CRYSTAL TESTER
Cost estimate: $7
Your 80- or 40-meter crystal oscillator isn't oscillating - what's wrong? Is it a wiring error? A solder bridge? A faulty component? Maybe it's the crystal! A simple circuit that tests whether or not a crystal is good, this is a real chestnut. I first saw it in the October 1989 issue of Popular Elecronics but the original circuit is credited to Mike Kaufman in Wayne Green's out-of-print book Practical Test Instruments You Can Build according in an article in 73 Amateur Radio Today (1/92, p.22) that updates of the circuit by featuring an output for an oscilloscope or frequency counter and uses an LED instead of the lamp shown. I am offering the original tester here because I built it years ago and it still works well.
How it works: A crystal-controlled untuned oscillator composed of Q1 and its associated components "turns on" Q2 if the crystal oscillates; Q2 in turn lights the lamp. No oscillation, no light.
Construction and Operation: Parts layout is not critical. If possible, first prototype the circuit on a breadboard to see if it works. To check the tester, use a crystal of a frequency you can monitor on your receiver, put the tester close to the the input of the receiver and close the switch. If you hear the signal and the lamp lights, the crystal, tester, and receiver all work. After that test, you can assume that if the lamp lights a crystal under test is good.
The tester should operate well for any crystal with a fundamental frequency from about 2 to 8 MHz. Harmonics are also generated by the tester, although due to the lack of tuned circuits overtone crystals will oscillate at their fundamental frequency.
COMPONENTS:
Resistors
1/4-watt units OK.
Capacitors
Ceramic-discs work fine.
Transistors (Q1, Q2)
Almost any common NPN; cheapo plastic-case 2N2222-type transistors are fine.
Lamp
Any miniature 6-Volt lamp will do instead of the GE #2180.
Crystal Holder
Anything that works. I use alligator clips soldered to hookup wire.
Misc. Materials
Socket for lamp, switch, 9-Volt battery, box, solder, hookup wire, etc.
..need parts?...
***HOME***
***RECEIVER***
***Q-MULTIPLIER***
***2-BAND VFO***
***500mW TRANSMITTER***
***3W 2-BAND TRANSMITTER***
***15 METER CONVERTER***
***15 METER VXO-TUNED TRANSMITTER***
***FIELD STRENGTH METER***
***WATTMETER***
***SUPPLIERS***
comments?
email: jandg@brink.com