Marshall bass 100 solid state transmitter

ruteng

Member
2011-03-31 3:36 pm
Hi all,
I have this marshall ss amp on the bench that oscillates on the negative rail at around 20k. I have replaced all the transistors, caps, bias pot in the power amp section. It draws so much current, (2.4A @8vdc thru the .33 ohm mj2501 emitter resistor) I cannot power it at more than 8vdc using the variac. If I remove the wire to the base of the MJ2501, it stops oscillating and I can bring it up to 40vdc @120vac. I have another 2501 ordered although it tests good.
If anyone can help me get this thing off my bench and back to the very patient customer, I will be very grateful. See attached diag.
Thanks, Rudy
 

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