Power Supply probs - I'm a novice, HELP!!

[MisterUrOnFireMister]

Hello,

New to this forum and to tube amp repair in particular. Just need a bit of advice...

Got an old Carlsbro amp, has been good as gold until the other night when it shut down. Checked the fuses, and sure enough, the HT was fine but the mains had blown. So, I get a new fuse and pop it in there. Get power for about a second or two and then the fuse blows again. Have tried multiple fuses, still the same results.

Is this an easy to fix problem? Is it something scary? Any help you could give would be much appreciated!

Sam

[mykey]

Got an old Carlsbro amp, has been good as gold until the other night when it shut down. Checked the fuses, and sure enough, the HT was fine but the mains had blown. So, I get a new fuse and pop it in there. Get power for about a second or two and then the fuse blows again. Have tried multiple fuses, still the same results.

does the fuse still blow with the power tubes removed?
if it does not blow you might want to change output tubes, if it does still blow you could suspect a shorted diode in the power supply. anyhow from what you have described, I would suspect a shorted diode.
what size fuse is the HT?

[MisterUrOnFireMister]

Its a 2amp slow-blow/time delay. I'm UK-based, if that makes any difference? I'll try the power tubes later. Thanks for the advice!

[Don Moose]

Basically, the fuse is popping because there is some OTHER problem - the ufse just keeps it from catching fire.

That you're in the UK, using an amp intended for UK mains voltages(?), makes no important difference once you're on the secondary side of the power transformer.

Do you have a multimeter (VOM, DVM, tell us which)?
Have you ever been inside a tube amp (familiar with the safety issues)?

It's probably something simple, but bypassing the fuse - or putting in a bigger one, is a very dangerous and destructive way to find out what.

R.G.Keen's Tube Amp Deebug page is a good place to start.