (solder type near flatcable to hv-box). If it blows again, most likely the flyback is defected.




QUESTION NO. P83-4: I have a Packard Bell Model 2020 monitor that has no screen brightness. The control has no effect at all. Pot measures good, picture is there and has contrast, but no brightness. Unit is only 14 months old. Anyone seen this and can help?

Check g2 and g1 supply, g1 can be too much negative. Check drive on RGB drive on CRT.

If there is a voltage on B+ around 50V then you should change IC I804(UC 3842). Important, there are two IC UC3842 in this kind of monitor. I804 is NOT in a main power supply.




QUESTION NO. P84-1: I am working on a Daytek monitor, model dt-14xvb, fcc idewboc143xv. Problem is no hv. Power light go on regulator and capacitors arround the flyback and smps test ok. I have six units with the same problem.

Check the TDA1675A vertical IC.

These 14" Daytek monitors seem to come up with this problem quite often. Replace C8062.2uf @ 100v, C8082.2uf @ 100v and C824 @ 160v. These capacitors are located on the primary of the power supply.

I have repaired several with the flyback connnections pulled away from the land patterns. This is done when the flyback mounting screws on the OUTSIDE bottom of the case are tightened. To correctly suck all the flyback pins clear, insert the mounting screws and tighten the flyback to the PCB. Solder all pins and re-assemble as normal. This has happened on the last four Daytek monitors repaired for no HV.




QUESTION NO. P726-6: I have a Visa MC 8960 monitor which works fine, but when I turn off power I'll get a spot in the middle of the screen. I've already changed some condensators on the video board but without any result.

Suspect a fault in the "spot-killer" circuit. This is a circuit that is supposed to kill all the bias to the crts when powered off to eliminate this problem.




QUESTION NO. P81-7: I have an IBM 8513 that blew the HOT transistor after making a buzzing noise. When I replaced the transistor, the monitor has HT voltage but no longer has any vertical deflection.

Prob the vertical output ic and associated rectifier and protect resistor{s}. Prob the ic failed causing an overload which is what caused the ps to buzz in agony before opening the fuse resistor.

Check all power rectifiers coming off the flyback. Perhaps there is a shorted one which powers the vertical outputs. There may be a fusable resistor in series with the rectifier. Also check the electrolytic capacitor on that line too, as well as the parts in the vertical circuit.




QUESTION NO. P726-4: I have a NEC 4fg (jc-1531vma). Someone has worked on this unit before and removed two parts. Need to know values of Q-503 and Q-504.

Q503 is a K699 and Q504 is a B536 with a heat sink.




QUESTION NO. P717-9: I need the horizontal/vertical scanning frequencies of the Samsung SyncMaster 15C monitor. Can someone help me?

The 15GL Horizontal Frequency 30-62, Vertical Frequency 50-100, Max Pixels 1024x 768.




QUESTION NO. P728-10: I have an Applevision 1710, family model # M2935 which does not power up when video signal is supplied from Sencore's CM2125, there is no power on LED. Does this monitor need some type of adapter to power up?

Sencore makes an adaptor #8 or #8f that will turn the unit on.




QUESTION NO. P717-6: We are looking for a replacement diode for D925 on a Micron 15fgx monitor. The number on the diode is BYM26C PH. Anyone have any ideas?

BYM26C is a Philips rectifier, 600 Volt, 2.3 Amp, 45 Amp surge, ultrafast recovery (Trr <30 nsec), with soft-recovery characteristic. The leads are thicker than usual in dia., and manufacturers may install them with long leads, to help radiate heat. If your Philips supplier cannot provide it, the closest US-type rectifier meeting these specs is 1N6628-JANTX, which Arrow Semiconductor lists for $8 each. Or, if you wish to try a cheaper rectifier, HER306 has similar capabilities, but has a slightly slower Trr than these two. HER306 is listed by Mouser (800-346-6873) for $1.17 apiece.




QUESTION NO. P724-7: I have a Gateway ( Sony ) monitor model CPD-17F23 that came in with a shorted horizontal output transistor. I have replaced the transistor and the monitor will try to come on, but I only get about 25 volts on the collector of the HOT. I have checked the other supplies in the monitor and they are all fine. B+ 141 volts, I also have the 75v 45, +5 and switched 12 volt supplies. Has anyone had a similar problem and knows what else is a common failure for this model?

There are only a few components between the reg B+, primary of the FBT, and the HOT. Check the B+ @ the primary of the FBT. If good there then the coil in the FBT is probably bad. If low there then problem must be further back towards source. I should suspect the B+ is low to the FBT caused by some defect between it and the power supply.




QUESTION NO. P722-5: I have a NEC monitor with the model number of JC-1402HMA and FCC ID of A3D9MDJC-1402HMA. On the power supply board PWE-195, resistors R623 and R632 were burned beyond recognition. I was wondering if anyone could please tell me what value they are supposed to be?

NEC maintains a tech support page, with listings of the original parts for its JC-1402HMA monitor, at http// According to that site, R623 is 5.6K, 5%, 1/4W, and R632 is 1.2K, 5%, 1/4W.

R-623 is a 5.6k 1/4 watt and R632 is a 1.2k 1/4 watt. Notice that they are both sitting on pin 14 of IC602 which might also be bad stk 7404. Also check diode D610, transitor TR602 and resistor R624 (1 ohm 2 watt). The DC output at C1 will run anywhere from 53 to 98 volts depending on the mode the monitor is running in. The fixed output voltages at K1 and K2 are +85 and +26 volts respectively.




QUESTION NO. P720-6: I have a Dell Model D1726S-HS that all colors have faded, red is real light pink. Focus and brightness looks good. Customer said this has progressed slowly.

You should test the tube, preferably with the Sencore beamrite 7000 which checks low level tracking. This test when it fails indicates a "leaky" tube which affects contrast and colors - NO way to fix this problem.




QUESTION NO. P720-9 MONITOR IBM 8515 I have replaced a fbt TLF71004D in the 8515-002 model and it worked correctly. The same fbt on the 8515-022 and 8515-222 models do not work correctly. Apparently the boards are the same, without difference. I have tested more fbt and different models but without results!! The fbt is not original, is a copy but works correctly on the 002 model !! Both the model install a tlf71004d fbt.

You should test the tube, preferably with the Sencore beamrite 7000 which checks low level tracking. This test when it fails indicates a "leaky" tube which affects contrast and colors - NO way to fix this problem.




QUESTION NO. P623-9: I have an HP-1512sl Computer monitor with no contrast control. I have checked the Pot, its ok, I have followed the traces over to one of the two large I.C.s and suspect the problem is with one of the I.C.s CRT checks fine on Sencore CRT tester. Has anyone corrected this type of problem before?

You should test the tube, preferably with the Sencore beamrite 7000 which checks low level tracking. This test when it fails indicates a "leaky" tube which affects contrast and colors - NO way to fix this problem.




QUESTION NO. P630-7: I have two ACER 17" 7176i monitors, on one there is no GREEN, so the monitor looks pink, and on the other there is no RED, so the monitor looks Blue. I have checked the output transistors, and the reistors and caps in each color circuit, but have not been able to solve the problem. Any suggestions?

If I am correct, this monitor has a microprocessor that controls the presets of RGB gain. On the processor board, there is a LM-324 in SMD that could cause this failure. The blue level is adjusted at lowest in case of a defect opamp.




QUESTION NO. P720-1: I have a CTX CMS 1561LR which was dead. I replaced the 2SK955 and the ZD101 (1watt) and the HOT. I checked R113 and found it to be alright. Also WHERE is ZD102? I had replaced ZD101 with 5.1V zener. Unit would not come up. I then read the reply to "What is ZD101" and installed 18V,1W zener for ZD101, now the unit "cycles" the relay (green led blinking away madly) at 2hz. Did I damage anything by installing the 5.1V zener, or where else shall I look?

You say you replaced 2SK955. If the FET had shorted, it might also have damaged the 3842 PWM IC. And check resistor R114 = 0.39ohm for value. ZD102 should be on the same daughterboard where you found R113; check values of the resistors and the diodes on this board as well. Bad solder on this daughterboard, especially cracks on the pin connectors to the main board (or on the main board side) can also cause these problems, and need resoldering. Of course, there might be a genuine circuit fault on one of the Power supply outputs, too.

Replace the .39 ohm resistor. I had a similar problem that fixed the flashing LED.




QUESTION NO. P721-5: I am working on a Compaq model #470ap with a burned resistor at location# R201. Does anyone know the value?

R201 = 1 ohm,1/2 W




QUESTION NO. P610-1: I am trying to find two Philips caps for an Apple monitor. The cap values are 11nf @2000VDC, and 5n6@2000VDC. I've tried Newark and other parts houses with no luck. Any suggestions?

I can't give you a precise answer, because the information you posted was so scanty. Philips makes SEVERAL lines of caps with 5.6 and 11 nF values at a 2KV rating, both ceramic disk and film types, all of which are intended for various monitor functions. You didn't post the Apple Model number, or cap location numbers, so no help there. But it is my guess that you are looking at two rather large radial box film caps. If so, these are polypropylene film caps, NOT polyester, and are snubbers specially constructed to handle fast dV/dT pulses. You will NOT be able to sub these with polyester or ceramic disk types, they would dissipate too much power, and melt or self-destruct. There may already be a Philips type number on the cap, something like KP/MMKP376 or MKP378. Or if this has faded, or was blacked out by the manufacturer, note the exact dimensions and style of the cap. With this information, go to the Philips Passive Components website at http// , download the data sheets, and find the multidigit Philips catalog numbers that match your caps. With those part numbers, a parts house or a Philips supplier may be able to help you out, or suggest an equivalent. Cornell-Dubilier is one North American manufacturer that makes polypropylene snubber caps with fast dV/dT ratings; Mouser Electronics is a distributor of their line.




