Dual Rectifier Problem

Hi guys, I'm new so sorry if this is in the wrong place or whatever.

I've got a Mesa Dual Rectifier, one of the old 2 channel models. It has worked fine in the past but recently, after not using it for several months, It packed in on me. This is what's happening now:

When I flip the first power switch, the amp switches on momentarily, then off. The fuse is blown. I tried to isolate the problem by removing valves one by one, blowing several more fuses in the process, and found that the amp switches on when the two rectifier tubes (5U4GB) are removed, but there is obviously no sound from the amp in this case. Does this mean that the rectifier tubes are blown?

Also, this happens when I set the rectifier switch to "Vacuum Tube", but when I set this switch to "Silicon Diode (Hi Power)", the amp powers up without blowing the fuse. However, in this case again there is no sound at all from the amp with a guitar plugged in.

Any help appreciated, because I'm in England and it's pretty hard to find a tech who'll go anywhere near a Boogie amp.

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BUMP

It does sound like your rectifier tubes are bad. But if you use the SS rectifier and still have no sound, you may have blown something else in the process.

Try pulling the power tubes, and the Rectifier tubes. Then see if you get any sound out of the effects loop. This will tell you if it's in the power or preamp section.

I blew the screen grid resistors in the one I had because I had it on the 6L6 setting when I put EL34's in it. Cheap fix if you can solder.

One thing to do would be to open it up and look for blown or burnt components. But be sure to read up on draining the caps and safety info before touching anything inside the amp. It holds enough voltage to kill you if you don't. Even unplugged.