Marantz 2285B right channel distortion.

DraKnight13

Active Member
Hello, I have a pretty decent Marantz 2285B from a guy. He said it wasn't working right.
Right now the condition of the receiver is it will receive input, play but the right channel will sound like bass distortion (like when you play volume too loud on the bass).
What I have done are:
  • cleaned all the switch and the pot (Deoxit, I did take faceplate off to access the pre-amp section)
  • took off the relay and clean it with a bit of deoxit and very fine sand paper and then reinstall it.
  • switched the speakers and input around and confirmed that it only stay on the right channel (both system).
Right now, when first turn on, there is a loud buzzing on the right channel, and then only left channel play. If I press the mono button (either left or right), the sound will come into the right channel, but still distorted. I plan on taking all the pot off the pre-amp section tomorrow for better cleaning (since kinda hard to get deoxit into them) and see if it help.
My question is am I on the right path? I think the problem is in the pre-amp board, and plan on dealing with it accordingly. I am new at this. I can solder fine, and can read schematic somewhat (slow). Thank you for any suggestions.
 
One more easy item to check. Clean the pre-main interconnect on the back panel. It is a lever type which can lose contact. Spray, insert RCA cable, and work the contacts.
 
I wouldn't! They're soldered now?! Yipes!!!!

First I'd check the power supply voltages for their correct DC voltage values and also check for AC voltage given the buzz on power on. That wouldn't explain the vast sound difference between the sides though.

I wonder if the loudness switch is stuck on for the bad channel. Try pressing the loudness button in and see if that makes both channels sound the same. Another experiment, if the preamp out to main jumpers aren't soldered in would be to cross patch them. By that I mean use a cable to connect the left preamp output to the right main amp inputs and vice versa for the other channel. If the bad channel remains, it's in the amp and if not, then anywhere before it like the preamp, tone control board or even a filter switch board problem.
 
I have update.
I did the cleaning (removed all pot from the pre-amp board and clean). I did not mess with the jumpers (tiny space with too many wires). That didn't help.
Now while sitting there being sad, I notice one of the big electrolytic cap have some dust on it, turn out it isn't. The cap is C004 (on the schematic) and seem to be damaged. Value is 6800 micro F x 2, 63V. I measure the cap in comparison with the other one, in diode mode it show an open line (which for my work, not a good thing). My question is what to replace it with? Also brand of cap matter plus do I have to replace both of them or just one is ok.
 
thanks, I found that and someone explained to me what to do, it was very helpful. My other question is while I'm at it, what else should I replace?????
 
In my opinion, just do the needed repair and get it working properly. Then you can decide if you want to dive into a recap/rebuild. That's quite a job on a 2285B. If it adjusts to spec and sounds great, you might consider leaving it as-is after the repair.
 
Thank you, I will replace both of those cap (save the old one of course) and deal with the rest later. The left side sound really really good so I think I should be fine. I hope I can tackle this. Thanks everyone for the advice!
 
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