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From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Newsgroups: rec.radio.amateur.misc
Subject: TS520 service notes
Keywords: troubleshoot
Message-ID: <1991Nov24.170347.29597@cbfsb.att.com>
Date: 24 Nov 91 17:03:47 GMT
Sender: news@cbfsb.att.com
Organization: AT&T Bell Laboratories
Lines: 137


copied from packet:
 Msg# TSF  Size #Rd  Date  Time From   MsgID        To
 8166 BF   4244   0 24-Nov 0152 KD2EJ  27230_WB2QJA ALL@ALLBBS ()
Service notes on TS-520                             10-21-77

TRANSMITTER

1.   No switching of final relay:  Bad Q8 on X54-0001-00 2SA562Y.

2.   No drive:  C3 100pf in final box is cold soldered.

3.   Low output:  Check the plate load cap for touching plates.

4.   3.5 MHz low output:  Replace burned 47pf 3KV at load wafer.

5.   No TX:  Final choke burned out in final VOX L8.

6.   No RX or TX:  Bad common amp. Q1 3SK35GR in IF unit X48-1060-00.

7.   No ACC:  No plate current Q2 3SK41 If unit X48-1060-00.

8.   No TX relay:  Q8 2SA562Y on VOX unit.  Also R18 1K resistor relay
control.

9.   No TX or RX:  Check 9 volt terminal on FIX AVR (X43-1100-00) is loose.

10.  No CW TX: Bad 9 volt regulator.  Check D3 WZ061 on X43-1100-00.

11.  No TX:  Solder touch between TIF and key terminal on X44-1080-00.

12.  No drive to TX:  Check RL1 on GEN unit, small reed relay (X52-0010-
01).
13.  No ALC meter action on 10 meters:  This is normal for TS-520.

