i have an MF-101 filter that produced a really annoying high pitched noise at any settings, no matter where i plugged it in the house. I thought it wouldn’t hurt to clean it since these beasts are getting old. I simply opened it, removed the board from the pedal and cleaned it with a contact cleaner spray + cleaned every knobs and selector (spray inside the tiny holes).
results : no more high pitched noise ! i thought it would be useless, i was wrong.
Try it !
cheers
Ok, I opened my low pass filter up. All looks super clean. But I have that noise. What spray did you use? I only have wd-40 at the moment. 
You can’t go wrong with Deoxit. WD-40 would probably not be a good idea…
In my understanding, WD-40 is more suited for mechanical problems rather than electronic parts
Might it be the power supply? I had an issue with one (non-moog) power supply causing a high pitched noise. Try a different supply if you have one.
And not very good for that either…
Never but never use WD-40 for anything electrical. You will ruin the electronics.
Stephen
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