2220B Weak & Distorted Left Channel - Bad Balance Slider?

[Catonawave]

Hey All,

I have a Marantz 2220B on my bench that had a noticably weak left channel which lacked bass and alot of volume compared to the right channel. Went ahead and cleaned controls, even flushed some of the dirtiest of them out with CRC QD, then De-Oxit in their respective places. I was still having issues with the left channel. I hooked it up to a signal generator and followed the signal from the Aux input jacks to the input of the tone board. I found that the left signal was weaker before it even enters the tone control board. I moved to the balance slider, on this model there is a Red and Brown cable coming from the speaker selector, which to my understanding, is where the audio enters the slider. and then a black cable where the signal moves to the volume control. When measuring the signal on the brown and red cables I found no discrepencies between the two. But when measuring the signal on the volume control the two channels are uneven (even after cleaning has been done). Any help would be appreciated.

Ive attatched an Image of the slider showing the input wires and the black wire running to the volume control.

 

[kwayde]

Try cleaning balance control like this:

Marantz 2010 Balance Slide Replacement Help!

 

[ivandezande]

Could always jumper/bypass it to see.

 

[Catonawave]

Try cleaning balance control like this:

Marantz 2010 Balance Slide Replacement Help

I've opened up the slider, wiping the metal rails and gently wiping the resistive fader sections. While it was dirty, it made little to no difference for the balance control. The left channel is still lower than the right. Attaching some pictures of the innards of the fader and the waves on the scope. Ive checked the inputs and the balance is even there, all the way until it reaches the slider.

Correct me if im wrong, but the slider would have some resistance when It's set in the center position, right? If I can find a resistor equal to that value, I can take the fader out of circuit and just replace it with the two resistors.

 

[kwayde]

You're sayin the signals are equal at the green arrows but not equal at the red arrows.

You weren't measuring the volume pot at the purple arrows, were you? That would mean the volume pot is possibly the problem.

The balance resistive pads look good. You could measure the resistance of each channel on the balance slider to see what the difference is.

If the balance control is bad you could just bypass it, no need to put resistors in it's place. When the balance is put all the way to one channel there should be no resistance.

 

[Soundork]

Long shot but...I once had the same problem and cleaning (several times) the tape monitor switch solved the problem.

Best

Soundork

 

[dankik]

I moved to the balance slider, on this model there is a Red and Brown cable coming from the speaker selector, which to my understanding, is where the audio enters the slider.

Looking at the schematic, the speaker selector switches are driven from the outputs of the P700 Main Amp board, not from the speaker selector to the balance slider.
The signal to the balance control comes from the PH01 Filter board Mono Switch which then comes from the selector rotary switch or Tape Monitor switches.
Please check your wiring.

 

[Catonawave]

I finally got a chance to sit down with this thing and tear into it again. thank you dankik for correcting me, yes the balance slider recieves it signal from PH01. I've probed and also measured voltage across the slider. Theres atleast a 10mv difference between the two channels when measuring the output of the slider (while it's sitting in the center position). When you measure the signal entering into the slider, its 17mv equal, the O-scope reflects this, as both channels appear even. I've sprayed and tore into it to clean the slider multiple times now. The only way to make the two channels even is to have the slider ever so slightly shifted to the left. Could this truly be a balance control gone bad? When I get another chance ill open it, I suppose I could measure the resistance of each channel. The customer states this has been a problem as long as he's owned it, since atleast the early 2000s.