Marshall JMP-1

[Grubey Doo]

I have one of these and the effects loop is losing the signal before the return. It looks like as soon as I engage the loop, it has a mix control, it automaticall biases the fet and NPN xsistor for the mute_effects circuit. The schematic is at:

http://www.drtube.com/schematics/mar...jmp1-61-04.pdf

Any ideas?

[Grubey Doo]

I also swapped out tr10, the BC184. The only thing I can think of is the J174 FET. Maybe it's just sending the signal to ground.

[Grubey Doo]

I'm answering my own posts.
Apparently the FET serves as an active attenuator
in parrallel with two resistors. I removed it and actually I think the circuit works better without it.

[alex_21]

hy , i need some help.... my Marshall JMP-1 transforme broke down. can anyone tel me where to find data from the transformer or where can i buy a new one. tnx

[Alex R]

Marshall sold me one about 9 months ago, I imagine they still would.