left channel distortion

Discussion in 'Marantz Audio' started by Markojb, Aug 27, 2017.

  1. Markojb

    Markojb New Member

    Messages:
    9
    Ok guys, Ive seem to have hit a common problem with several of the receivers I am trying to get going again and for whatever reason ALL 3 have the same issue. The models are Marantz 2240, 2252b and a 2265b .
    The problem they have is that one channel is distorted when in stereo mode and the other channel there is no sound. When i click the mono button i get sound out of both speakers but the one channel is still very distorted while the other is nice and clear.
    I should mention that the 2265b was blowing fuses when i first got it so i replaced all the out put transistors and that stopped the fuses from blowing but now have this issues. I should also mention that i replaced the out put transistors in the other 2 as well just to see if that was the problem and that didn't do anything. I also have rebuilt the power board on the 2240 with all new capacitors. I have also cleaned all the pots on each of these units.
    Does it seem strange that all 3 of these receivers have the same ailment?
    With that said I turn it over to you guys for some advice on what to target on these to get them working properly.
     
  2. willyrover

    willyrover Super Member

    Messages:
    2,807
    Location:
    Hamilton
    Since you have changed all the output transistors, first thing I would do on all three units is figure out whether your amplifier sections are working properly or if the problem is in the preamp. Since pressing the MONO button gives you sound in both channels, it sounds like the amplifier modules could be fine. The distortion might be coming from the preamp.

    You can verify the operation of the amplifier section of each receiver by connecting a VOLUME CONTROLLED source (CD player with variable output, mp3 player, etc.) to the MAIN IN jacks. This connects directly to the amplifier module and you can verify if you're getting clear sound from both channels.

    From there, pick ONE unit to focus on at a time. (And stop changing random parts.)
     
    Last edited: Aug 27, 2017
  3. runningdog

    runningdog AK Subscriber Subscriber

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    Location:
    Sonoma, CA
    One explanation would be that your source or speakers are distorting the sound. You've probably ruled that out but a quick test is to reverse the left and right input connections and see if the distortion moves.

    One channel plays but is distorted, the other is silent. When you engage the Mono switch then you get sound out of both channels but the one is still distorted. This tells you that the main amplifier you hear only with Mono engaged may be OK and the problem is further upstream. And that the other amp may be an issue.

    Do the test on the Main In jacks as suggested by willyrover.

    Then use a pair of RCA cables to cross-connect your Pre Out jacks to your Main In jacks. So that the left Pre is going to the right Main. Note if the distorted channel switches sides.
     
  4. Markojb

    Markojb New Member

    Messages:
    9
    Since the 2252 was closest i did both these test. When puttimg an mp3 player though the main ins there was no change. Same distortion.
    When i did the sexond test of switching the sides the results were again the same with no change . The static didnt change sides.
    So i think that confirms its in the amp and not the pre . So ........what to attack now? A total rebuild of the amplifier board?
     
  5. Denten

    Denten Super Member

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    4,494
    Location:
    Ontario
    Speaker relay perhaps?
     
  6. willyrover

    willyrover Super Member

    Messages:
    2,807
    Location:
    Hamilton
    Could be the relay or the speaker selector switches.
    Clean the speaker switches again and work them really well. Repeat the test with the mp3 player to the MAIN IN and tap on the relay to see if anything changes. Also work the speaker switch in different positions to see if the sound cuts in and out.

    The relay is the black cube rear right of the board and the speaker switches are next to it.
    Screen Shot 2017-08-27 at 11.28.28 PM.png
     
  7. Markojb

    Markojb New Member

    Messages:
    9
     
  8. Markojb

    Markojb New Member

    Messages:
    9
    If i tap on the speaker relay i can get the sound to kick in and out, change volumes etc while i can get it to make sound out of both chanels the audio is not clean. Ive cleaned the snot out of those speaker switches with no change.
     
