gallien krueger 200mv. Echo issue

[Garydean]

I have a gallien krueger 200mv with an Echo problem. The Echo function never completely turns off when dialed to 0 and a static noise is heard, only when you pluck a string while the knob is at 0. Turning the knob to increase the echo does in fact raise the echo effect and the static issue goes away. I'm thinking it's the pot that is shot. yes...no?

There's also a very small green on/off switch (actually says on/off) located on the board, by the XLR jack. It's in the off position now. Does anyone know what it's purpose is?

Thank you!!

[drumwood]

The switch on the board is for phantom power.

I have a 200mv also with an echo problem. The problem is no echo at all...the echo knob makes no difference in the sound.

Any ideas?