QUESTION NO. P76-2: I am looking for a supplier for the 11nF and 5.6nF 2000Volt philips caps used in a Mac monitor. I have tried several Canadian suppliers to no avail. Can I sub these with ceramic disc caps or do have to have the polyester high temp caps?

I can't give you a precise answer, because the information you posted was so scanty. Philips makes SEVERAL lines of caps with 5.6 and 11 nF values at a 2KV rating, both ceramic disk and film types, all of which are intended for various monitor functions. You didn't post the Apple Model number, or cap location numbers, so no help there. But it is my guess that you are looking at two rather large radial box film caps. If so, these are polypropylene film caps, NOT polyester, and are snubbers specially constructed to handle fast dV/dT pulses. You will NOT be able to sub these with polyester or ceramic disk types, they would dissipate too much power, and melt or self-destruct. There may already be a Philips type number on the cap, something like KP/MMKP376 or MKP378. Or if this has faded, or was blacked out by the manufacturer, note the exact dimensions and style of the cap. With this information, go to the Philips Passive Components website at http//, download the data sheets, and find the multidigit Philips catalog numbers that match your caps. With those part numbers, a parts house or a Philips supplier may be able to help you out, or suggest an equivalent. Cornell-Dubilier is one North American manufacturer that makes polypropylene snubber caps with fast dV/dT ratings; Mouser Electronics is a distributor of their line.




QUESTION NO. P71-6: I have a Premio (made by sceptre) model 566 PN:P-514ca monitor. I am getting no high voltage. HOT and flyback are both OK. Power led does change from amber to green when signal is applied. Any ideas?

Check the horizontal driver transformer drive transistor, and associated components. Confirm there is bias at the collector of the drive transistor and output. Confirm there is horizontal drive signal to the driver and output. Check for any type of unusual loading in secondary of flyback, including shorted yoke or bad crt.




QUESTION NO. P617-10: I have a Dell P1728U monitor here that had a shorted diode (D954). After replacing the diode, the vert IC blew, and I cano't read the number. I suspect that the vert IC was shorted causing the diode to go.. With the vert. IC taken out, the monitor comes up but the LEDs on the contrast and brightness controls flash and the vert. size led is on solid. Can anyone tell me what the part # of the vertical IC (IC401) is?

IC401 is a TDA2006




QUESTION NO. P617-5: Je cherche la référence exacte du circuit noté dans mon cas KA2139S sur un écran Diamond 15pcs.Ce circuit est apparement le préampli vidéo.

Le circuit KA2139S est effectivemment un préamplificateur RGB pour écran. Il est fabriqué par Samsung Semiconductors. Vous en pouvez obtenir la "datasheet" en format .PDF (Acrobat Reader) à




QUESTION NO. P630-8: I have an NEC monitor, ModeJC1575VMA, when powered on the HV is ok, I have a green LED and normal raster when the screen control is turned up. The problem is a "NO VIDEO" symptom. Normal video signals enter the LM2405 I.C. on the video P.C.B but no signal is present on the CRT cathode pins.

LM2405 is a triple CRT driver for R,G, B. I take your comments to mean that there are three video inputs (not blanked) going in to pins 8,9,11, but none are coming out (at pins 5,3,1). This IC is open-loop and fixed-gain, with independent amp circuits for the R,G,B signals. So, if NONE of these signals are coming through, either the IC is bad, or one of its two supplies is down. First, check that you are getting Vcc at pin#6 and Vbias at pin#10; these should be at the very least +60V and +8V, respectively, relative to ground (pins 2,4,7). More typical operating voltages are +80V and +12V, respectively. If either supply is below the minimums, check if there is an internal short in the IC at either of those two pins, if the bypass caps off pins 6 and 10 are good, or if either of the two supplies is not functioning upstream. If both supplies have good voltages, and their bypass caps are good, the IC itself is probably gone.




QUESTION NO. P630-10: I have a Sony CPD-1320 monitor in the shop which the customer complains that it works fine in DOS, but won't sync in Windows. I don't have that problem on my computer. It works fine in DOS and Windows at 640X480, but at 800X600 the image is shifted left, and at 1024X768 the picture rolls. There are no user controls. I've changed every IC on the main board and checked all caps. Any suggestions?

You have been beating a dead horse. The Sony CPD-1320 monitor was designed with a maximum resolution of only 640 by 480, 60 Hz. This is probably your customer's problem too.




QUESTION NO. P616-6: I have a Monitor ACER 7176N and R458 is burned. I need know the value of R458.

R458 = 2.7 ohms.




QUESTION NO. P618-6: I have a viewsonic 17gs dead it uses a surface mount board. Any ideas on where to start?

Do not be intimidated by all the smd devices. Check out the power supply and regulator as well as the horizontal output & HV. Unless the unit took a major overload the probability of damage to smd devices in minimal.




QUESTION NO. P618-1: I was working on a Gateway 1776Le 17 inch with no video. Replaced R177,C120,C123 andHOT with an ECG 2354. R181 and Q116 checked O.K. Monitor came up and worked beautifully for about 45 minutes then the screen started closing in horizontally until it went out. HOT is shorted again and the monitor just clicks now. Did I use the wrong HOT or could something else be killing it?

Did the fbt get really hot before blowing the transistor, then the fbt is probably bad, or you have a severe overload in the derived supplies. Otherwise check the regulated B+ to make sure it is not to high, running on a variac at reduced voltage may help diagnose.

Those parts which you mentioned have a nasty property: if one of them goes bad, that can then take out any of the others. But one more common-failure part that you didn't mention needs to be added to that list: L105, a somewhat tall, 4.5 mH loading coil connecting to the B+ input of the flyback. Usually when the HOT shorts, L105 gets cooked, and the bad L105 can then do in new HOTs, etc. Replace it if it looks slightly discolored or bubbled, or rings badly, or even on general principle. L105 is Mag Innovision (800-827-3998) part# T*I-281-103-UO, and suppliers like LJ Enterprises, MI Tech, CCS, et al., may carry this coil too, roughly $12. And then go back and test all those other parts once more, since you've had yet another failure. Aside from L105, if bad B+ regulation is giving the HOT excessive voltage, see if Q116 is leaky now, or if C334 or D116 or the flyback has gone bad. The usual Q109 transistors used in these Mag units are 2SC4747, 2SC4924, or 2SC5129.




QUESTION NO. P616-9: I have an AST Vision 5L that has lost horizontal widht and pincushion control. HWat are the most likely culprits?

Since you did not post the unit's FCC number, I do not know the true manufacturer, so I can only say that IF your Ast 5L is one of the Daewoo versions of that model, possible culprits could include IC901, and diodes D502 and D503.




QUESTION NO. P69-1: I have a NEC monitor model 3FGX which had a focus problem so I changed the Flyback. The monitor seemed fine for a while then it would not turn on anymore.

Check out the HV-adjust pot VR516, a silicone-sealed 20K ohm pot near the flyback. These are factory-preset for each individual unit (hence the silicone), so your new flyback may need that setpoint changed. These pots can also go bad and cause shutdowns.




QUESTION NO. P64-4: I have four CTX VL400 monitors that keep shorting the HOT , the flybacks are ok.

If those VL400's have cap C722, a 47 uF/50V electrolytic, near the HOT, that cap commonly gets bad ESR and affects the HOT. With that many units down, some may also need to have Q406, Q407, and FET Q410 checked for leakiness or shorts.




QUESTION NO. P68-11: I have a CTX CMS 1561LR which was dead. I replaced the 2SK955 and the ZD101 (1watt). Now the unit stays on for about 90 sec. I checked R113 and found it to be a 100 ohm resistor. Also what is the value of ZD102?

There seems to have been a typo in your earlier response. CTX service dept. had issued a recommendation that ZD101 be upgraded from the original 18 Volt, 0.5 Watt zener to a 18 Volt, 1 Watt zener, to avoid fuse failures. ZD102 is 5.1 volts at .5 watt.




QUESTION NO. P527-6: I am working on a MAG DX700T - shorted horizontal transistor 2SC5048. I need value for R173 which is unreadable.

For the Mag DX700T, my notes say R173 = 1 ohm.




QUESTION NO. P61-6: I have a Dell D1528LS with no raster, HV is 26Kv, Heater is 6.3, but G1 is about 20V more negative than it should be after doing comparison to a working unit. It appears that the processor could be holding the tube


If this Dell 1528LS is a Lite-On unit, with the Zilog Z0861404PSC processor, that IC is known to give problems, and shutdown to black is one possible symptom. Sometimes freezespray or heating can reveal this IC as a culprit. These IC's have a number stamped on the chip ("Zilog xxxx") indicating the programmed version. So a replacement Zilog (~$20) must be compatible with that version, or you won't have access to control functions like pincushion adjust, or won't sync, etc. Try LJ Enterprises (800-627-8755) or Partronics (800-232-3055) for help on this aspect.




QUESTION NO. P61-5: Goldstar CMT-4568 Chassis NC-06X1 No verticle deflection. Output from IC02 pin 6 is flat +5v DC. Is the problem likely to be with IC02? If so, can you assist with e replacement cross-reference. The chip is labeled NEC D6104C.

