OK, I?m stumped. My OMNI-C lost 4 diodes on the SWR/TR board a while back
and I replaced them and the AGC circuit works again, but after some use on
CW the receiver will start to drift up and down in frequency by 100 to 200
cycles and then it will start to make noise in addition. During transmit
this produces a warbly chirp. Turn the radio off for 10 minutes or so and
it will start up and run fine for a while. The power supply seems fine but
I?ve tried another and the same effect is occasionally observed. I have an
OMNI D that does not seem to have a problem with either power supply. If I
connect and use the external VFO, the same problem can occur, so I do not
believe the PTO needs rebuilt or any of that type of thing. I?m fairly
certain the problem is either voltage regulation or an oscillator that warms
up and becomes unstable, hence the noise.
So any suggestions of what to look for and where to look, in this old but
beautiful OMNI C ? I bought her new long ago and now I see it in the Ten
Tec museum, and some call her vintage, but I hate to let this rig go down.
Any suggestions of what could cause this anomaly will be appreciated.
Ron
KA7U
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