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Marantz 2230 stereo/mono button issue

N

noctech

New Member
Hello all - I know this issue has popped up several times before but I cannot find anything that suggests any possible fix action beyond cleaning it. My Marantz 2230 works on both channels when the stereo/mono button is on mono, left channel is extremely weak and noisy when stereo is chosen. This is on all inputs.

I have cleaned it as much as I can without disassembling it, any other thoughts?
 
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Welcome to AK! It's good news that it works in both speakers when set to Mono. This shows that the main amplifiers are both working. But the left channel is not working before the main amplifiers. This would include the preamplifier and specific controls.

As a first test, leave the switch on Stereo and play a tune through it. Cycle every button and knob on your 2230 30-40 times, gently. If it is corroded contacts on one of these controls causing the weak channel then it will turn up in this way.
 
Thank you for the suggestion, I had already cleaned the usual suspects like the tape monitor and input selector along with everything else to no avail. I just checked it again with the same result.
 
You have isolated the issue as being somewhere between the inputs and the Pre Out jacks. Because none of the controls showed issues when cycled, for now you can assume the signal is reaching the inputs of the tone/preamplifier board. Up to that point the signal has gone only through switches and pots, no electronics. You can test to make sure the signal is reaching both the preamp inputs with a signal generator and a scope. Or even an ohmmeter with the receiver powered off.

The power supply board can be ruled out as an issue. This is because only the left channel is being affected. If a component on the power supply board was failing it would affect both channels.

At this point I would be testing the outputs of the tone/preamp to see if the signal is not getting through the left channel there. It's not uncommon for a transistor to fail on this board, particularly the H401/H402 ones, and the symptoms would be like you describe. Again a signal generator and a scope is how I'd test this.

If it is on this board, it's possible a rebuild that includes all the transistors would resolve the issue. Not a certainty, but a rebuilt tone/preamp is a good thing anyway.
 
Not only does the issue still exist after rebuilding the tone board as suggested but the left channel now doesn't work at all in stereo and both channels are out in mono.
 
I just now ran across this tip -
. The long screws used to attach the feet when a cabinet is used can short out a channel in the dubbing inputs when the cabinet has been removed, which is how I got this unit. I pulled the feet and now have a strong right channel in both stereo and mono with a very low volume on the left for both.

I replaced the 3 caps on the top, all of the small white caps were pulled and reinstalled after testing good. All transistors were replaced as well, pic attached.
 

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I would suggest NOT pulling this board out of the unit when changing components. They can be accessed while still in the unit. Change one component at a time. Use a dim bulb tester and turn on after changing the component and hear/see the result.
 
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