2245 & 2250B: Different sound quality left vs. right ouput. Recap time?

[jd3rdcoast]

Hi all;
Long time member and avid reader. I have two recently acquired receivers 2245 & 2250B. Have replaced lights as needed, set Voltage, DC Offset and Idle-current respectfully. I notice that both units have slightly different left vs. right sounding outputs to HD77 speakers. 2245: L channel sounds better. 2250B: R Channel sounds better. Curious if this is an indication that some other adjustments are needed or if this is indicative of a capacitor issue? Which ones? Power Supply? Amps? Outputs? Not a major difference, but enough when switching balance between left and right that I notice it and would like to attempt a remedy. I am capable of the repairs and upgrades as needed (except FM/AM tuning). Would like to hear some thoughts from this esteemed group I have always relied on as my go to source. Thanks;

 

[Steven Tate]

I'm not an expert, and I can't say if recapping would fix your problem or not, but I have recapped several 2245's and they always sound much better after doing it. At minimum, I would recap the power supply, tone board and power amps and replace the big filter caps (Nichicon Gold Tune 10,000 uF 80V caps are a great drop in here). It's possible your problem lies in a semiconductor somewhere, but I'll bet recapping those areas would eliminate your problem.
Steve

 

[catrafter]

I'm wondering if this could be a speaker or source issue. Have you tries swapping them left to right?

Tom

 

[jd3rdcoast]

I'm not an expert, and I can't say if recapping would fix your problem or not, but I have recapped several 2245's and they always sound much better after doing it. At minimum, I would recap the power supply, tone board and power amps and replace the big filter caps (Nichicon Gold Tune 10,000 uF 80V caps are a great drop in here). It's possible your problem lies in a semiconductor somewhere, but I'll bet recapping those areas would eliminate your problem.
Steve

Thanks Steven; On close inspection don't see any leaking caps. (All grey Elna's) (I know that is no guarantee they are not off spec). I noticed the main filter caps are Elna 9,0000 mF 55V. The manuals state 6,600 uF 55V. (2245 Serial number is 54295). Off this topic but curious if Marantz bumped these up at some point or if this unit has been recapped in the past.

 

[Steven Tate]

Thanks Steven; On close inspection don't see any leaking caps. (All grey Elna's) (I know that is no guarantee they are not off spec). I noticed the main filter caps are Elna 9,0000 mF 55V. The manuals state 6,600 uF 55V. (2245 Serial number is 54295). Off this topic but curious if Marantz bumped these up at some point or if this unit has been recapped in the past.

No, this substitution is just a very commonly recommended one by several of the experienced techs here on AK. You will find it on several parts lists for the 2245 and 2270. They generally say increasing the capacitance up to 50% may be helpful and won't generally hurt the system. Any more than that, and you may over stress the power switch and rectifier. But in this case, it's only about a 10% increase. The increase in voltage rating only refers to its maximum voltage rating. It's fine to use in a lower voltage circuit. Mainly, this is just a very high quality cap that happens to be the same physical size as the Elna 9000 uF caps.

 

[jd3rdcoast]

I'm wondering if this could be a speaker or source issue. Have you tries swapping them left to right?

Tom

Thanks Catrafter; I have thought the same thing and have swapped speakers, checked polarity etc. I had both the 2254 & 2250B stacked and was moving the speaker cables back and forth between the two units and noting each unit had slightly better quality sound out of the opposing speaker respectively (2254. I hope that made sense. So I am ruling out the speakers at this point.

 

[jd3rdcoast]

I was double checking the 2254 DC Offset and Idle Current. No problem with DC offset to 0 VDC. For Idle Current, the manual I have states
"Connect a DVM between J753 and J754 on the power amp board. Adjust R763 fully counter clock-wise and then turn clockwise adjusting for 5mVDC."
When I measure this voltage I am seeing 36 VDC between J753 & J754 on both P750 amp boards. Triple checked the connections and I am on the right ones. Wondering if I have an outdated manual for this unit?

This kind of threw me as had no problem with the 2250B.

 

[Steven Tate]

I think those instructions are for pre 3900 serial number units. For higher units, measure between J754 and J760 and set R763 to 10mV. This is discussed several times in the Marantz Service Manual Error thread - sometimes in the context of the 2270, which has basically the same amp design as the 2245.

 

[jd3rdcoast]

I think those instructions are for pre 3900 serial number units. For higher units, measure between J754 and J760 and set R763 to 10mV. This is discussed several times in the Marantz Service Manual Error thread - sometimes in the context of the 2270, which has basically the same amp design as the 2245.

Thanks! I suspected something like that, but was not sure where to look. Will update my manuals. That made sense as the schematic is correct. Measuring between 0 vdc side of both H001 & H002.