Dennis
I had this problem once in a old HQ170 and it turned out to be the C in the vfo LC circuit. It was a nice looking mica capacitor and I didn't think at first that it could be the problem but after all the other things I changed once I replaced it all was right with the world again. Steve NU0P _____ From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Dennis Monticelli Sent: Monday, August 23, 2010 23:59 To: pony...@aol.com Cc: drakelist@zerobeat.net Subject: Re: [Drakelist] unstable R4C PTO 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, <pony...@aol.com> 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 Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
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