Harmon Kardon phantom volume fix

I have an AVR 300 with a phantom volume problem (goes up and down by itself) . I haven't been able to find a fix even in the Harmon Kardon service manual. They mention it but no directions on how to fix it. Anyone have any ideas what could be wrong?

If the volume control is an encoder type switch then try disconnecting it and see if the problem still happens. It could just be a dirty or worn contact in the encoder.

My Arcam has a similar issue but only when actually turning it - it can go up or down even when you are actually just turning it down.

Agreed, such problems are almost always a faulty rotary encoder - often carefully stripping them down and cleaning them can cure it (I always give the contracts a little 'bend' as well to increase pressure).

Yup, oxidation of the contacts is the usual issue I have run across in the past. A good clean and as Nigel said, re-tension the spring contacts usually cures the problem