Mark III 80hz slider problem..

Ok so I’m the new owner of a black dot Mark III. The only issue that I’ve found is that when I engage the GEQ, the 80hz slider will emit a loud droning hum if it’s placed near the top line or the bottom line. It has a range in the middle where it works perfectly and sounds great, but moving it up or down too far will cause the issue. Like I said before, it’s a loud hum, and when I strum the guitar, no noise comes from the speakers other than the humming. Does this sound familiar? Any help or advice would be appreciated greatly.

The slider (linear potentiometer) probably needs to be replaced.

I'd recommend replacing all five at once.

Technician skills required.

Parts available from Mesa.