[Kenwood] TV506 22MHz Oscillator problem

[Dr. Gerald N. Johnson, electrical engineer]

That's a lot of shift for a good crystal. Just a little too much for
external influences, like the trimmer capacitor going open (which you
could check with a quarter drop of DeoXit where the trimmer shaft hits
the clip, if its not mounted flush to the PC board to make that point
inaccessible). You could check for fundamental operation by putting your
scope probe on the crystal terminal. I had a new factory crystal once in
a computer board that ran at three frequencies at once. Confused the
serial port rate clock considerably. I added a 56 PF capacitor to the
feedback path and it calmed down to the right frequency (emitter to
ground or base to emitter, I don't remember which now). And as far as I
know may still be working decades later.

Series/parallel mode is set by the circuit not the crystal. I suspect
the crystal, junk inside is moving around and changing the load on the
crystal or the electrode connections are getting bad to shift the
frequency that far.

73, Jerry, K0CQ

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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.