Marantz 2238b No bass/mids on Right Channel

[RMilton]

I recently acquired a very clean Marantz 2238b. It was recapped a few years ago, cleaned, and the bulbs were swapped with LEDs. The work was performed at a professional shop here in the midwest (at the request of the prior owner).

The left channel works perfectly. The right channel has great treble frequencies (same as the left channel), but no bass at all. At normal volumes it's hard to distinguish the issue if you aren't listening for it, but when you pan to the right side it becomes clear that the right channel isn't emitting any lower-mids or bass frequencies at all. I've performed several checks, but I was hoping to get some guidance on next steps before tearing things apart or taking it in.

Tests I performed (none yielded any results):

• swapping speakers (duh)
• cleaned the POTS (balance, bass, treble, volume, etc)
• running through the "B" speaker zone
• using this 2238b as a "pre-amp" (both power amps I tested carry this right channel error forward)
• using this 2238b as a "power amp (I connected another marantz to the main-ins on this unit and still had the same issue)

So it seems this issue carries through both the preamp and power amp stages of the unit, and nothing I've tried has rectified anything.

Any tips on next steps? Thanks all!

 

[Magnus Back]

Maybe a capacitor or resistor has gone bad changing the high pass filter cutoff frequency on the P700 board?
One of C701, C702, R703, R704 perhaps?

 

[dr*audio]

The only thing I can think of that would cause this problem in both the power amp and preamp is a bad ground somewhere.

 

[Stromcek]

The left channel works perfectly. The right channel has great treble frequencies (same as the left channel), but no bass at all. At normal volumes it's hard to distinguish the issue if you aren't listening for it, but when you pan to the right side it becomes clear that the right channel isn't emitting any lower-mids or bass frequencies at all.

Interesting. Unfortunately, I have no useful information for you, but I do own a 2235B which has a channel imbalance problem that sounds quite similar to what you're describing. The right channel sounds brighter/more trebly with diminished bass, while the left channel sounds bassier. But one difference with mine is that the left channel also seems to be lacking in treble. It's kind of subtle, but more easily noticeable with headphones.

(It's also more noticeable with certain recordings, e.g., if you've got a mix with some bright, prominent acoustic guitar or a well-defined high-hat panned hard right, the brighter nature of the right channel will emphasize things like that more, making the stereo mix seem even more lopsided.)

At first I thought it was the cartridge, or some issue with my turntable, but then I realized I was hearing it with the CD player too.

At any rate, I'll be curious to see if/how you resolve the problem.