Marantz 2245 Left Channel Imbalance

[JDPossible]

Marantz 2245 with the left channel showing slightly less amplitude over the right. I've isolated it to the pre-amp/front end. Sign wave taken at the pre outs.

1k test tone used.

I've tried every input with exacting results
Thoroughly cleaned the selector switch with contact cleaner.

H406 & H408 shows voltages way off. Replaced with KSA992 & KSC1815. No effect on the issue.

I inspected for solder bridges on the P400 board and it looks great.

Checked all resistors on the P600 board. Disassembled the Loudness, Muting, Low Filter & High Filter buttons, cleaned, lubricated and used red Deoxit on the contacts.

 

[dankik]

Sign wave taken at the pre outs.

Why are your two channels (L & R) out of phase by 180 degrees?

 

[JDPossible]

Why are your two channels (L & R) out of phase by 180 degrees?

They aren’t. That is a scope setting for one of the channels. Makes it a little easier to visually see the difference.

 

[dankik]

What voltage to you have at J802 (35V) and J404? If that voltage is high your measured voltages H405, H406, H407, H408 will be high.
Check to make sure that resistor R012 is indeed 1k Ohm.

 

[Warren-Oates]

It looks like a small difference, did you measure the volume pot resistance? I have seen many pots that have a small difference and need a balance knob twiddle. Your work looks very neat.

 

[JDPossible]

It looks like a small difference, did you measure the volume pot resistance? I have seen many pots that have a small difference and need a balance knob twiddle. Your work looks very neat.

I replaced the volume pot thinking that was the cause. No cigar. Thank you.

 

[JDPossible]

What voltage to you have at J802 (35V) and J404? If that voltage is high your measured voltages H405, H406, H407, H408 will be high.
Check to make sure that resistor R012 is indeed 1k Ohm.

I got a different project on the bench (2240B). When I circle back around to the 2245, I'll check your suggestions and report back. Thanks.

 

[eiraved]

I got a different project on the bench (2240B). When I circle back around to the 2245, I'll check your suggestions and report back. Thanks.

You're pretty new around these parts, my recommendation is to strike when the iron is hot. AK member dankirk is sharp and is here now. Who knows if he'll be available to assist when you come back around to the 2245.