The full number for this NEC chip is UPD6104C. Try Union Electronic Distributor, Illinois (800-648-6657) or MCM Electronics, Ohio (800-543-4330) for this IC, both had listed it in their stocks.




QUESTION NO. P527-4: I have a nec multi sync model jc 1531vma<4fg> bad side pincushion. The adjustment does not work. Has anybody come across this problem?

The common problem that causes this symptom is that C561 = 470uF on the main board can leak electrolyte, damaging traces on the PC board. Remove the cap and check underneath: if this cap leaked, you'll need to clean the board well, check all nearby traces carefully for damage, and to jumper any damaged traces. Even with no loss of continuity, leakage onto the trace from the wiper arm of pot VR403 to pin# 8 of board# PWE317E can actively cause problems, so you may need to actually CUT that trace at both ends, and jumper between the cuts. Note, the leaky cap may actually test good, but replace it anyway with a 50V cap. Cap C557 can also get leaky and should get checked, too. A bit of conformal coating or lacquer on the PC board after cleaning well can be a future safeguard. Secondarily to this problem, if it still will not adjust, and you're sure you caught all the damaged traces, check IC4E2 and IC4E4 on board PWE-317E, check that there is 53.5 Volts across resistor R409 on the main board, and check C523.




QUESTION NO. P511-9: I have a CTX model 1760df that has a problem powering at the startup. It takes awhile before it powers good.

Try replacing IC104, 4n36; IC101, tda4605; R129, 47k 1/4-watt; R172, 100k 1/2watt. Also check for bad solder connections in the power supply.




QUESTION NO. P520-3: I have a viewmaster CA 1414VL that i believe might be the same as a KFC CA 1414VL. I have found that IC U502 has had the top blown off it and that R527 is burnt out so that I cannot identify either component. Can someone identitify th part number of the IC and the value of R527?

U502 is a UC3842 which crosses to an NTE 7096. R527 is a 1 watt .22 ohm flameproof resistor.




QUESTION NO. P518-2: I have 2 NEC 14" multisync 4FG model # JC-1531 VMA monitors with the same pincushion problem. The screen has good clarity and brightness and switches to all modes but the sides of the picture are concave )(.

Check C561 470uF/25V could be leaking on bottom replace it with a 470uF/50V 105 DEG.C. if it still does not work check IC552 LM2940CT 12V 1.5-AMP regulator.




QUESTION NO. P514-5: I have a Packard Bell mod# PB8515sv BPCS#010201001 FCC ID# BJMCM15VD which looses the screen size/position controls after it is on for a couple of hours. If it is run in a cool enough area the problem does not occur.

I replaced the High Voltage regulator and it seems to be working fine.




QUESTION NO. P417-1: I am working on a Viewsonic Model 5 computer moitor that came in for vertical collapse. after troubleshooting found defective vertical out ic. replaced, now have picture with terrible found over, can any one help.

Determine the reference designator (ic number on circuit board) for the vert IC and change out the caps that have the same first number in their designator. Generally, the caps closest to the heat-sink are the ones to go bad first. When replacing a vert IC, it is a good idea to replace these caps also, as they are often the souce of the failure anyway.




QUESTION NO. P430-10: I have at several times seen similar 20 inch monitors under the brand/models of PHILIPS.FSR871CV, DIGITAL.PCXAVF4 and COMPAQ.480/480P/481. All give the same symptoms, that is a message on the LCD "HIGH VOLTAGE FAILURE". Apparently the "EHT GENERATOR" a very expensive and hard to get tin box containing a FBT and a few other components will fix the problem. I do not believe that the actual FBT is faulty, as in some cases the symptoms are intermittent. FBT's usually are not intermittent, and either burn, short out or work ok. Does anybody out there know the "real" info or story on these models?

My experience with these models wasn't the flyback causing the problem, but the voltage multiplier/focus divider. This is usually noticed by a flickering screen, intermittent focus problems and intermittent video. These units are made by Philips for Compaq (Qvision 200) and other companies. The flyback is easy to order from CCS, but I have had a difficult time trying to get the multiplier/focus module. I contacted Philips (which is an expensive 900 call) and was told that they don't have the module, that it is only available from the company the monitor was built for. I then contacted Compaq, they denied being able to provide any parts, that Philips would have to provide the part. Possibly someone else may know who sells this module.

This module is available USED from HULCOTE ELECTRONICS EUROPE LTD. They specialize in new and used monitor parts. I just received a used deflection board assembly from them to replace a badly burned one in a COMPAQ 480. Their e-mail address is Landline is 01234 344206 FAX 01234 269538. Very nice people to deal with.




QUESTION NO. P430-8: I have a couple of Samsung monitors Samtron SC528UXL sold as AST Vision 5L. There is very dark image or no image at all. Flyback seems to be working OK, filament draws about .6 A. It seems to be problem with the crt. Does anyone have similar experience or suggestion ?

It is commonly regarded in the monitor repair circles that these samsung CRTs are not good. They lose emission often. A CRT tester will show if this is the case.




QUESTION NO. P56-6: Pionex VM 1491H lost vertical scan, several resistors burned, need values of R464,R465.

There are two Electrolytic caps in the power supply that cause over voltage which damages the Vertical output circuit. R465 220 ohm; R464 2.2K ohm. Caps that cause the problem are 1 uf and 10 uf near the SMPS transformer. FYI: there are several versions of this circuit board with different numbers for the components.




QUESTION NO. P56-7: I am working a a Compaq 461 14" monitor (ADI SM-5514N). It was not producing any video. I replaced the Zilog IC and I now have video back. The problem is it will not sync on all video modes. It will sync on 1024x768 I or NI but not at 640x480 I or NI.

There are several versions of CPU chip. Be sure you have read the "Rework" instruction sheet to verify the correct modifications have been made.




QUESTION NO. P56-5: I have repaired a CTX1461 monitor, only to find that the original cause of the failure is an intermittant open within the power supply transformer. The failure took out 3 components, the switcher fet, zener, and shunt resistor. All replaced and the unit works. The problem is that under a small amount of vibration a transformer winding opens. Where can I buy the xfrm #47S00-0490? CTX is out of stock and said to call back in 3 weeks. Any ideas?

Most of the problems with this unit are cracked solder joints on the "Daughter" board. This problem is very common with the 1561 & 1461 CTX monitors.




QUESTION NO. P56-4: I am repairing an ADI monitor model SM-5514B. The horizontal drive transistor gets its drive from LA7851. But there is no voltage on its collector. Therefore the monitor is dead apart from PSU. Tracing the print brought me to two devices which appear to supply/control power to transistor. They look like small signal transistors, but I have no idea what they are. They do not measure like transistors at all. Reference numbers are Q806 and Q807. Q806 is marked as NIA4M/K327C Q807 is AIA4M/K325C. If anyone knows what they are or has a circuit diagram to suggest how hor. drive transistor gets its collector supply this help will be appriciated.

Q806 and Q807 are NEC digital switching transistors (AA1A4M = NPN, and AN1A4M = PNP), and will not test out like typical transistors. Before replacing them, first check for the "sync for power" output signal from that little CPU-type board, which goes to Q806, Q807 to switch the B+ for the HOT. If that signal is not there, you are in shutdown, and your problem is with this CPU board. But occasionally those digital transistors do go bad. The following data should allow you to check out these transistors. Both transistors are 50 Vceo, 0.1 Amp, 0.25 Watt, pinout ECB, and have two internal 10K resistors that form a voltage divider network. One resistor goes from the base pin to the base of the transistor, and the other from the base to the emitter pin. This voltage divider on the base increases the voltage needed for driving the transistors, and also creates a 20 Kohm resistance path between the base pin and emitter pin, even on working units. If you DO need new digital transistors, a sub is NTE/ECG 2355 (NPN) or NTE/ECG 2356 (PNP).

That device is a digital switch, ECG 2355. Your problem is not likely with those, the drive signal comes from the CPU board. The CPU is frequently the defective component.




QUESTION NO. P430-2: I have a SGI monitor model number cm2086a3sg. Is this a multi sync monitor?

Both revisions C and D of this monitor are listed as fixed frequency, analog, sync-on-green, not as multisync.




QUESTION NO. P429-3: Vertical deflection failure, need values of R465, R466 on 1992-11-17 Anco Monitor board 1491H/1492H sold with Pionex 486/25.

R465 = 270 ohm and R466 = 10 ohm. Bad power supply regulation can burn these vertical components, so with these two resistors burnt, better also check the values and/or ESR of the following: R392 = 100 or 120 ohm; C411 = 1uF/50V; C611 = 1uF/50V; C612 = 10uF/100V; C731 = 47uF/160V; C741 = 10uF/100V; and check the vertical position adjustment pot (1K ohm pot) for damage.




QUESTION NO. P428-3: I came across a computer monitor I've never heard of before. It's called a "loop monitor". It is non-responsive to incoming video. It has an input that says "signal TTL" which looks like a svga input and a second input "signal analog" that looks like an older cga connector. Any repair data on this monitor or it's real maker?

These Loop monitors were sold in Computer Shopper in the early '90s. They MUST have a special video cable. They will work with the "Sony" type svga 9 pin cables.




QUESTION NO. P428-8: I have a MAC 21 inch monitor with Horz problems. I have replaced the transistor V104 and resistors R113 and R109. The monitor "fired up" for a second and then blew the parts out again. I do not know where to locate: (a) a schematic for the M3502 family (b) special chassis parts Can anyone suggest a cure or source of info for the monitor?

