DIY HiFi Forum

Joplin blown fuse

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Hi,

I've got a loaned Joplin amp here and after a few hours use it has blown a fuse. Half a second before it blew, I heard a brief, load hum and may have seen one of the valves flash or brighten out of the corner of my eye.

None of the valves has a short that shows up with a multimeter. Filaments are all fine. I've slipped off the bottom cover and I believe it's a factory build (red paint on all the screw threads) and it looks like a self bias circuit.

Can someone give me a tip on what to check? Cathode bypass caps and coupling caps are the obvious culprits to check. What else should I look at?

Cheers,

Jeff

Follow Ups:

RE: Joplin blown fuse - bcherry 14:45:06 10/06/09 (1)
- RE: Joplin blown fuse - jeff mai 12:40:43 10/08/09 (0)

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