Marantz 4300 pre-amp problem PE01no sound

[daveyh]

Had the problem before and read some posts before I went to work on this. Seems like other people were having some problems with this also. Could not find answer. I recapped the PE01 Buffer and Pr-amplifier board and PD01 tone with new caps and all new transistors and still get no sound passed the HE06-HE12 (2sc720 and 2sc1318) transistors. It did nothing to help the problem I was having. Distortion only from 2sc720 and 2sc1318 transistors. Then completely dead going down board. Need help. What next?

 

[Robisme]

2SA720.

Have you checked the voltages at those transistors?

Rob

 

[daveyh]

2SA720.

Have you checked the voltages at those transistors?

Rob

If I measure DC voltage I get no reading on emitter or base but get around .14v on collectors. If I check AC volts I get about half of what the schematics calls for.

If you are looking for? AC voltages I can measure them HE05-HE08 and post.

Thanks

 

[daveyh]

When I rebuilt the power supply I checked the fuse on the power supply P800 board. It checked good. But after you mentioned to check the voltages I checked the voltages on the PM01 board and there was none. So I traced the JM04 which is a yellow and brown wire back to the P800 plug on the board. Pulled the fuse and checked it again. It was open. Maybe just old and from flipping the unit over and over. I put a new one in and she powered on! I have sound. Sweet. Now just need recapped some other boards and some minor restore like new lamps and some clean up.

Thanks for steering me on the right path. :thmbsp:

 

[Leicalover]

Hi,

not really sure, what you mean with your problem, is it on all four channels? But I would first check all four VD1212's on this board. They very often go bad, I had problems with these on 4300 and same 4400 board.....but would affect one or two, and not all four channels at the same time.
Better to replace them with two 1N4148 in serie, each.

 

[daveyh]

Hi,

not really sure, what you mean with your problem, is it on all four channels? But I would first check all four VD1212's on this board. They very often go bad, I had problems with these on 4300 and same 4400 board.....but would affect one or two, and not all four channels at the same time.
Better to replace them with two 1N4148 in serie, each.

I already replaced the all four diodes when I rebuilt the pre-amp board. In my above post you will see I got it working.

I do have another problem I would like to solve. I can set the audio adjustment as referred to on page 11 # 20 on J036 of the SM on the left side to 12mV DC but the right will not adjust that far down. The right side reads 28mV DC. I changed out the trimmer resistor to another one from a parts board but that did not help. All other adjustments are fine. Any idea how to bring it down the right side to the correct voltage?