Besides the components you mentioned having replaced, you probably need to replace snubber caps C106 (0.0056 uF/ 2 KV) and C108 (0.011 uF/ 2 KV), connected across V104. These are typically Philips caps, and are usually bad in your situation, especially C108. It is also a good idea to check C121 (10uF/63V), C124 (10uF/63V), and C138 (33uF/16V).




QUESTION NO. P428-1: I have an Nec JC-1539VMA that has an orange power light, no high voltage (it only draws about .05 amps of current), I've checked most of the power supply components but can find no bad parts. Does anyone have any experience with this one?

These units are notorious for having defective IC881 microprocessors, Toshiba TMP87CK42N-4147, which mimic power supply problems when bad. NEI (800-659-3186) or CCS (800-356-1227) may have this IC, but it is pricy.




QUESTION NO. P330-6: I am repairing a CTX 1451 monitor that has burned several parts beyond recognition. I am looking for the values of R119, R112, and ZD101.

I have looked in a CTX 1451 for you and have this info. R119 = 33k 2 Watt R112 = 1K .25W ZD101 ? only found ZD 102 = 18V 1 watt Zener.




QUESTION NO. P417-8: I have a Toshiba 32G90 which won't startup. The power LED blinks on/off about once every second. After awhile, the set will turn on and work fine from then on.

If the cycling on-off gets faster (say over 3-5 min.) look for a 330uF/16V cap near the power xfmr.




QUESTION NO. P325-10: I have an IBM G70 which is completely dead.By probing at the SMPS I can see attempts to start but nothing happens. HOT measures ok.

Check the diode CR210... (can be replaced by BYV29-500). If it's ok, then check CR112, CR122 (can be replaced by 20V zener). If replaced, both diodes must be replaced, and flyback-tranformer must be adjusted . Also check Q101, Q102, R103 and R104.




QUESTION NO. P318-3: I have a Gateway CS1776LE Monitor that went dead. I replaced PS tranny, HOT and Q116, plus many electrolytics just in case. The PS runs ok with all correct voltages.HV comes on and immediately shuts down. Relay RL101 kicks on and HV switches off. Relay drive comes from a daughter board. Does anyone know why it is supplying the command to switch the relay off? How do I fix this?

Adjust xray and see if your monitor will stay on, and if you have a reduced width you need to replace c134 .0075uf @1600v. Also checkc120,c123 and L105.




QUESTION NO. P415-5 : Packard bell 1412sl dead. I have had little luck with p-bells due to the board mtd to the basemaking testing difficult had some that seemed to draw 1/2 power ~20 watts no hv this one dead Common points to check?

Suspect the electrolytic capacitors in the vertical circuit. Probably the cause of the original is failure.




QUESTION NO. P415-6: I have a Viewsonic 5 computer monitor that had vertical collapse. I found a defective IC202 vertical out ic. I replaced the IC now I have a picture with severe vertical foldover.

If this ic you replaced is the vertical amplifier. Then check the electrolitic caps around the Ic . I have had this IC replaced with a different Manufacters product. Some times the spaecs are so close that changing this chip will solve your problem.




QUESTION NO. P311-3: I have several daewoo 17 inch monitors, mod# CMC-1701M2. crt pcb does "electrical dance". The power supply goes crazy (switching} but checks ok. hot ok. All diodes ok. Suspect flyback?

I have encountered the same problem many times. As much as you do not want to hear it the Flyback is the only answer!




QUESTION NO. P48-7: I have a CTX CMS-1461 monitor with a problem. The screen is shifted horizontally and cannot be adjusted to correct position. By shifted Horizontally, I mean that it starts in the center of the CRT and wraps around to finish the image so that the right half of the image is on the left half of the screen and vice-versa. The monitor would not work at all initially. This problem was traced to bad solder joints from a previous ?repair? or attempt to repair. I have since replaced the LA7851, several capacitors and diodes to no effect. I suspect the HOT is fine as aside from being shifted the picture is fine.Anyone have any ideas as to what to look for? Anyone seen this condition before?

I have no personal knowledge of the horozontal shift, however I do recall another tech in our shop having the same or similar symptoms. I believe the solution was an incorrect sub or something related to the horiz. output. If this does not help resubmit question and i will specifically ask him.His trouble was only couple of months ago. I try to review this board at least once a week so would answer fast.




QUESTION NO. P330-9: I am working on a Sony KV20TS20 which has a problem in the Horizontal circuit. The horiz out keeps blowing after about a week. It does not run hot or anything but R605 Keeps opening. So it does have a heavy short in there when it does go. Anyone run across this before?

Replace the horizontal only with original sony part subs will not last.




QUESTION NO. P49-8: J'ai un Packard Bell modèle 2020 qui au bout de 30mm se coupe.Une idée?

This question is the same as P1217-9. Look in the FAQ [In french] Il y a deja une reponse a cette question sous la reference P1217-9 Regarde dans la liste des reponses




QUESTION NO. P326-3: Epson monitor model # MCH-4095E with 9 pin "D" input connector. Monitor is selectable mono (blue or amber). Need to know connector pin assignments and mostly the type of PC video driver card to use. FCC ID #BEJ9QKMCH4095N

Pin assignment for a monochrome 9-pin D connector are:

1, 2: Ground


3, 4, 5: not connected


6: intensity control (contrast)


7: video signal input


8: horizontal sync.


9: vertical sync.


Video monochrome cards usable are:MDA (monochrome display adapter) HGA (Hercules graphics adapter) -Some CGA (Color graphics adapter) and EGA (enhanced graphics adapter) cards that have a switch mono-color can also be used.





QUESTION NO. P48-6: I have a CTX 1451C that has D402 shorted "actually it blew in half and I do not know the part number" its a physically large diode on a heat sink in horz section. I replaced with another large diode just guessing at the value anyway it came up but is drawing about 1.5 amps current and has a loud hum. It also had a pincushion problem which was Q404 "A1015", I was checking parts and turning it on periodically and then d402 shorted again. Does anyone have a fix for this one or at least know the right part number for d402? It looked like 3TH from what I could make out.

Two rectifiers are made that start with "3TH", Toshiba's 3TH41 and 3TH41A, both in 8 mm long by 6 mm dia. packages. These are rated for 1500 V., 3 Amps, and are fast recovery types (<1.5 usec for 3TH41, <1 usec for 3TH41A). Unless your substitute rectifier for D402 met these specifications, that could be one source of your problems.




QUESTION NO. P47-11: I have a Gateway Cs1024NI2 monitor original complaint was display too dark. I found R241 burnt beyond recognition anyone know it's value?

R241 is 20 ohm, 1 Watt. If that one is gone, then you had better also check ZD202 = 20V/1W zener; R325, R335 = 33K ohm; R331 = 91K ohm (must be exact value, no higher); caps C315 and C316. R241 and ZD202 usually blow from excess voltage, often due to one or more of those others being faulty.




QUESTION NO. P310-5: I have a Gateway 2000 15" Vivitron monitor made by Sony (model CPD-15F13). The unit powers up and the green power LED comes on for a few seconds. The power supply sounds like it tries to start up again after a few seconds and then both the amber and green LEDs flash with no video.

I had a similar problem which was resolved by resoldering the middle section on the main board. It seems to be caused by the fixture holding the monitor to the base rubbing against the main board damaging/scratching the joints/print. Apparently this problem is a known design fault.




QUESTION NO. P325-6: I have a Sceptre monitor, model #H566, PN:P51, which will not sync on 640x350 or 640x480. On these modes I get squashed video at the top 1/4 of the screen which resembles a video IC problem. All other modes work fine. I suspect the TDA9103 IC but I would like a second opinion.

Sceptre units often have problems related to bad TDA9103 IC's. One symptom these IC's cause is loss of sync, esp. in the lower modes; another is pincushion. Usually, the IC's are worse when hot, so see if freeze spraying the IC makes a difference. Also, if the AGC memory cap off pin# 25 of TDA9103 is even slightly leaky (0.1 uA), AGC function is not reliable. The AGC re-establishes vert. amplitude after freq. shifts, so you may wish to check that cap (typ. 0.47 uF) for leakiness with a reduced vert. height symptom; replace with a low leakage cap.




QUESTION NO. P35-2: I currently have two ACER Acerview 34T Model 7034T monitors that require Flyback Transformers. The part # on the Flyback is 19.70016.001. I cannot find any reference or cross reference to this flyback. Is there a source for these or a cross reference or substitute?

Call Component Technologies. Their number is 1-888-flyback.




QUESTION NO. P330-8: I have horizontal problem is a Dell Mdl D1727S-HS SVGA monitor. FCC ID: A3LCMH737. High voltage comes up but not measured. The image on the screenis only 2" wide from top of the screen to the bottom. The video is all there inside this two inches, ie; you can read some of the characters. The sides of the image are straight not pinned. The dc power supply voltages were checked and are ok. The vertical shift and size seem to change in the image but the horizontal shift and size doesn't change anything. IC201 (uproc) has horz sync going in and out, also the horz size output from the chip is changing the duty cycle. Horz sync is then fed into a sync processor IC401 a TDA9103. When changing the horz shift or size, nothing changes on the horz sync out pin. The output is a 50% duty cycle square wave that doesn't change at all with shift or size adjusted. The collector of Q407 is 400vp-p. I have checked everything in the horz circuit and have changed the TDA9103 but cannot find the problem.

I had a problem on a 17inch identical to yours. I found that the hot was breaking down. When I pulled the old hot out and compared it to a new one it was very obvious using a curve tracer. I hope that helps.

