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Help. Issue with a CR 2020

Discussion in 'Yamaha' started by serioushifi, Mar 11, 2014.

  1. serioushifi

    serioushifi AK Subscriber Subscriber

    Messages:
    20
    I have a new to me CR 2020, mint cosmetic condition, worked fine until yesterday. I am having a problem with (don't know the correct name of the part) the relay or circuit breaker or whatever it is, that when powering up, delays the sound to the speakers for a few seconds.
    On a cold power up, instead of clicking (engaging) in a few seconds, it starts buzzing for twenty or thirty seconds, then sometimes clicks and everything is fine. Sometimes it does not click and I have to power it off and on several times before it clicks. After it has been playing for a while, I can shut it off and turn it back on and it seems to work fine, but from a cold start it rarely works correctly the first time.
    Any ideas what is causing this problem? What can I do to fix it?
    Thanks
     

     

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  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,685
    Location:
    Fort Dodge, Iowa
    Either a bad cap in the protect circuit or the 12 volt power supply or a flaky relay driver transistor or bad solder connection in those circuits.
     
  3. clearsoft

    clearsoft New Member

    Messages:
    9
    I had a similar issue with my CR-1020. Many many hours of troubleshooting, so wanted to share here in the hopes of saving others some heartburn.

    After a full power supply recap (both pcbs) and power transistor upgrade to higher voltage TIP31C in the supply, the protection relay would not fire. The -25V output sat at -10V. Cleaned the flux and grime off the bottom side the PCB and the output went to +6V. Disconnected the two purple wires from the -25V post to eliminate loading. No improvement. Removed and retested all 4 transistors; junctions not shorted nor open.

    Decided to look at the .01uF capacitors. In circuit across the terminals, the one on the -25V supply measured 6 kOhms whereas the one in the +25V supply measured 3 megohms. Pulled the caps; neither was leaky. Pulled the 4 transistors again. Still 6 KOhms...strange.

    Used flux remover to clean the top side of the PCB around the .01uF cap locations, removing glue residue around the heatsinks. Resistance now 2 megohms. Apparently the glue that Yamaha used was not electrically benign and the -25V supply is extra sensitive to leakage current (check out the circuit topology).

    Reinstalled all components. Reconnected all wires. Voltages perfect. Relay works.
    —Ed
     

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