Amp problems. Bad tubes?

[monroe]

Hey Now!

Not sure which forum is the right spot for this, so I'm putting it here...

I've got a problem with my Fender Hot Rod Deluxe that needs diagnosin'. Definitely a preamp issue. If I use another preamp and go straight into the power amp of the HRD, it works fine. However, when I plug into the amp the "regular way" (i.e. using the preamp), I run into problems. When I first plug in, everything is fine. But after a short period (sometimes seconds, sometimes maybe a few minutes) it goes boffo. And by that I mean, it loses almost all power(volume). I really hope it's a bad tube, as that'll be easy and cheap to replace. Does this sound like a tube issue?

A buddy has some extra tubes laying around, so I'm going to grab a couple today and see if swapping them out will take care of the problem. Fingers crossed.

[sants]

Could be a cold solder joint and when the amp heats up you are losing signal. I would think that if the tubes are outputting sound for a few minutes and then the volume drops it isn't a tube issue. In my experience, when a tube goes it goes.