Madison Divinity Blowing Mains Fuse

[chunkitup]

A friend asked me to help him fix his amp. I said what is the problem and he said that he was in a hurry to play his guitar and inserted the return cord from his pedals into the speaker out jack by mistake! Ouch. Now whenever he flips the SB the B+ fuse pops. What sort of trouble did he get himself into?

[Enzo]

Forget you know HOW he screwed it up. Approach it like any other amp.

Isolate the problem. Pull all the power tubes. Still blow fuses? If not, then you had a bad tube. If so, then disconnect the primary center tap wire on the output transformer from the B+. Still blow?

[tboy]

Forget you know HOW he screwed it up. Approach it like any other amp.

Nothing to add here, I just thought that gem of wisdom should be repeated.

[chunkitup]

Thanks enzo. I will do just that and get back if problem not found.

[chunkitup]

Alright so the first problem was he was using 5A fast acting fuses. Changed to slo blo and with the tubes out and stand by on the fuse does not blow. I put the tubes back in and when I turn the power on and standby off there is a bad hum.
Also I can not find a owners manual online probably due to the company not being in business anymore. But there is a switch for the output impedence that just says 4 and 8. I have no idea which is 4 and which is 8. Also the output jacks are not labeled so if anyone knows which is which please let me know.

[chunkitup]

Since no replies in a few days this is what I came up with and someone let me know if this needs more searching. The amp is fine when tubes are out and the standby is on, fuses do not blow. Put the tubes in and the fuse blows when engaging the standby. I am going to replace power tubes. Anything I am missing?

[Intergalactic Tourister]

he was using 5A fast acting fuses. Changed to slo blo

Use the same fuse as stated in the amp. Changing it won't solve anything but could definitely harm something.

Pull all the power tubes. Still blow fuses? If not, then you had a bad tube. -Enzo

So, if it doesn't blow a fuse with the new power tubes then you know it was one of the old tubes.

[defaced]

Check the screen resistors while you're in there.