M80 Problems

[M1A]

The M80 seems to work fine in passive mode. In active mode it has a humming and loud scratching sounds. This happens as soon as it's plugged in, not a result of playing. I bought it used without a battery and didn't try it in active mode for several months. Any idea what it could be? I've tried different inputs, cables, strapjacks and it's always the same.

[Caleb_Elling]

Hey hey, M1A
Do you know if the volume control is causing any issues? This does't sound like anything I've heard of before, so it's difficult to say what could be wrong.