14.  CW chirp:  Q4 2SA606L on Fix  channel AVR X43-1100-00.

15.  ALC meter to maximum when TX:  RFI terminal at X44-1080-00 is not
soldered.

16.  No TX output:  82pf 3KV in final is burned.

17.  No TX output:  Q3 on RF unit 3SK41 X44-1080-00.

18.  No bias:  10 ohm cathode resistors burned in final VOX.

19.  No drive or TX output:  R70-71 RF unit, R5 Rectifier unit.

20.  No VOX:  Q8 in VOX unit X54-0001-00.

21.  No TX:  12BY7 is bad.  Shorts and burns out.  R71 and 70.

22.  No carrier output:  Q1 on Carrier X50-0009-01.

23.  No drive - no screen voltage:  R5 470 ohm open on rectifier X43-1090-
00.

24.  No drive - no ALC:  Q2 3SK35Y IF unit.  Q3 3SK41L RF unit.

25.  No RF output:  C13 0.04uf at pin 1 of S2001A is bad.

26.  Low mic gain:  Q1 2SC1000 on Gen unit.

27.  No TX:  Misconnection of brown wire after installation of CW filter.

RECEIVER

1.   Low Sensitivity:  Touching RLT and 9V at function switch.

2.   Receiver sensitivity:  No -6v at AVR:  Q8 2SC735 on X43-1100-00 is
bad.

3.   Frequency Shift:  Bad carreir Xtal 3395 on carrier unit.

4.   VFO drift:  C6 22pf, VFO unit.

5.   No receive:  Bad Q4, 3rd IF amp 3SK35GR on X48-1060-00.

6.   Receiver sensitivity and bias current jump, -6v unstable:  T1
oscillator transformer for -6v is bad on X43-1100-00.

7.   Erratic AGC action:  C11 100uf 16Von X431100-00.  Fix channel AVR is
bad.

8.   Frequency shift when warmed up:  Q1 in VFO 3SK22GR.

9.   No RX or TX:  If unit C59 touch to T12 IF transformer.

10.  Receiver noise:  Q5 3SK35Y X44-1080-00.

11.  Receiver sensitivity down:  NBI terminal is pulled loose.  Receiver at
IF board.

12.  No S meter reading and RF gain CCW.  No meter deflection:  Q3 on IF
unit.  Q5 on RF unit.

13.  VFO frequency jumped:  There is loose tension inside VFO.

14.  VFO frequency shift:  Cold solder of VFO output lead to VFO output
socket.

15.  Blows fuse when first on:  Check Q1 and Q2 DC-DC converter transistor.
One is possibly shorted.

16.  Noise blanker inoperative:  R6 4.7K resistor is broken at Q2 on X54-
1080-10.

17.  Loud audio squeal:  Q4 3SB473 on X49-0008-01 shorted.

18.  Low receiver sensitivity:  Diode D4 1S1587 on RF unit.

19.  VFO intermittant:  Wire to L1 in VFO is not soldered.

20.  No receive:  Q4 3SK35Y, Q5 3SK35GR on RF unit.

21.  No receive:  Q9 3SK35GR on IF unit.

22.  Hash noise in receiver:  Q3 on RF unit 3SK41.

23.  Blows fuse:  C31 power supply is shorted, 100uf 500v.  Also check
associated diode D3, D4.

24.  No RX on all bands:  WWV switch is broken or a wire is loose or not
soldered.

25.  Receiver sensitivity:  Q5 on RF amp 3SK35Y.

26.  Receiver sensitivity:  NBO terminal on X48-1060-00 is loose.

27.  Low audio:  Check for purple wire touch to ground at 12 pin connector
in rear panel.

(c) 102177TKC
                Copyrighted Kenwood U.S.A. Corp.
                Relayed with permmission from Kenwood U.S.A.
---------------------------------------------------------------------------
I haven't tried or verified this, proceed at your own risk.  WA2ISE


From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Newsgroups: rec.radio.amateur.misc
#Subject: TS520S service note: -6v supply
Message-ID: <1991Nov30.040656.19491@cbfsb.att.com>
Keywords: ts520
Sender: news@cbfsb.att.com
Organization: AT&T Bell Laboratories
Date: Sat, 30 Nov 1991 04:06:56 GMT
Lines: 27


copied from packet:
SB-043

TS-520S -6v Supply Failure                8-9-79

When troubleshooting a TS-520S, check all power supply voltages, including
the -6v DC supply.  Symptoms such as dead, blown 2A DC fuse and now dead,
low RX, no TX, or similar may occur after switching between 80 and 40M.

Cause of failure may be traced to an intermittent shorting between the 14v
dc and -6 dc supplies as the band switch is rotated between 40 and 80
meters.  This will weaken or destroy D8, a 6v zener on the FIX CH AVR unit.
To prevent repeat failures, break the White lead and install a 22 K ohm 1/2
watt resistor at the bandswitch S5-6, between the -6v supply line and
switch terminal.  An of course replace D8 on the FIX CH AVR unit, X43-1100-
00

New Part:  22 k ohm 1/2 W carbon resistor

Please annotate your service manual.

JEB/yn
(c) 8979TKC
COPYRIGHTED KENWOOD U.S.A.
==========================================================================
Note: I haven't tried or verified this, proceed at your own risk.  WA2ISE


From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Newsgroups: rec.radio.amateur.misc
#Subject: TS520/S service note on CW mode
Keywords: ts520
Message-ID: <1991Nov30.041026.19604@cbfsb.att.com>
Date: 30 Nov 91 04:10:26 GMT
Sender: news@cbfsb.att.com
Organization: AT&T Bell Laboratories
Lines: 20


copied from packet:
SB-046

TS-520/520S CW Frequency Shift                8-6-79

Reports of intermittent frequency shift during CW operation, on the order
of a few hundred cycles, may be traced directly to the Carrier Unit.

On the Carrier unit X50-0009-01, install a ground lead of #18 tinned wire
or similar, between the cases of T1 transformer and X3, the LSB XTAL.
Recheck frequencies after installing this ground lead.

Please annotate your service manual.

JEB/yn
(c) 8679TKC
COPYRIGHTED KENWOOD U.S.A. CORP.
===========================================================================
Note: I haven't tried or verified this, proceed at your own risk.  WA2ISE


 
Copied from the QRZ! Windows Ham Radio CDROM
 

From: "Greg Weremey" 
xSubject: Kenwood TS-520 Modification
Date: Tue, 14 Jul 1998 22:59:48 -0400

Mods for the TS-520 

Here are just a few mods that I designed for my 520.

