marshall avt50h valvestate...question for the gurus

[tele_guitarist]

I'm hoping someone can help out this old 'hack' here.

I plugged my valvestate (while turned on) into a cabinet and it fried the fuse, R58 and R81 which are both going to ground on page 2 of this schem:
http://www.indyguitarist.com/schemat...vt50_60_02.pdf

(look by w1/w2 the "loudspeaker out" and "headphone output").

It also fried the 7293 power IC as well as the fuse. I put another fuse in, fried the IC and the fuse again. I can't see anything else wrong!!! Is there anywhere else I should look in your opinion?

Also, my BIGGEST question is more of a reality check for me I guess
I just want to run the preamp into a tube power amp, can I just disconnect before IC5a (which is a gain boost stage after the effects return)? If so, I won't need to replace or fix the power amp problem, correct?

Thanks a ton for any input!!!
More schems:
http://www.indyguitarist.com/schemat...vt50_62_02.pdf
http://www.indyguitarist.com/schemat...vt50_61_02.pdf

Brian

[Enzo]

You only want it as a preamp? Just disconnect the power amp module and forget it then. Two little connectors - pull them. leave the dead soldier on the heat sink, then no parts will get lost for when someone wants it to be whole amp again.

In the name of science however, if R58 burns, then the amp was kicking out high freq for all it was worth. probably oscillating. I would suspect beyond the 7293 itself that something around that IC hasd failed - C15 above it or the five small parts below. Also possible something ugly happened in the reverb return and it went nuts. The feedback circuit just to the right of hte 7293 could also have a problem.