Line 6 Spider II - noise and channel switching issue

[donr]

I have a Spider II that I bought from a friend.
The issue I'm having is that while the amp is on it makes popping noises, will increase volume briefly and then come back down to normal volume.
This happens whether a guitar is plugged in or not.
It will also switch channels on occasion while I'm playing it.

I took the head apart to look for loose wires or possible cold solder joints or bad grounding but nothing was obvious.

Please provide suggestions.

thanks

[jknopp2]

I had that problem and it ended up being the ripple filter electrolytics.