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Yamaha CA-1000 channel drop out volume after 10 mins.

Discussion in 'Yamaha' started by mgl99, Sep 10, 2018.

  1. mgl99

    mgl99 New Member

    Messages:
    12
    Hey guys,

    I purchased this nice amp about 2 years ago. It seemed to work fine. The previous owner had rebuilt most of the boards with Nichicon caps. What I have noticed now is that it will fire up fine, but after about 10 minutes, the left channel drops significantly in volume. The primary filter caps have not been replaced. I'm aware of the common fault of a coupling switch problem. I jumpered the preamp to amp RCAs with the coupling switch in the disconnect position. The same thing happens. My next step will be to criss cross the jumpers and see if it's the amp or preamp. Has anyone had this happen? If so, what would be a possible problem? The balance pot and all other pots have been cleaned with Deoxit. I'm not sure what to do to track down the problem. No, I don't have an oscilloscope. Any help would be appreciated.
     

     

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  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,711
    Location:
    Fort Dodge, Iowa
    Try tapping on the protect relay on the power supply board. Located on the underside of the amplifier.While listening for audible changes. Maybe fouled relay contacts.
     
    Last edited: Sep 10, 2018
    slimecity likes this.
  3. mgl99

    mgl99 New Member

    Messages:
    12
    Great idea. Thanks! If I get a response, I'll remove the relay cover and clean the contacts. One thing I forgot to say was that after the left channel volume drop occurs, it will intermittently regain the normal volume, and this would fit into the dirty protect relay contact theory. Thank you for the help. After I try it, I will report back on progress. With regard to the coupling switch issue a lot of people have had, is there a known recommended switch to replace the original one? If I'm going to go into this amp, I'd like to replace that switch since it has caused a lot of problems historically for other owners.
     
  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,711
    Location:
    Fort Dodge, Iowa
    It's the easiest slide switch in the amplifier to disassemble and clean.:thumbsup:
     
  5. mbz

    mbz Super Member

    Messages:
    2,177
    Location:
    Melbourne, Victoria
    OK to prove the theory but replace later with HC2-HP-DC12V-F.

    +1

    The CA-1000 is a real PITA to refurb but if done right is certainly worth the effort
     
  6. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,711
    Location:
    Fort Dodge, Iowa
    Last edited: Sep 29, 2018

     

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  7. mgl99

    mgl99 New Member

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    12
  8. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,711
    Location:
    Fort Dodge, Iowa
    Last edited: Sep 29, 2018
  9. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,711
    Location:
    Fort Dodge, Iowa
    Last edited: Sep 29, 2018
  10. mgl99

    mgl99 New Member

    Messages:
    12
    I had not considered this as a source of the problem I am experiencing. I will replace the relay and then decide to pursue any other culprit.

    Thanks,

    Mike
     
  11. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,711
    Location:
    Fort Dodge, Iowa
    This is more of preventative maintenance. If switching from Class A to normal with power applied it will pit/burn the snap action switches contacts. This little-publicized fact is not in the user manual. So .. These switches have a good chance of being damaged in used equipment. Maybe not to the point of failure yet...Just food for thought.
     

     

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  12. mgl99

    mgl99 New Member

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    12
    Thank you for the input. I am aware of this potential for damage. Fortunately, I have not experienced any problems, however, I took your advice and ordered the switches. Since I'm in there anyway, might as well replace them, right? Haven't received the protection relay yet, but I'm hoping that will repair the volume dropout problem. I have a nice Yamaha tuner that I need to dig out to go with it. It is possible that the previous owner had no interest in using the Class A portion of the amp and didn't do any switching at power.
     
  13. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,711
    Location:
    Fort Dodge, Iowa
    Anything is possible..
     

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