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Crash Gordon
Drive It Like You Stole It

Smyrna, GA

1 recommendation

reply to aurgathor

Re: Marshall MB450H Schematic

Curious minds want to know!

I hate the "I've fixed it/solved the problem" without WHAT fixed/solved it posts. Please enlighten us. Inquiring minds want to know.

Had someone before you had a similar/same issue AND posted the fix for it/details, it might've made it easier for you (and anyone else afterwards)

Although with a brand like Marshall (amps) , they want their gear working, so direct contact works well, I know Mesa Boogie/GK/Trace Elliot does.

Starting with the obvious:

one output transistor on each bank of the output stage had a C-E short.

Less obvious was a current steering transistor earlier in the circuit which was pulling the + bank toward the pos rail.

Finally, a quad op-amp near the input stage. That was it.