If I read you correctly, the horiz. output of the TDA9103 (pin 20 or 21) is pinned at its maximal duty cycle (50%) regardless of input. This duty cycle level is controlled by a DC voltage to pin# 2 of the TDA9103. That voltage must lie between 2 and 6 VDC (assuming pin# 5 = 8 VDC) to be legal; 2V gives minimal duty cycle, while 6V gives maximum (50%). Try monitoring the input to pin# 2 and seeing if it is within legal limits, and if this DC control voltage can be varied between these limits. Assuming the TDA9103 is functional, it sounds like that pin is stuck high, and so tracing back from this point should lead to the culprit.




QUESTION NO. P323-5: I moved into monitor repair Jan 1st and have pretty good luck at getting monitors repaired with most video, horizontal, power supply, or vertical problems. I have been getting a few monitors in the shop that have problems when changing modes though. These sets are giving me fits and really limiting my production. I have bought books, tapes and software on monitor repair. Still no solutions. Since this seems to be generic to all makes there must be some tips someone can give me in troubleshooting these sets. The symptoms typically are as follows: VGA mode will sync and will be of the correct size. 800/600 will/will not sync, or is off center and squeezed in a little horizontally. 1024/768 will/will not, sync or may/may not be centered or sized correctly. Most printed materials and tapes on monitor repair give examples that are pretty simple problems and no examples of odd or tough dog problems.

One thing I find in the area where you're looking, the line sync. In the case of vga the line (horizontal) oscillator runs at a different frequency than in svga (higher). Think of monitors like tv's with the rf and if ripped out. They are a world wide standard which is useful. Your fault sounds like it may be in the sync or osc. timing circuit. I cannot help anymore than that, but I know it fooled me when I first saw it. Think of it like a dual standard tv. Ie 625 / 525 lines.

You may not be aware that all vga monitors will sync in on your basic 640x480 but not all are created equal. A lot of monitors are nothing more than basic vga,not supervga. A good indicator is if you see adjustment controls inside that give you individual controls on different freq ie..vheight and hpos.that allows you to adjust all your screens to be centerd when switching from one mode to the other. A lot of times you will find that you can get pictures on some monitors that are not designed for it but the syncs will be off. I hope that helps.




QUESTION NO. P330-7: I am trying to find any info. on a 27 inch "data grade" monitor made by a now defunct company named "frox". It was originally part of an elaborate and very expensive tv/cd/a/v system for home entertainment back in the 80's. To the best of my knowledge they went out of the business.

Check FCC Data for mfgr info. It should have FCC ID number located on unit, prob near model number tag.




I have seen monitors with the Weltrend Chips having thermal problems. This seems to be a pretty common problem with Weltrend WT80XX chips, especially in monitors that have those chips mounted up under the CRT. With these chips mounted there it is hard to get a sufficient amount of air flow to cool them and sooner or later they seem to break down and become thermal time-outs for sync. The SuperCom is just such a monitor, and the AOC is a close follower. There are probably more than I realize that have this inherent problem.

Recently I bought some monitors just to have as loaners. Among these was a SuperCom ST1496 (popular with this problem). I decided that Weltrend should be putting heatsinks on these chips and wanted to see the effect a heatsink would have. I cut a piece of 22ga aluminum into a rectangle approximally 1.5" X 2.375", cut fins into it on both sides, (on the side close to the CRT these were shorter than the ones on the side toward the back of the board), and used small needle-nose pliars to twist the fins to a 45 degree angle. The center of the heatsink I left wide enough to just fit on the surface of the chip, making sure the fins would not be too close to the pins. Then I used JB Weld and mixed enough to cement the heatsink to the WT8042.


I have left the monitor on for as much as two and one half days solid with no loss of sync, even after this chip had already been weakened by the heat and was loosing it's sync after about an hour. I would have either installed a new chip or attempted this repair only after discussing it with the owner had this not been mymonitor, but I was curious and had nothing to loose.


I might even try mounting a heatsink using this technique on a new chip sometime. JBWeld to those who haven't used it is an epoxy base filled with steelpowder. Maybe they make an aluminum filled epoxy (more conductive).





QUESTION NO. P32-7: I have an Acer View 44, (virtually identical to the View 34T) that has a strange problem...Periodically, the picture fades out to black. Hitting the monitor on the side sometimes brings it back. Sometimes the picture looks washed out and overdriven. I have tried touching some of the most suspect solder points, but it would help if I had a starting point.

Check TRC heater voltage (6,3 V., pins 3-4 of TRC socket counting counterclockwise) when picture goes off; if there's no voltage but it appears when picture comes back, look for bad solder joints tracing the circuit backwards to the power supply. Usually, the 6,3 V. tension comes from a single diode-electrolitic cap circuit at the secondary of the power supply transformer.




QUESTION NO. P319-5: I have several Compaq model 420 VGA monitors with no vertical sync. HV and signal are good (you can see the squished text on the horizontal line). I've heard is was a major problem back in early 90's with the 420 models. Has anybody else had the same symptoms? What IC's, caps, etc. should I be checking?

Yes the Compaq 420 had this problem quiet often. I have fixed several dozen of them with this same symptom. You usually have to replace one IC and one resistor to fix the problem. IC-202 (TDA 1170S) and R-215 (8.2 ohm resistor). R-215 will probably be burnt. In a small percentage of them you will also need to replace R320 and the diode at D306. These are both near the flyback transformer. The resistor will read open and the diode will read as shorted.




QUESTION NO. P36-9: Does anyone know what test equipment is nessasary to program the newer type monitors to set crt tracking for greyscale on monitors without individual potentiometers on the crt video board and where to purchase it?

The only monitors I have seen without internal color controls have digital controls for color drive. These controls are accessed through the main menu on the front panel.




QUESTION NO. P314-3: I am working on a Samsung SC-428PTL with the following problem: There is pincushion and the horizontal size is too big. It cannot be adjusted with the potentiometers for pincushion and horizontal size. Does anyone know the solution for this problem?

Suspect possible bad connections in deflection circuits, esp near the capacitors in the horiz. Also check any PCC correction active devices for proper bias voltages and signals. Shorted or open diodes in damper circuits for pcc also may be a suspect. Leaky or open ringing capacitors in yoke supply [ horiz and vert] can cause pcc. Excesive width probable incorrect supply voltage or open ringing cap in horiz circuit. Coupled with the PCC problem I would suspect open or leaky components.




QUESTION NO. P311-4: I have an AURORAVISON SM583 15" monitor where the image shudders everytime the case is lightly tapped.Read somewhere that this is a common problem with this model.

Check crt board/and or main board for loose solder connections.




QUESTION NO. P226-8: I have a Gateway CS1572FS the original problem was Q301(HV80) and IC301(UC3842A) was blown. Electrolytics in SMPS circuit checked O.K. Q303(MCR100-6) was replaced with ECG5405. There is a whine from the SMPS transformer as if it is not starting up.No power elsewhere in monitor. Checked R331(91k) O.K. I don't have a schematic for this monitor but I checked the data sheet for the UC3842A and the Osc. looked around 20KHz.

This is a common problem with these monitors. It is from the 180V supply being too high, due to a feedback resistor going up in value, R331. Should be about 91K, unsolder one lead and measure it, if it's much higher than that, replace it. Then adjust the pot associated with it, VR303, so that the supply you measure across C321 is about 185V. Also Check R153, F301, Q301, ZD307, IC301, D307, A106, C116.




QUESTION NO. P29-8: I have a Dell D1528 Monitor That flashes the Green to Amber LED when powered up, however it justs keeps doing that and never powers up the screen

Check for a shorted HOT. Something is shorting the B+.




QUESTION NO. P36-6: Tengo un monitor IBM mod 6322 con el siguiente problema, no hay deflexion vertical esto ocurrio despues de averiarse el teclado e verificado el circuito de vertical y en una de las patas del tda 8351 hay 45v ¿es normal? ¿ideas?

I have a monitor IBM mod 6322 with no vertical deflection due to damage to the keyboard. I checked the vertical circuit and in one of the legs of tda 8351 there is 45v. Is this normal? Ideas?

If you have TDA8351, a 9-pin device, then pin # 6 can have up to 50-60 Volts in normal operation, and 45 Volts is a typical value. Pin 6 is the input for the supply to the flyback switch. If instead you have TDA8351A, a 13-pin device, this input is at pin # 8. For more information on TDA8351, download the datasheet from

Si usted tiene TDA8351, un dispositivo de los 9-contactos, después un contacto # 6 pueden tener hasta 50-60 voltios en la operación normal, y 45 voltios son un valor típico. El contacto 6 es la entrada de información para la fuente al interruptor del tiempo de retorno. Si en lugar de otro usted tiene TDA8351A, un dispositivo del 13-contacto, esta entrada de información está en el contacto # 8. Para más información sobre TDA8351, descargue el datasheet de




QUESTION NO. P36-3: My tech is currently analyzing a problem with an NEC XE15. When I turn it on I get the orange (standby mode) power light. It does not change to green when video is applied. There is a high pitched squeal which increses in pitch and intensity as you increase the brightness controll. The horizontal output transitor tests as shorted when the flyback is connected but when it is disconnected it tests good. He suspects a bad flyback but is not sure.

Suspect the damper diode[s], and any other components around the hot. Try a flyback tester [ringer] if available. The diodes within the flyback [tripler] also may be defective or shorted truns within the flyback. Check external components first before condemming the fbt. Look for any signs of perforation thru the casing of the flyback.




