Zener diodes can develop an instability in their voltage "knee" value due to migration of mobile charge at the surface of the semiconductor. A random walk of a few tens or hundreds of mV could produce your frequency problem. Put a scope probe on the zener and set your scrope for high sensitivity. See if you observe a "jumpy" voltage.
Dennis AE6C On Mon, Aug 23, 2010 at 6:37 PM, <[email protected]> wrote: > Hi Gang, > > Thanks for all the replies to my past message, but at this point in time, > I'm even more dumbfounded than ever. So far I have cleaned, and oiled the > mechanical parts, installed a ground strap on the PTO, resoldered all the > ground wires inside. everything is free, and working as it should. Also, I > drilled another hole in the cover to stretch that angled spring giving more > tension. > > No avail, now I think it must be an electronic problem, as sometimes, > when I try to tune a station, it warbles, sometimes while I am just > listening hands off. vibration doesn't seem to change anything. > Someone emailed me suggesting the zenner diode could be the culprit. I > always thought most solid state devices either work, or don't work. Is it > possible that's the problem, or could it be somewhere else outside the PTO? > > Thanks for reading this....................Tom, WD8JPP > > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist > >
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