Marantz 2238B, Not equal output R,L.

[Robisme]

Picked up a Marantz 2238B today for my Marantz collecting buddy. It was dirty but in good condition. the seller said it works.
Well, it does work, just not well. The right channel is much weaker than the left. I opened her up and cleaned all the controls, no change. Connected the pre out of the 2238B to the main in on my Nikko 7070. Same problem. I then connected the pre out of the Nikko to the main in of the 2238B, bingo, equal levels. This means the problem is with the pre-amp section of the 2238B.
Any ideas?

Thanks.
Rob

 

[Robisme]

Here's a pic.

 

[SB Marantz]

Are you shure the controls are cleaned good?
Tape monitor switches may cause this problem and also speaker switches.
When you done this allready then follow step two

Is the much weaker channel producing a hum?
Just recap the whole pre-amp section and take out the transistors and messure them on hfe and/or shorted.

Also check diodes, resistors and bad soldering's

It is allso a whise thing to recap the power section allso while your at it!

 

[Robisme]

Is the much weaker channel producing a hum?

Ni hum. If I adjust the balance to equalize the channels, I can turn it up and it sounds fine.

I will start by tracing the signal and see if I find anything. If not, I'll go your route.

Thanks.

Rob

 

[Avocado Dream]

I have a service manual Robisme, PM if you need it.

-Dave

 

[Robisme]

Volume Pot??

I dismantled the receiver to get the pre-amp/tone board out, but still have it operate. I traced the signal to the volume pot. It is equal on both inputs but lower on the right output than the left. The more I turn up the volume the more it seems to equalize. Speakers are off, of course.

I have cleaned the heck out out of the pot. Could something further down the line in the circuit be pulling it down? Or could the volume pot be bad?
I have not seen a bad volume pot before. Is this a common failure?
I guess I have to pull it to test it. Oh well. I'll get to it.

Thanks

Rob

 

[Robisme]

I pulled the volume pot, which is a dual pot, and tested it with a meter.
As I turn it clockwise, when one side was 42.0k ohms, the other was 42.4k ohms. I guess 400 ohms makes a difference. So I put it in a vise and turned the top pot with pliers just a bit until they were equal. I reinstalled it and now both channels are equal. I thought for sure it was going to be a cap or transistor. I feel some of you cringing as you read this, but I was very carefull and it did not loosen it up.

Hey, it's going in my buddies boat storage building. It will be fine.

Now I need but one fuse lamp and I can button it up.

Thanks AD for the service manual, it helped alot.

Rob