Valvestate problem - low volume

[brad]

I was given a broken Marshall Valvestate VS265 by a friend who was unable to repair it. As far as I can tell, here's what happened:

1) Pre-amp tube blew
2) Mains fuse blew
3) Fuse was replaced with increasingly larger values until it stopped popping
4) Output transistors blew one by one

I've replaced the fuse, tube, and output transistors, but I'm having trouble figuring out what else is broken. The volume is very low, even turned up to 10, with quite a bit of distortion on the clean channel. Output from the FX Send jack is good (loud, clean, etc), but output from any of the others (DI Outs, speaker outs, internal speakers, headphones) is heavily distorted.

Any ideas would be greatly appreciated.

[Enzo]

How does a preamp tube "blow" exactly?

If the preamp tube somehow shorted, it might have damaged something. Is there reasonable voltage on its plates? Oh wait, it the loop send is OK, then so is the tube.

All of those distorted things come off the power amps. From your post it sounds like both channels are similarly affected. That tends to mean the same fault affects them both - somehting in common. Are both power rails OK? How about the mutes at the power amp inputs? TR5, TR8? Are they on? SHouldn't be.

Pull CN2 on the power amp board - those are the inputs to the P/As. Can you inject a signal there and get results? Divide and conquer.

What did you replace the output transistors with? If you substituted, you do realize those are darlingtons, I hope.

The signal from the preamps comes from the duaghter board also CB2 there. Is the signal clean there? If not, trace back UC11, IC9 and 10, IC9 only when chorus is on. IC4.