Strange amp problem

[Spivonious]

I have a Genz-Benz El Diablo 60 combo.

It's great.

The problem is this: when I turn the volume knob all the way up or all the way down, or I unplug the cable from the guitar, I get an electronic noise...like an infinitely-long beep from a computer.

Any ideas on what could be causing it? My cable is fairly new, and a name brand. The volume pot needs to be changed, but since the noise happens when the cable is unplugged too it seems to me that it's not a guitar problem.

Has anyone ever heard of this happening?

[Inazone]

Have you put the amp into standby mode? Is it possible to disconnect the internal speaker(s) while on standby, to determine if the noise is coming from within the amp electronics or somehow making it through the speaker?

[Spivonious]

I'll try that when I get home tonight. I never thought it was the amp before because I know the volume pot is on its way out so I just assumed it was that. But then the cable came out and the sound was constant.