  9. Denten

    Denten Super Member

    Messages:
    4,494
    Location:
    Ontario

    You need a new relay, the audio is not clean because the contacts in the relay are dirty, you can confirm this by checking for clean signal before the relay.
     
  10. rBuckner

    rBuckner Luv 2 Restore Subscriber

    Messages:
    9,301
    Location:
    Prescott, Arizona
    ^^^ This! Don't attempt to just clean the relay contacts, get a new one as Denten suggests.
     
  11. Denten

    Denten Super Member

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    4,494
    Location:
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    Hi Randy, is it a bad idea to check for signal before the relay on all amps and receivers? I hate giving bad advice. It seemed like a good idea at the time......I've got a lot to learn. :)

    Edit: Sorry, Randy. I need to work on my reading comprehension skills. :oops:
     
    Last edited: Aug 28, 2017
  12. willyrover

    willyrover Super Member

    Messages:
    2,807
    Location:
    Hamilton
    I think he meant if the relay is found to be bad, replace it with a new one rather than try to clean it.
     
  13. Denten

    Denten Super Member

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    4,494
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    Oh, I get it now! I thought he meant don't attempt to check for clean signal before the relay. :thumbsup:
     
  14. rBuckner

    rBuckner Luv 2 Restore Subscriber

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    Location:
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    It WAS a good idea to check for good signal before the relay - well done! And yes to replacing it vs. cleaning it.
     
    Denten likes this.
  15. Markojb

    Markojb New Member

    Messages:
    9
    Well I got around to putting a new relay in 2 of the units. The 2265b is fixed and seems to be running and sounding fine. Unfortunately the new relay did not fix the 2252b as left channel is still very muddy and distorted. Any suggestions on what the next step would be with the 2252b? When a capacitor starts to lose its values is this ever a symptom of that?
    Thanks again guys. Will let you know if the new relay fixes the 2240 once i get that in.
     
  16. Denten

    Denten Super Member

    Messages:
    4,494
    Location:
    Ontario
    Try running the 2265b pre out to the 2252b main in, if the left channel is now clean, then the fault is in the 2252b's preamp, if the left channel is still muddy, then the fault is in the 2252's left amp.
    Also you can try running jumper cables from the 2252b's pre-out to it's main-in........this will help to rule out the internal connectors.
     
  17. Markojb

    Markojb New Member

    Messages:
    9
    I have already done that and can confirm that it is not in the preamp section as the affected channel doesn't change when supplied with a source on the main ins.
    Thanks Denten
     
  18. willyrover

    willyrover Super Member

    Messages:
    2,807
    Location:
    Hamilton
    If you have confirmed the fault is in the left channel amplifier you need to focus on on this area of the schematic. Confirm output transistors C711 and C713 test good.

    Screen Shot 2017-09-05 at 4.36.39 PM.png

    This area of the schematic corresponds to this area of the main board. Notice that ODD numbers correspond to LEFT channel components.

    Screen Shot 2017-09-05 at 4.39.01 PM.png

    Check all ODD numbered electrolytics from C701 to C729.

    Test all small transistors Q701 to Q719 (might be mislabelled Q718 in left channel)
     
  19. Markojb

    Markojb New Member

    Messages:
    9
    I have ordered some parts and we'll see what happens on the 2252b :)
    In the mean time I got the 2240 on the bench and unlike the others when i hooked up my ipod to the main ins, she sounded perfect. Strong and clear on both sides. When i switched it back to aux in, I got very faint sound on right channel and same ole static on the left. Not sure why it was so quite as that is a new symptom? So this sounds more like a preamp issue if im getting clear sound from the main ins and kahkah from the aux in? Anything popping out on where I should start on this one?
    Thanks for all your help so far!
     
  20. rBuckner

    rBuckner Luv 2 Restore Subscriber

    Messages:
    9,301
    Location:
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    Did you DeOxit D5 treat the pots and switches yet? Miracle in a can!
     

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