QUESTION NO. P36-2: I have 3 samsung cvp4237p monitors with the exact same snag, no picture, no hv at anode, and a very good purple glow in the crt neck. Disconecting the crt plug and hv comes up. I believe there is a short in the neck and want to confirm but I need a pin out of the crt for this model. Can someone provide a pinout?

I bet you will find a crack in the neck under the yokes. Sounds like poor quality tubes or over-tightened yoke hardware may be to blame.




QUESTION NO. P219-6: I have 3 monitors model IBM 9518-001, with problems in the vertical, there is no stable image. Any idea?

The 95xx series monitors are XGA variety. Which translates to a special type needing a different drive signal, otherthan a std vga signal. Symptoms are loss of vertical and horiz sync.




QUESTION NO. P220-2: I have a monitor model IBM 8512-001,with problems in the vertical, there is no stable image. Change the resistances of adjustment, an I didn´t obtain results. Any idea?

Verify that pin 14(Vert.Sig) from the cable end position to the chassis is not open. These IBM cables have been known to open very easily. Generaly kinks at the cabinet input area are common.

Check the capacitor that is across the vertical yoke pins on the mainboard.




SuperCom ST1496 Monitor looses horizontal and vertical sync after warmup of about 10-20 minutes..

Replace Weltrend WT8052 (IC-U505) Left/Front of mother board.Using a coolant after unit goes out of sync will confirm this repair




QUESTION NO. P219-2: I have burned components on power supply board in monitor AOC model:cm-335. Can someone tell me the value of ZD904?

ZD904 is 6v/1watt. You can use ECG 5070A.




QUESTION NO. P210-4: I have a Dell VI1428U made by Lite-On, many power supply caps were bad and replaced, Power and high voltage is present but still have no video and monitor is squealing. I have about 10 of these models. Need suggestions.

Check the values of R436 resistance and R437 is located near the fly-back. They should be 1M ohm..




QUESTION NO. P213-10: I have got a Tatung CM14SBS monitor. The picture does not fill the 14 inch screen fully.If strecthed to fill screen picture not symetrical. The picture looks good with 1/2 inch black border around it.Is this a design flaw with this monitor?Tried adjusting B+ and internal horizontal width pot.

You are correct this monitor was designed that way. You will have about a 1/2 inch border at both side.




QUESTION NO. P25-1: I am working on a Packard Bell monitor Mod# 1402S. It originally had no vertical deflection. I replaced vertical IC TDA4866, and R612 1ohm, half-watt, which was burned. I hooked it up, and all was well, except for the tint. I disconnected the monitor from power and deguassed the crt face as I would a TV. Reinstalled it in the case. Hooked back up for a final check. Now I have no raster, and an arcing noise. I viewed the chassis with no ambient light, and could not see the arcing. I had 8KV on CRT anode lead before, and now I have zero. What have I done wrong?

Check capacitor C812 47uf 160 volts. Also cut the nylon tie holding the high voltage lead going to the CRT circuit board and inspect the wire for breaks in the insulation. I also found three bad capacitors on the CRT board on the 1402s that I was working on. I do not remember the numbers, but they were the small caps about 1uf at 100 volts. Two of them were yellow in color.




QUESTION NO. P127-1: Looking for help on NEC Model JC-1433VMA with no video symptom. Powers on but no video.

Key items were missing in your question. Does the HV cycle on and stay on? This is confirmed by either HV Voltage probe or by hearing the crackle. If HV is present is the filament lit? Either or both would cause no video to appear.




QUESTION NO. P25-5: I have a CTX monitor model #CPS1760 LR. Comes up with video very slow, checked for bad caps & fly-back; check OK. Is there a series of caps that go bad & where should I check?

Replace electrolytic caps in secondary psu. They are next to the diodes in the secondary supply.




QUESTION NO. P120-1: I have a 14" monitor with EMC tube, and the brightness is very high (white screen). I am already checked the pot, and is ok. In the CRT board, I changed the LM1203 and there is no effect. I already checked for bad resistors, but they seem to be ok. I checked de capacitors and it seems to be ok. Is the problem in the CRT board?





QUESTION NO. P22-3: I have a Supercom SK1592 monitor in the shop which suffers from excessive width and pincushion. Width and pincushion controls have barely noticable effect. I have yet to locate the defective part. Has anyone else dealt with this model and/or problem?

Check the deflection yoke for shorts




QUESTION NO. P24-3: I have several IBM 8515-001 monitors all of which have a hole in the lopt. After replacing the lopt and checking the hot the unit starts and then goes into protection immediately and switches off, even the led goes out. It is not a short on the secondary of the psu. I have tested.the new lopt works in a working unit. The vertical ic appears to be ok.

Check for a bad capacitor to the rear of the board, near the lopt.




QUESTION NO. P15-3: I have a Mitsubishi monitor model# C-6922AGK the monitor works fine while in windows 95 (640X480) but if I shell out to DOS the monitor scrolls vertically as if the sync is missing. Does anyone have a fix for me?

Using Device Manager, Remove, then re-install your video drivers. It sounds crazy but it worked for us!




QUESTION NO. P114-3: I am working on a tosh CF3048 which seems to have a pincushion type problem. The raster covers the screen but the video looks bowed in on the sides. Also there are slight vert retrace lines at the top which I think is a separate problem. Anyone had a similiar problem with this set? Or can lead me in the right direction?

Possible causes are corroded C305 (near vert IC) & C301 (near Center of main PCB). Both caps are Red & must be replaced w/ 2.2uF/50V - 105c high temp caps.




QUESTION NO. P126-9: I have a Orchestra French Horn 15" that has a pin-cushion problem. The sides of the picture in the display bow in. The pin-cushion adjustment pot inside will not adjust the problem. It seems to be something other than the pot. I have adjusted that pot in the past with results. Have any ideas?

This monitor has probably FCC KD-1500 or KD-3500 made by KDS. If so, replace cap c636, 3.3uf/250v. Try to relocate it as far as possible from heat sink. It will solve your problem with pincusion.




QUESTION NO. P23-3: I have an IBM 9517-001 monitor with a sync problem. It will sync at 640 x 480, but will not sync at any other frequency. The display appears to be shifted to the left, and when entering Win95, display goes completely off, and appears to be at the top of the screen. In other responses on this service, similar questions were answered the monitor being an XGA and not capable of VGA and SVGA. Is this monitor an XGA as well?

BM monitors with model numbers beginning with "95" are XGA monitors. These monitors are generally not compatible with VGA/SVGA systems.




QUESTION NO. P122-7: I have a Gateway CrystalScan 1776 LE monitor in for repair. Gateway has looked at this monitor, and has been unable to solve the problem. With the brightness at normal to high levels, there are several light bands that can been seen, going from top to bottom, at the left side of the screen, whose total width covers approximately 3 to 4 inches of the left side of the screen.

I would check the cap that are filter for the video ic lm1203 or similar. I had some that had bad esr. If you do not have a esr cap meter jump a good one across it. Sometimes the cap check good on cap meter but esr is no good. I have also seen bad crt doing the same problem it look like a image being inserted on top of video.




QUESTION NO. P129-8: I have a CTX monitor model# CPS1760 LR. It has a vertical collapse. I have changed the vertical IC7838 & checked for bad transistors.

One common problem giving no vertical deflection in this unit is bad solder joints on the pincushion correction PC board, near the top of the yoke. Check carefully and resolder: often very hard to spot the bad joints.




QUESTION NO. P15-4: I have multiple DX17F's which routinely fry the HOT. I have replaced all the normal parts HOT, C123, C120, L105, R177.D116, Q116. They all seem to work ok then but have squashed text on very right side. Does any have any ideas. Does anyone have the recommended proceedure for setting the current though the HOT?

Check C134 and C908.




QUESTION NO. P122-6: I have a gateway 200 (Vivitron) 17" monitor that invariably goes into power save mode on startup. If I push the reset button I get the message 'out of scan range'. +12vdc drops to 1.6vdc.

"Out of scan range"indicates a disconnected data cable, more accurately no signal to the monitor. The power save feature powers down most of the unit if it doesn't detect a sync signal, assuming your pc is off, inactive, etc. Check cable continuity closely. Somehow unit the is losing signal.




QUESTION NO. P119-10: Does anyone know how to open the case of a Apple MultipleScan 15 Display?

There are two small holes at top of the monitor. Insert a small screwdrive into the holes and push tab down while pulling apart.




QUESTION NO. P123-3: I have a Packard Bell 1402S monitor that has a burnt resistor that I cannot find the value for. The location is R454. Does anybody know the value of this resistor?

I measured the value of resistor R454 in a Packard Bell model 1402s as 222.7K ohms. The color code looks like red, red, black, orange. The body of the resistor is green.




QUESTION NO. P120-7: I investigated a color purity problem and determined that portions of the office furniture were magnetized, especially near the seams. I assume spot welding does this. I used a fluxgate dc meter and found 1-3 gauss dc near the shelves and drawers. The user does not believe this is possible. Am I correct, is it possible that office furniture can be sufficiently magnetized to cause color purity problems, and are there any references on this phenomenon? If I am correct I intend to attempt to degauss the affected metal pieces of furniture.

Absolutely !! I have a customer in Lake Orion, Michigan who has a steel beam in his residence magnetized. The house has been hit by lightning. There are only two physical places in the house he can have a colour tv with a half-way desent picture. The probality of the steel office furniture being magnatized is very possible. The companies who manufacture these items usually degauss them before shipping.