1. Increased sensitivity.
 On the RF board, Q5 is the RF RX amp.  Notice that G2 is tied to the AGC line.
Bend G2 up from the socket, solder a 10k resistor to it and connect the other end of the 
resistor to the 9v line on the front of the board.  This will allow the FET to run wide open,
and you will have a better S/N ratio.  You will gain about two S units in signal and you 
may want to adjust your S meter to compensate.  I did this mod almost a year ago and 
have had no problems even with signals that were 40db over!  

2. Better audio.
 A few capacitors should be changed to accept a wider audio bandwidth.
These will only increase the BASS response and not the treble as it is limited by the 
IF filter.  Change the following on the generator board;
 C3 (1uF) to 10uF
 C4 (4.7uF) to 47uF
 C5 (1uF) to 4.7uF
 C8 (.047uF) to 4.7uF
 C9 (1uF) to 10uF
 C11 (4.7uF) to 47uF
 C10 (10uF) to 22uF
This will make the Tx audio flat.  Make sure that the Local Oscilator is adjusted correctly
or else you will have the bass attenuated by the IF SSB filter.

I also changed the caps on the AF board.
 C14 (.47uF) to 4.7uF
 C13 (.047uF) to .47uF
 C1 (1uF) to 4.7uF
You will also want to use a good speaker.  I have an old speaker box that got gutted.
I put in a 6x9 coaxial car speaker and it sounds great!  Since the audio is limited to 
4Khz anyway, don't go bonkers with tweeters.  You may want to play with a few caps
inside the speaker to roll off some of the very highs which will only be transistor noise 
anyway.

Along with changing the caps for flat audio, I installed two jacks for audio on the back
of the 520.  These are RCA female jacks that are used to connect to an equalizer.
Unwrap the wire on the generator board marked MA O.  This is the output of the 
Microphone Amplifier.  Connect some microphone coax from this terminal to your 
RCA socket on the back of the rig marked output.  Remember to ground both ends of
the cable so you won't have hum/RF problems.  Now connect the other RCA socket via 
mic cable to the wire that you unwrapped from the MA O post.
Make up a jumper cable for those times you don't want to use the EQ.
I recommend an old Radio Shack 5 band EQ.  I have no RF problems at all and I run
500w PEP with the amplifier sitting next to the Kenwood.  Stay awayf from EQ's that 
use all IC's.  I find regular transistors are better for handling RF.

3. Amplitude Modulation
This radio can talk AM in a pinch.  You will be limited to SSB reception though.
That's OK if you don't mind playing with the RIT to get rid of the beat tones.
I decided it was degrading the specs when I put in a regular AM detector so I pulled it out.
Here is how you make it talk.
Get a DPDT relay (12v) and connect it inline with the fixed channel selector switch, so
that when you select crystal 4 the relay energizes.
Now lets take the relay in two sections.  The first is connecting the ouptut of the 
mic amp into a matching transformer via this relay.  You want it connected so that
the MA O is on the wiper and the relay NC1 is connected to the Balanced Modulator.
Connect the other relay terminal NO1 to the low impedance side of the transformer.
Connect the other lead of this winding to ground.  So when you select fix channel 4, the
relay energizes, and disconnects the mic from the balanced modulator and connectes it
through the transformer to ground.

Ok now the second part of the AM mod.
Take the HIGH impedance winding of the transformer and connect one leg to ground.
Take the other leg and connect it to a 47uF cap.(neg lead)
Connect the positive side of the cap to an 820 ohm resistor.
Connect the resistor to the 9v terminal (on the RF board or most any other board)
Connect the junction of the resistor/capacitor to the NO2 terminal of the relay.
Connect the wiper of the relay to S on Q3 on the RF board.  I found R17 to have its
exposed wire connected to S on Q3.  Simply scratch the paint away on R17 and solder
to the resistor.  
Since this design modulates after the IF, you will have full fidelity and bandwidth of
your audio.  If you use an EQ, don't be excessive with the highs or you will have 
enemys from the splash you create.  Also, there is no limiter here.  If you have 
access to one, install it in the EQ loop.

Have fun on 80M!!

73's                                                                 

For more info or if you have questions;
Please visit our website at http://www.angelfire.com/ma/electroservepro
Greg Weremey  (N1JFE) - Electronic Service Pros. 
electroservepro@iname.com


 

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