Need help with Fender Twin Reverb

[James_Allen]

Hello, this my first time on this board. I am having some trouble with my Fender Twin Reverb. This just started happening and here's what it's doing so far. When I play louder (not even that loud though really) the sound breaks up in a very undesirable way. Kind of crackly and muddy at the same time. It seems to be worse on the reverb/tremolo input than the other. Also, I have an MXR Phase 90 that makes it much worse and a Boss EQ pedal that seems to make it a bit worse too. Please tell me what the problem might be and how to troubleshoot and hopefully repair myself. I don't want to have to take it to the costly repairman. Thanks.

[loudthud]

What's been the general history of the amp? Has it been used regularly for the past 30 years? Ever stored in an unheated garage?

The first thing is to verify that the speakers have not gone bad. Try to play the amp into another speaker cabinet and try plugging the speakers into another amp. Sometimes one of the speakers goes bad but the one good speaker masks the toasted one.

Next the tubes. You have to swap in known good tubes one at a time and try the twin's tubes in another amp. Any unusual red glows from the 6L6s?

That ought to keep you busy for a spell. Report back. Next is the dangerous part where you open up the amp. Do you have any experience working on electronics?

[James_Allen]

Not sure the exact history. I bought it from a friend a little over a year ago and I have played it regularly since I have had it. I don't know how often he played it. He bought it new in 2000 or 2001 though. I think he had it in his garage for a while but this is in Austin, TX so the garage was definitely not heated.

Just plugged it in to an external cab and it did the same thing. Does it matter that I was still using the internal speaker? The external was definitely having the problem as well. I don't have another amp handy at the moment so I can't do the test on the Fender's speakers with a different amp.

Tubes: the 6L6s look to be glowing the same. As far as testing the tubes, again I don't have another amp around at the moment. Any other way to test? Do the preamp tubes need biasing when you swap them like that?

As far as the dangerous part, I'm not so sure I'm equipped for that.

Thanks for the help so far and any other advice is greatly appreciated.

[Gtr_tech]

If its a re-issue we're talking about then they're not built like the old ones. There's the standard Fender PCB in those and they are prone to the same pcb related problems. Cracked solder and the like.....I'd bet thats whats causing the strange rattly noise. Either that or an output tube is on the way out mechanically.

[loudthud]

If its a re-issue we're talking about then they're not built like the old ones. There's the standard Fender PCB in those and they are prone to the same pcb related problems. Cracked solder and the like.....I'd bet thats whats causing the strange rattly noise. Either that or an output tube is on the way out mechanically.

I was wondering about that. Not sure if it's a point to point amp or PCB with those ribbon cables to the tubes and pots.

[James_Allen]

Thanks for the help guys. It is a reissue. I'm not very experienced with tube amps. What is my next step at this point?

[Gtr_tech]

Best take it to a tech. A good one will be able to have you back in business with minimal expense.