RV-3 Troubles

[petemoore]

Boss RV-3, bought about 12 years ago.
 Now that it's acting up' I'll fix the loose Mix knob, I don't think any wires are broken, all the knobs work like they did when it was new.
 Problem is it adds noise when processing signal, quiet when I stop playing. Sounds like 'processing noise'...[I don't really know...] a very slight soft tick to a modulation or something, seems to be the same pitch [if any..], basically a background noise starts when I do.
 Also it seemed the noise started a while ago, IIRC less of it, and could be 'reset' to normal operation by lifting power supply then restoring power.
 I know this isn't much to go on, I haven't even pulled the circuit out yet...trying to plan my approach, would rather be able to put it off more, but it seems necessary today, the power restore trick doesn't get rid of the noise now.