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

[k3ac at aol.com]

Dave - well, the AF Tune pot on the 940 is not used very often (at least I don't recall using it much when I had my 940 on CW)  so I suspect (at least an initial step) that it may have developed some corrosion internally. Are you able to get to it at all without removing front panel? If so, might be worth shooting a little Caig FaderLube (not DeOxit) inside and working the control to see if that improves the instablity/oscillation. Getting to the opening of the case under the solder terminals can be difficult but you may be able to get a thin straw-like applicator close enough to get some of the lube inside.
Bob, K3AC
In a message dated 12/2/2018 10:35:40 PM Eastern Standard Time, kenwood at mailman.qth.net writes:

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,
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