[Kenwood] TS-940S: AF Tune control operation unstable (oscillation at some points) - advice?

[David Feldman]

Have TS-940 S/N 7M range. In CW mode, with AF Tune button active, adjusting the AF Tune control results in some apparent oscillation or similar instability. There is a tunable gain/level peak (I think normal operation; I'd not ever tried that control before on a TS-940), however, rotating the control across the range also produces unstable, sharp (and fairly loud) audio tone artifacts at some points.

Advice request - does this sound familiar to anyone? I'll have to open it up anyway for another issue (the backup battery is also now dead), but would like avoid reinventing the troubleshooting wheel if this is otherwise a known type of issue.

Thanks,

Dave
wb0gaz at yahoo.com