Marantz 4100 right rear voltage help

[Butch Deal]

I have a 4100 that has been recapped and worked up about 15 years ago. Was acting up with a lot of static on the right rear channel. I pulled the preout to main in jumpers and still a lot of static on the right rear.
I marked and cleaned with deoxit the all 8 pots on the 600 boards. It is now showing ~4.5V on the right rear output
And about 6.5 V on J608 and 4.5V on J606
Nothing looks burned or blown with exam.

Could this be bad balance pot?
Any suggestions?
Thank you.

 

[eiraved]

Welcome back to AK, you've been gone for a while!
4.5V at the right speaker output? You should be reading between 0 - 50mV. Start by checking your output transistors.
Here's a thread with troubleshooting steps which may help:

Thread 'Marantz 4100 Right Rear channel noise'

Sep 7, 2021

Hey folks,

One of the channels for a Maratz 4100 quad that I'm recapping is making some noise.
I'm trying to troubleshoot and I isolated the problem to a section of the circuit...

This is a snippet of the P600 (right channel) schematics


The problem can be confirmed by measuring some transistor voltages:

H007 B: -31v, C: -11v (-0.01v), E: -31v
H610 B: -14v (-0.1) C: -14v (-0.5) E: 0.06v

R645 and R635 are not burnt but are showing overheating discoloration.

All other transistors of that section seem to be measuring nominal.
I have tested H621 and H625 off board and they...

• mgrisoli
• Replies: 9
• Forum: Marantz Audio