Help me diagnose this amp problem:

[Xeromus]

Okay, My crate VFX5112. 50w EL34 amp. I've had it for a few years, lightly used, still has original groove tubes. Has digital effects built in, switchable via footswitch.

Lead channel works fine, no change.

Clean channel will be at regular volume then slowly drop out til it's inaudible and then pop back up again real fast. Sometimes switching the effects on/off makes a difference in volume. As in it'll pop back up or a little bit louder.

Tube change in order? Something else? Like I said, it seems to only be a problem on the clean channel.

[Scott_F]

Re: Help me diagnose this amp problem:

Chances are great that it is a preamp tube. Generally, on a two channel amp, they are using different preamp tubes. Sounds like I'd swap a good one in the V1 spot. I'd bet that your problem lies there. All this is based on the fact that your lead channel sounds great.

[Xeromus]

Re: Help me diagnose this amp problem:

I was thinking the same thing Scott. Btw, damn you're fast, I was hoping you'd see this. Upon further investigation, the effects switcher in fact does nothing, scratch that. The clean channel will drop in volume til it's near inaudible then get a little fuzzy and stay that way. The 2nd time I tried it just now it worked fine and didn't do it at all. I'm gonna have to pick up some pre tubes later and try it out. Sounds like it might be a quick fix.