Original DOD FX50B oscillates

[yeeshkul]

I got one unit for repair and noticed that when all three knobs are all the way up, it oscillates. I changed both input and output wires (the terminals are very close to each other) for shielded wires and it helped a lot but i can still hear a mild squeal when i switch to the neck pickup. When i unplug the guitar cable from my guitar it oscillates really loud.

Is this the way they should behave? Can anyone check it out for me or help with any idea?

[askwho69]

show the pcb, schematic or something?