CA-1010 Right Channel Distortion

Discussion in 'Yamaha' started by mobiusfun, Jan 11, 2018.

  1. mobiusfun

    mobiusfun New Member

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    First of all, hi AK. I'm new to the forum and to vintage audio in general, but I'm happy to be a part of it.

    I recently acquired a Yamaha CA-1010 in not bad but not perfect shape. The only obvious issue I've been having with it is a persistent scratchy / static-y distortion coming from the right channel. This happens at all volumes, through speakers or headphones, and always in the right channel regardless of whether I select mono, stereo, or stereo reverse on the mode dial. It'll occur whether or not there is an input source, although I will still receive sound through the right channel with an input source.

    My first thought was a dirty switch or bad contact somewhere. Doing some research on these forums I identified the mode selector switch, muting switch, coupler switch, and speaker protection relay as possible culprits. That or bad / cold solder joints.

    I hit all the switches and pots / VRs with contact cleaner (just CRC; Deoxit's in the mail) and disassembled and cleaned the mode dial with contact cleaner and a hi-polymer eraser, to no effect. Next I disassembled and cleaned the coupler switch and re-soldered all the connections on the coupler control board. That actually seemed to make the problem worse, with the static now being considerably louder than it was before. I haven't done anything to the relay other than bang on it with a screwdriver a couple of times. It didn't seem to do much.

    Anyway I'm feeling somewhat defeated at this point, so I thought it was time to try my luck on these forums. Does anybody here more experienced than I am have any ideas about what could be causing this distortion?
     
  2. avionic

    avionic " Black Knights " Subscriber

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    Welcome to AK..
     
  3. avionic

    avionic " Black Knights " Subscriber

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    If you have a seperate amplifier or pre-amplifier. Seperate the pre-amp from the power amplifier of the 1010 with the coupler switch. Then using either and amplifier or preamplifier connected to the pre-out/main-in jacks.Doing this will eliminate major sections of the 1010. This way we can determine where to start looking for your issue.
     
  4. mobiusfun

    mobiusfun New Member

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    Thanks avionic. Using the CA-1010 pre-amp section and another JVC AV receiver I have, I was able to get clear audio. When I tried the reverse, using the JVC as a pre-amp and the power-amp section of the Yamaha, I got very scratchy and barely audible audio. I think some of that had to do with my imperfect re-soldering of the cup terminals on the coupler board. Still, it seems like the pre-amp section works fine.
     
  5. mbz

    mbz AK Subscriber Subscriber

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    Maybe resistance check the fusible resistors in the power amp section, in circuit ok with amp powered off/unplugged
     
  6. mbz

    mbz AK Subscriber Subscriber

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    Possibly check bias and dc offset it affected channel. These wont be the cause but are easily measured and may point to a problem area.
     
  7. avionic

    avionic " Black Knights " Subscriber

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    The protect relay contacts on the power supply board is a suspect. While the amplifier is running and acting up.Tap on the protect relay. Note if it has any positive or negative influence on the sound quality.

    The relay visible from the top of the amplifier is for class A operation and not the protect relay. The protect relay is located on the underside of the amplifier on the power supply board.
     
  8. avionic

    avionic " Black Knights " Subscriber

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    If you haven't already. Give the speaker selection switch a good cleaning. It too, is a possible suspect.
     
  9. avionic

    avionic " Black Knights " Subscriber

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    Also plug in a set of headphones and see if you have distortion through them as well.
     
  10. avionic

    avionic " Black Knights " Subscriber

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    This bypasses the speaker switch.
     
  11. avionic

    avionic " Black Knights " Subscriber

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  12. mobiusfun

    mobiusfun New Member

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    Thanks for the advice everyone.

    mbz, I'll check the fusible resistors and the DC offset tomorrow and report back with what I find.

    avionic, no change in audio quality after tapping the bottom speaker relay. Thanks for linking a replacement - I'll order a new one rather than trying to clean the existing relay and see if that helps any. Also, distortion is the same with speakers or with headphones. Actually, most of the testing I've done so far has been using headphones to avoid putting any of my speakers through anything this gnarly.
     
  13. avionic

    avionic " Black Knights " Subscriber

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    Bias ( idle current ) should be checked as well. It can be adjusted. The DC offset on the main amplifiers can not be easily adjusted on this model.
     

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