[Collins] KWM2 feedback

[john]

Thanks to help gotten here, and some hours under the hood, I've gotten an 
early KWM2 playing pretty nicely. One interesting problem remains.

If the rig is in SSB transmit (either USB or LSB) and the audio gain is 
advanced more than half way, audio feedback occurs....now the wierd part of 
this is that the feedback is not coming from the attached speaker...I'm 
wondering if there is some piezoelectric effect that accounts for it....its 
coming from the rig itself.

If I turn the AF gain up, (again, during SSB transmit) the amplitude of the 
feedback increases, but it's not being coupled into the transmitted signal 
(there's no power out, no change in grid or plate current).

It's quite loud!

Any ideas where to look? All other functions appear normal. 6146s have been 
changed (for another reason) and there was no change in this phenomenon.

Ideas?

John K5MO