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C2a volume fade in one channel

Discussion in 'Yamaha' started by jdsalinger, Aug 11, 2018.

  1. jdsalinger

    jdsalinger AK Subscriber Subscriber

    Messages:
    876
    Location:
    KCMO
    I have thoroughly de-oxited switches and pots and replaced all electrolytics.

    Once in a while though, the RH channel will drop out temporarily and last night it kind of faded out slowly. But then the channel popped back after 15 sec or so.

    It seems to happen when the amp is first started up and then gets better after warm-up, but it hasn't happened enough to say for sure and once I just disconnected it and went through the M2 directly from my DAC. So I know it's not the M2.

    I realize this is a complex preamp and it could be anything. But just wanted to ask before I dig in. Is this perhaps a common issues with Yamaha preamps? Is there a recommended faulty transistor or relay that I should have replaced in addition to the recap?

    I don't think I experienced this before the recap, but I didn't have it long before recapping either.

    TIA !
     

     

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  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,761
    Location:
    Fort Dodge, Iowa
    This problem could be ...
    1. A cold solder connection in the R-channel signal path.
    2. A faulty transistor in the R-channel signal path. ( breaking down as the component heats up)

    It may be a tough problem to locate. Due to it being so intermittent.
     
  3. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,761
    Location:
    Fort Dodge, Iowa
    What source were you using when the last episode occurred?
     
  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,761
    Location:
    Fort Dodge, Iowa
    Have you eliminated the possibility of the source or the power amplifier being the problem?
     
  5. jdsalinger

    jdsalinger AK Subscriber Subscriber

    Messages:
    876
    Location:
    KCMO
    Streaming Spotify through a new Topping DAC. Aux input.

    Yes, First time I noticed it, I took the C2a out of the system and went directly into the M2 from the Chromecast Audio. No more issues.
    That time, the channel had some soft popping, squealing sound too if I remember correctly.

    I seem to recall that there are many "Another thread about crackling and popping". Maybe it's my turn. I will search for those threads and see if I can narrow it down.
     
    milo63 likes this.
  6. jdsalinger

    jdsalinger AK Subscriber Subscriber

    Messages:
    876
    Location:
    KCMO
    I looked really hard for any cracked solder joints when I did the recap. Everything looked really good. But looks can be deceiving.
    I'm kinda glad it's in the C2a and not the M2 cause it should be easier to work on and diagnose.
     

     

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