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Amp death.Transformer Question.


mule73

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Well, I was messing around w/ some different speaker cabs, got careless and took it off standby with no speakers attached. Big blue arc around one of the tube sockets(power tube), blew a fuse. Replaced the fuse and now it blows the fuse everytime I take it off standby.AAARRRGGGHHH! I am SO STOOPID!!!:mad: :mad: :( :( :cry: :cry:

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Originally posted by mule73

Well, I was messing around w/ some different speaker cabs, got careless and took it off standby with no speakers attached. Big blue arc around one of the tube sockets(power tube), blew a fuse. Replaced the fuse and now it blows the fuse everytime I take it off standby.AAARRRGGGHHH! I am SO STOOPID!!!
:mad:
:mad:
:(
:(
:cry:
:cry:

 

I'd say to replace the output tubes and try again. Then, perhaps the screen grid resistors blew, and/or the output sockets got carbon traces from the arcs on them. The power transformer is the last thing in this case I'd suspect (although it is possible). And if that damage happened as you described, you'd only be solving the symptom by replacing the PT, *if* the PT had died. The cause has to be fixed, which is new tubes, possibly new sockets, and possibly new screen grid resistors. If you don't take care of the rest of this, the new PT would die as well.

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Thanks for the help man. I opened 'er up and there is carbon on the power tube sockets. doesn't seem to be any signs of burnt components on the board, but I don't really know what i'm looking for, so I'm not gonna mess with it. I'll take it to my buddy tomorrow.Man, I hope my tranny's ok. New set of Svets down the drain. Wish I had been drunk, then at least I'd have an excuse. This sux.:mad:

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Ah well, no biggie. The PT is probably ok, I'd say you have better than a 50% chance of that anyway. The fuse most likely saved the PT. The output transformer could've taken stress from this too though, not that I want to worry you (I'd say the OT is probably still ok), but if an arc happens that means the OT has seen considerably higher voltages than normal.

 

As for the rest--if you can replace the sockets that arced, that's best. If not, carbon might be under the socket (as well as on top), and depending on the material it could be through the material from pin to pin. So replacement is recommended. Cleaning with a wire brush might work but some carbon might remain and the next set of tubes could fail sooner or later.

 

The screen grid resistors should be checked for sure. You can follow the screen pin's connection to the resistors on the board (probably 470 ohms each) and check them with a meter.

 

Good luck.

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