QUESTION NO. P120-6: I have a Sony CPD-1425 with a "no power" symptom. The start up cap at IC1 is not charging to 16v to start the PWM chip. I have changed the start-up cap C14 without the problem being resolved. I notice that when the main PCB is flexed some; C14 will charge to a slightly higher voltage and occasionally cause the PWM chip to start. Has anyone encountered a similar fault, Or have any other ideas?

I actually solved this problem; I over looked the obvious as we all tend to do from time to time. The problem was solved by replacing the DPDT Power switch. On one contact the resistance was around 600Ohms when closed, and the other close to zero Ohms as it should have been. Found replacement (exact replacement) through MCM Electronics. Dont let this one catch you!




QUESTION NO. P115-1: Have a Sony KV-32XBR70 TV that has vertical jumping of the horiz. scan lines. May be aprox. 10 lines jumping or spreading apart at a random position and rate. Only seen thru out top half of picture. Also I notice a audible noise that seems to be in step with the random jumping of the scan lines. I suspect the noise may be coming from the yoke.Is the deflection yoke bad?

No. Probable breakdown of one of the active devices in vertical deflection. May be cap breaking down, also check components in PCC circuit.




QUESTION NO. P116-10: Goldstar GHV-1280M VCR. Need voltage regulator information, ie part number, replacement type, etc. The suspect IC is D101. The power supply works in European voltage, but not 110 vac. All voltages are low, and I believe the regulator cannot handle it.

European Voltage? 220, 208, or what? That unit may be set for 220 input. Plugging into 110 will cause all voltages to read low and may cause some items to overheat. Findout what you are working on, get the proper matching transformer for the AC supply, then troubleshoot.




QUESTION NO. P116-5: I have several NEC 2A monitors (JC 1403HMA) with similar symptoms. The display is out of focus when turned on. The picture focus improves the longer the monitor is on. One of the monitors appears to have healed itself, meaning the focus and brightness are good at all times, however, when the computer is turned off the raster is visible (not blanked) and a few of the retrace lines are brighter than others.

ANSWER 1: How old? Possible crt, suspect crt socket for high resistance path from focus to grnd. Other things may be failure in Focus supply from FBT or focus/screen control assembly.

ANSWER 2: Sounds like it is temperature related, possibly a bad cap. Try using a hair dryer to heat up components and watch for inprovement.




QUESTION NO. P116-3: Working from your advice, without a schematic, on a dead CTX-1561. Swapped out R114, R111, R112, R113, ZD101, ZD102, 2SK955, and 2SC3886A. Good picture for 90 seconds, then horizontal raster collapses and blows fuse. I would appreciate any help, and would like to know the values of D101 and D108.

Possible flyback may be breaking down. Use a ring tester if you have one. Check yoke for possible worn coating on coils esp those in contact woth dag coating of crt. Does FBT become hot before fuse blows, does yoke become hot? Doubtless the Hout fries but overload somewhere in def sys is problem. May even be leaky cap in hz out ckt.




QUESTION NO. P116-1: I have a JVC 860 & 870 both with the same problem. When plugged in the relays click but the machine will not power up. On the 860 I have changed c6,q1,q2 and c9. On the 870 I changed just q1 and the bridge rectifier as it was blowing fuses at first. What is interesting is that if I press the top of c9 with my finger (it sounds as if its leaking) the machine will power up. I have changed this cap in both machines though and it made no difference. at this point.

Pressing physically may be flexing the pcb beneath the components or components may be mechanically damaged. Check with a good magnifier for cracked foils or pcb. Also check the solder connection for ring cracks or dirty connections, remove components, clean foils, and reinstall. Keep looking for the not too oblivious cure.




QUESTION NO. P113-4: I need to know a value of resistor 409 of DAEWOO monitor, model CMC-1501BA1.

The value is 120 Ohm, 1/2 Watt.




QUESTION NO. P113-8: I am working on a IBM model 5154 VGA, no raster, no green power LED. Before total failure it was having trouble displaying the first couple of characters on left hand side of the raster.The switching PSU is a modular plug in. I've pulled the horz transistor, it checks OK and does not solve the problem. Have replaced the main IC in the PSU, a SG 3542 switch mode control IC, and this does not solve problem either. Input caps and rectifiers SEEM to perform OK and produce a good 300 v D.C. One clue is the supply to the IC which is usually shown as 28 v D.C. in the data sheet is made from what appears to be some sort of complex boot strap circuit whose source is the big output transformer. Am I chasing my tail on this one ?

This sounds like a classic P.S. failure. Other P.S. that I've repaired had low valued caps in the current sensing curcit. I recall there were 3 electrolitics 10uf, 1uf. & 47uf(not sure). All were grouped together at the top of the board. I assume you have checked the MJE13005's for countinuty.




QUESTION NO. P19-2: IBM - 8514 monitor Diag - dead, fuse is okay. Any help?

Other symptoms would be helpful. As unsual noises squeals, humming. etc.Any LED indications. Two distinct problems come to mind. One is open/shorted HOT. The other is shorted low voltage cap on the video board, something like 100uf @50vdc.




QUESTION NO. P1226-3: Can anyone tell me where to get the pin out for the data cable of an Emerson monitor. I think that this cable is all that is wrong with the monitor. It has a mitsubishi crt in it. Other than that i have no info on it except that it is a 14" svga. No model # is visible.

Computer Component Sources in NY. They have a complete line of replacement cables. Voice 800-356-1227 Fax 800-926-2062 International 516-496-8780.




QUESTION NO. P113-7: I have a Toshiba cf2010j with a vertical deflection and linearity problem. The bottom half of the screen is black and the top has some foldover. I have replaced the signal processing ic and the vertical output chip to no avail. I have also substituted a good yoke with no repair. Any ideas?

Check any diodes and caps connected to the vertical def ckts. Also confirm correct voltages at vert out device pins. I suspect you will find a cap that has opened or one of the bias voltages is not right.




QUESTION NO. P19-8: I am looking for the pin-out assignments for a Commodore 1902A monitor, particularly the 6 pin din socket for the composite video.

Pin identies as follows looking at plug end.

Pin 7 & 8 no connection

Pin 6 Color out. (Chroma sig out)

Pin 5 Audio in.

Pin 4 Video out. (Composite Sig out)

Pin 3 Audio out.

Pin 2 Ground

Pin 1 Lum/Sync. ( Luminance/sync out)

8 7

3 6 1 Plug output from C64

5 4 back of unit.





QUESTION NO. P1222-4: U.S. logic model MM-50,FCC#hsutrldh-1570,mode select schematic.traced h/v sync lines from input cable to an ic203(74hc14n).replaced,no help.traces also lead to ic401(tda9103)suspect this one.only mode ok is 640x480 and 640x350.all others only display the top third of display,with lines running thru, like a vertical distortion.

Does freeze-spraying the TDA9103 affect the symptom? If so, refer to the answer for Question No. P1218-2 on monitor repair.




QUESTION NO. P1218-5: I have a Gateway 2000 DX17F monitor that keeps smoking R177 (1 ohm 2 watt) . I have replaced R177,Q116,C120,C123 and checked all my solder connections. R177 smokes with the data cable in and out.

Besides the components you replaced, there are other problem components in these units. See for further information.




QUESTION NO. P1211-2: I have an IBM model 9518-001 VGA monitor , on boot up the vertical sync is out and a loud squeal when windows starts the colors are blurred, as soon as program manager loads every thing is normal. Does anyone know what this may be?

IBM 9518 is a XGA monitor. It will not work with VGA or SVGA mode.




QUESTION NO. P1211-8: I have a CTX CVP 5468NI, missing the resistor #303. Can anyone tell me the value?.

The resistor R303 is 270K Ohm Red Violet Yellow




QUESTION NO. P129-1: I am working on a NEC / multisync (3DS) M# JC-1404. The video is fine except there are 2 vertical blue bars about 1 1/4" wide on the right side of the display separated by about1 inch. I replaced the 51387 IC with no difference. I also replaced the 3 1Uf 160 volt capacitors as they were reading low. Anyone come across this problem?

Look at question/answer #P1210-8. The problem and solution are what you need. Replace all 3 caps 2.2uf @50vdc off the video processor.




QUESTION NO. P121-10: Princeton multi scan monitor M# eo15 FCC# evokd-1510 Factory # gs 04 Unit has no picture, have tried adjusting brightness to no avail. Has high voltage.

Closely inspect the video board on the tube socket. Look for break in the 12v line to the video chip. These are notorious for breaking. Also look for cold solder joints on the tube socket.




QUESTION NO. P1218-8: Gateway cs 1776le(17",front panel backlit lcd display model,fcc#iawmx17f) shorted yoke drive HOT 2sc4924.replaced with generac part,3.9 ohm 2 watt feeding b+ to it open,replaced.Now a pincusion preblem,can't adjust with rear p.cush.control pot. this pin cush. problem was not there before the HOT type critical? what other parts are likely? Did I "inject"the new problem? Since pincusion is a function of the yoke circuitry, where do I go now?

I located two shorted transistors,"Q909" and "Q506", both 2sd799, darlington power transistors, one on heat sink, and the other stand-alone.




QUESTION NO. P1121-6: I have a Princeton Grapic 15" Multi sync E015 The display is very dim. What could cause this problem?

Check the filament/heater voltage, it should be around 6.3 volt. If it is too low, check the power supply capacitor.




QUESTION NO. P121-4: I have never manage to repair a monitor which has a smearing problem.I have seen monitors with of various brands with a smearing problem either on the right side or on both sides.Several times I have changed the electrolytics on the video board without any success.

