1568A Help, please.

**1568A** · March 15th, 2004, 01:36 AM

Hello gentlemen,

I am in desperate need of help because I can't seem to figure out why my 1568A is blowing fuses. I'm a guitar player, hence my limited tech skills.

I have replaced all the caps, including those on the board.

I noticed that the 4.7K resistor between the two filter caps looked dark, so I replaced it.

When I turned on the amp, once again the fuse blew (after about 15 seconds like it has been doing), but this time it totally fried the new 4.7K resistor. I also heard the sizzling going on inside the amp. forums

Any help or advice would be greatly appreciated.

Thank you very much,
Gary

**Todd W. White** · March 15th, 2004, 01:41 AM

You either have a bad tube(s) or one of the transformers is fried.

Try pulling out all of the tubes, then powering up and see if the thing blows fuses.

If not, turn it off, and add the rectifier tubes, one each.

If these can be added and it doesn't blow the fuse, the power transformer is probably ok.

Next, try each of the 6CA7 (EL34) output tubes, adding them one at a time to see if the fuse blows. If it doen't blow, use the process of elimination to try to isolate the problem (after you replace the burned fuse, of course).

If eithe of the transformers are gone, you're sunk.

Hopefully you haven't been playing guitars through this amp....

**1568A** · March 16th, 2004, 02:16 AM

Actually

...yes, I've been using this amp to run a Marshall preamp for about ten years with no problems until now. The sound is (was? forums

) absolutely beautiful.

I hope on of the trannies is fried. I'd hate to have to try and find another.

I'll replace the resistor and try turning the amp on w/o tubes.

The thing that baffles me is that the amp seems to work fine for about 15 seconds. Could it be that one of the windings on a tranny is shorted? forums

I'll post back later tonight or tomorrow with my findings.

Thank you VERY much!