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CR-2020 trying to get up and running

Discussion in 'Yamaha' started by vinyl fiend, Apr 24, 2016.

  1. vinyl fiend

    vinyl fiend Active Member

    Messages:
    410
    Location:
    Newburgh, NY
    I have a CR-2020. When I lift the relay a little bit to a certain position, it clicks on and seems to work fine. Not sure if the board is warped or if it's a power issue. How do I check DC before the relay? Also, I haven't done the service upgrades. Is this correct? : Any suggestions are much appreciated.

    (2) 33ohm 3 1/4 watt ohmites
    (2) 22 ohm 3 1/4 watt ohmites
    (2) 2SD525 transistors
     

     

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  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,685
    Location:
    Fort Dodge, Iowa
    I'd be looking for cold solder connections on that power supply board. Especially under those heatsink mounted TO-220 transistors leads.(2SD525 transistors)
     
    Last edited: Apr 24, 2016
  3. Electone

    Electone Well-Known Member

    Messages:
    747
    Location:
    London, Ontario, Canada
    That whole board is constantly being cooked. Best to completely remove it and as Avionic said, check all solder joints. Be careful when lifting it - the connected wires will be brittle and can snap off. Ask me how i know...:oops:.
     
  4. HypnoToad

    HypnoToad Ms Puss Puss Subscriber

    Messages:
    6,046
    Location:
    Melbourne, Australia
    I had relay clicking in and out problems on my CR1020, I recapped the PSU board, the one with the relay and once I removed the fuse and put it back in, it all worked fine, I also replaced the heat sinked transistors with modern counterparts as if I tapped on them lightly the relay would click out and in. It hasn't missed a beat since. Check all the solder joints like Avionic said and also the connector between the PSU board and the Capacitor board as well.
     
  5. 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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