samgraysound
Well-known member
hi all,
I'm working on a Marantz 2385b. The R channel is siginificantly quieter then the L. I've isolated the problem to the Pre and Tone Amp pcb PE01. Specifically the op amp at the output of the board.
There's some weird voltage readings:
QE06
B = -18.55v
C = 18v, kind of wobbly. Should be -0.2v
E = -18.67
And on the diff amp QE04
B1 = jumps all around between 0 and 5v. Should be 0v
C1 = -18.77v
E = -10v, jumps around a lot. Should be 0.5v
C2 = -18.74v
E2 = -0.001v
I've replaced CE32, CE34, CE36, CE38, CE40, and QE06. I've tested all the resistors out of circuit and pulled QE04 and tested both sides with my transistor tester.
I'm out of ideas. What do you suggest? Schem attached
I'm working on a Marantz 2385b. The R channel is siginificantly quieter then the L. I've isolated the problem to the Pre and Tone Amp pcb PE01. Specifically the op amp at the output of the board.
There's some weird voltage readings:
QE06
B = -18.55v
C = 18v, kind of wobbly. Should be -0.2v
E = -18.67
And on the diff amp QE04
B1 = jumps all around between 0 and 5v. Should be 0v
C1 = -18.77v
E = -10v, jumps around a lot. Should be 0.5v
C2 = -18.74v
E2 = -0.001v
I've replaced CE32, CE34, CE36, CE38, CE40, and QE06. I've tested all the resistors out of circuit and pulled QE04 and tested both sides with my transistor tester.
I'm out of ideas. What do you suggest? Schem attached
