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Marantz 2325 Right Channel Troubleshooting

richardg0n

richardg0n

Active Member
Greetings AK Members,

Working on a 2325 restoration/recap and asking for your guidance. I have rebuilt/recapped the power supply P800, PE01 Pre amp, P400 Phono amp, PU01 Multipath, and PH01 Buffer amp board.

I have restored several 2325s, and this is the first time I am experiencing an issue with the right channel. I suspect the problem may be from installing the notorious cap at CH13 with the polarity reversed on PH01(buffer amp assembly). I installed a new cap at CH13 and replaced a smoked resistor at RH28.

Everything seemed to be working correctly, including The left and right channels. I then moved on to recapping the P700 right amp board. The trouble began once I completed the recap of the P700 right channel. There is no audio on the right.

Here are the steps I have taken so far to troubleshoot.

1. Crossed the pre and main RCA's in the back, and there is no output from the right main.

2. Removed output transistors from right amp P700 and tested with a multimeter in diode test mode. All four are working and in spec.

3. Used oscilloscope to trace the audio path through the pre-amp PE01, and there is a good signal going through and out of the pre-amp.

4. Verified there is power from J809 on P800(power supply) to the right amp.

5. Swapped out right side p700 from another 2325 and still experiencing the same issue.


How would you troubleshoot this? your input is much appreciated.
 
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How extensive was the re-cap you performed on the P700? Since it worked before the re-cap I would remove it and carefully inspect all of the components you replaced to ensure the polarity's are correct. Also conform that all the solder connections are solid and there are no "cold" solder connections. On the output transistors confirm that none of the wires connecting them to the circuit board were damaged by the flexing done while working on the board. I am assuming the output transistors were installed in the correct positions in that the fuse did not blow when you powered the 2325 up.

Good luck, I am sure you will find the issue when you closely inspect the P700 board.

Rich
 
SOLVED!!!

The problem was a bad solder at the rear right RCA main. I circled back to the buffer amp (PH01) and re-checked all the transistors and a few resistors and they all checked out to spec. Transistors and resistors on PH01 were resoldered and before powering up I decided to also test the RCA Main/PRE by plugging in and wiggling prior to powering up. The right channel returned! After a few minutes, I noticed the right channel dropped out again. I resoldered the RCA contacts on the Main Right and that was the fix. I’m learning how to be patient with troubleshooting, I’m learning to stop and walk away. I don’t know how many other AK’ers troubleshoot but for me patience is key.

By the way, I’m noticing many problems with RCA MAIN/PRE contacts on 2325’s.
 

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Check the two bias/dc offset wirewound pots on the Left P700 board. Clean them and then reset the bias/balance. The DC offset gave me problens with a crackling/popping sound on one unit. I ultimately replaced them.
 
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