The smear on the right side usually is a bad tube problem. Some time it can be fixed by reactivating the tube, but you must have the tool, check SENCORE home page.




QUESTION NO. P1218-2: I have two Polarius monitors (model# 4AL-N).Both are new and the company that sold them no longer exists.They go out of sync after running continuously for 30hrs.They will run forever with cover off. By heating and cooling sync processor (TDA9103) I can simulate the problem. Anyone know of a fix for this one

A number of these ics (TDA9103) made by SG Thomson proved to be defective. Change the ic and in order to completely solve the problem cut a piece of copper shield a little bigger than the ic and glue it on the IC.Then solder this shield to a ground point or pin 19 of the ic.




QUESTION NO. P1218-4: I have a number of KDS-1700V (Korea Data Systems) Monitors that appear to "blow up" for no reason. The problem is Q414 goes short for no apparent reason. This damages Q416 and T401. This can also blow up the power supply. This appears to be a design problem. Can anyone recommend a fix ???. By replacing the above parts (and repairing the power supply) this can last for between 1-2 days and 6-8 weeks. I currently have 40+

monitors with the same problem.

Re-Work Procedure For: KD1700v,Orchestra Tuba2, Princeton Graphics Ultra17 Plus


1. Unpack monitor box, remove packing foam, and plastic bag.


2. Remove back cover and base.


3. Remove top and metal cover.


4. Remove bottom metal chassis and main board metal frame.


5. Pull out main board and disassemble main board from all the metal frames.


6. Change T401 (H. Drive Transformer) P/N KDS2036 to a KDS2036A.


7. Remove the black substrate HIC401,R444,Q413,R460 and BC401.


8. Change HIC402-PT1 to a PT1A. (use adapter board)


9. Add resistors C.F.R. 100K ohm* W on PCB pattern-side of R920.


10. Install 3 jumpers size 2 each 6.5" and 1 each 8.5".


11. Pin #2 of expansion board to R420/J464.


12. Pin #7 of expansion board to Q416/BC401.


13. Q413/collector (on mainboard) to T403/R416.


14. Replace R460 from 51 ohms 1/4w to 32 ohms 1/4w on pcb.


15. Mount the new expansion board in location HIC401. Make sure pin #1 is to Pin #1 (have option board component side facing component side.


16. Install R920 100K ohms 1/4w in parallel on the solder side.


17. Fix each jumper by jam-melt,so they do not move. (Make sure each jumper wire is clear of screws when it is installed)


18. Adjust VR901 to 26kv using a high voltage probe.


19. Adjust brightness and focus.


20. Re-Assemble monitor and mark with a blue dot on the product label near the serial number.


TIP: No video


Solution: Check to see if ZD402 is installed, if not then add add a 1K ohm resister in it's place.


TIP: Video Jitter


Solution: Add a ferrite bead at J402 (use the same one removed from location BC401.


PS: Make sure the screws do not penetrate the jumper wire (pin #7) when attaching the back plate on thr pcb.


One of the problems with these monitors is that some svga video cards, when they change modes, put out a very fast rise time spike on the horzontal line and it kills the horizontal output transistor MJM16212. This can be stopped by opening the horizontal sync lead from the monitors video input db-15 connector and inserting a 3/8 ferrite bead in series with this line. This should stop this very fast rise time spike from destroying the horizontal output transistor.





QUESTION NO. P1217-9: I have 3 Packard bell monitors model 2020. They come up run for a few hours then just shut down. The led on the front changes from green to yellow. just turning off the monitor and right back on it comes up runs for a few hours. Any ideas?

There is a common problem with 2020's (same as PB 1512SL): arcing from the CRT takes out any or all of 3 nearby IC's: IC701, IC702, IC703. The most likely culprit with these symptoms is the IC703 EEprom, usually a 93C56 or 93LC56, especially if holding down the 'Select' button replaces the on/off symptom with an out-of-sync condition, but more than one chip can be zapped. Program a new EEprom from a known good chip, or get a preprogrammed IC from

an outfit like LJ Enterprises (800-627-8755). Note: the problem can recur, unless the chips are shielded from further arcing damage using a strip of metal connected to ground.




QUESTION NO. P1117-4: We have many Gateway 2000 model CrystalScan 1024Ni. The problem is that the image jumps horizontally, and the picture is unstable. Only when the horizontal size control is set to expand the image at minimun, the image turns stable.

From another tech: I got a couple of these monitors in for repair also never found the problem but I definitly know that the problem is not on the main board as I changed it with a good working one.

The jumping horizontally on the gateway 1024ni turned out to be an intermittant front panel control. Disconnect horizontal cener potentiometer and substitute a similar one as test.




QUESTION NO. P1210-8: I am working on a NEC Multi sync 3DS M#JC1404HMA-2 14" monitor. On the right side of the monitor are 2 blue bars about 1 1/4 inch wide running vertically with a spacing of about 3/4 inch. I replaced the 1 Ufd caps on the video board and the M51387 IC with no change.

Check the 3 2.2uf 50v ccaps below your 51387 color processor.




QUESTION NO. P122-2: Several times I have tried to repair monitors which would change display sizecontinously (increasing and decreasing size in all directions at about 2mm).All the voltages at SMPS output seem to be ripple free. B+ is ripple free too.Also nothing seems to be peculiar at CRT pins, either G1 or G2 or color cathodes.Any ideas?

The problem you are describing sounds like high voltage regulation problems. The easiest way to tell is by changing from a black raster to a white raster. If the size changes quite noticeably or jumps alot then you have a regulation problem. The first thing to do is check your high voltage while changing the raster from black to white. If the HV varies by a large margin, then you have a flyback problem. If it doesn't, check the voltage at the collector of the HOT while varying the raster again. If the voltage changes alot then check your B+ line. Typically what goes out in this case is a capacitor(typically 100uf-350v or so) or the B+ regulator. Hope this helps.




QUESTION NO. P1210-9: We have three Apple monitors, “Color Plus 14” Display”, model number M1787, FCC ID: BEJCA453 and made by Goldstar. The common problem is that the display is too wide. There is no external adjustment and the internal H-SIZE pot. has next to no effect. Of course I have no schematics nor know where to get one, so I hope someone can help me by telling me what things to check and/or how to obtain a schematic. One curious correlation is that of the seven of this model that we have, these three are also the only ones without screen savers running.

ANSWER 1: I don't know the specific model but most probably its a faulty transistor.If you check the H-size pot you will see that two legs are connected to ground .Follow the third leg and will lead you to a transistor .This is the most probable fault.

ANSWER 2: Check for a 10uf 160v near the flyback this will cause it to be too wide.

ANSWER 3: Try C721, 47uF @ 100V. It's just to the front of the flyback xformer shield/heat-sink. I think the component is under-engineered: it's pretty small for those values.




QUESTION NO. P123-2: I have a Digital SVGA monitor, model# PC7XV-DE. I am unable to get the colors adjusted correctly. The only way I can get white is if I turn up the green drive all the way, and turn down the red and blue drives all the way. I tested the crt on a Sencore CRT Analyzer, and it tested ok. I am unable to locate the bad component. Does anyone have any suggestions?

Check all electrolytic capacitors on the crt board w/capacitor tester. Scrape glue from component side of crt board (it becomes conductive as it darkens with age). Check for open or increased value resistor in green circuit. Resolder video output transistors.




QUESTION NO. P128-3: I am trying to repair a Samsung 14" monitor CPV4237P The problem is that the video is real faint and can only be seen if it is dark in the room. The HOT seems to be ok and the secondary supply voltages are 151V, 93V, 23.9V, 7.2V, and 6.1V to the heaters. The voltages on the 2 test points near the flyback are 150V, and 86V B+FBT, are these correct or do I have a bad CRT?

The problem you are describing is definitely a bad picture tube. Very common with these models.




QUESTION NO. P1121-9: I have 2 Peri Max SVGA units with same problem. Dim video, brightness and contrast controls do have an effect but at max still dim. I replaced the LM1203N and some high esr caps on neck board no effect.

If you've replaced LM1203N, try going to the National Semiconductor Homepage at there you can download the datasheet for the LM1203N video amp. There is a schematic of a "typical application". Sounds like you have a problem in one of the clamp circuits that control brightness, etc. From the datasheet you should be able tofigure this out.

I have seen a few of these with this symptom. Try shorting pins 12 and 13 on the LM1203n this will be full contrast. If the screen does not brighten up to normal you probably have a bad CRT. I have replaced a few.




QUESTION NO. P1126-1: Gateway Monitor CS1572fs - Screen is wavy -clear but wavy - and unit whines.

B+ is high. Check for open resistor R329 91K 1W. Adjust VR303 for 180V.




QUESTION NO. P123-3: I have burned components on power supply board in monitor AOC model:cm-335. Can someone tell me the value of resistors R937,R927,R941 & diodes D942 , ZD951?

R937=820ohms, R927=1Kohm, R941=270ohm, D942=ECG915, ZD951=6volt.




QUESTION NO. P122-8: Could someone please tell me the value of R105 in a CTX 1451C monitor?

R105 is a 91K @5% 1/8w.




QUESTION NO. P1112-7: A CTX CPS1760 LR has lost it's horizontal size adjustment. The screen is barrelled at the sides (squeezed in the center). All three other screen adjustments work fine. What components should I be looking at?

Look for blown components in pincushion correction circuits. May be active or passive devices. Suspect electrolytic capacitor.