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Yamaha CR-1020 Relay Issue

Discussion in 'Yamaha' started by Bluhn321, Mar 5, 2016.

  1. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
    Oshkosh, Wisconsin
    Hello all,

    I have a Yamaha cr-1020 that has a problem that I just can't figure out. So the main issue is that the protection replay won't click on and therefore no sound. I have replaced the relay but without success. It does power up fine and nothing blows up. Any tips on what to check next?

    Thanks!
     

     

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  2. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    2,180
    Location:
    France
    Hello Bluhn321

    It is the first thing to do if your relay is not actived . Do you have DC offset (or worse DC voltage ) at the output of each power output PCB between tag O and E ?
    Take a look on my drawing if you don't know where to look
     

    Attached Files:

  3. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
    Oshkosh, Wisconsin
    Alright so I did find a problem. The right board had a measurement of about 5mv but the left board had almost 50v!
     
  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,685
    Location:
    Fort Dodge, Iowa
    Most likely a shorted output transistor in that amplifier assembly.
     
  5. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
    Oshkosh, Wisconsin
    Well I checked the two output transistors and they both seem to be working fine. Just used my multimeter to check them so not sure if that would give a 100% correct conclusion.
     
  6. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,867
    Location:
    uk.. the middle bit
    check the rail fuses for the bad channel . one could be blown .
    f601
    f602
     

     

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  7. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    2,180
    Location:
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    Yourv relay will not work if you have 50V DC . This is the power transistor voltage , so one should be bad (E and C in short circuit )
     
  8. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
    Oshkosh, Wisconsin
    Checked the fuses and they check out good.

    Hm, well it makes sense. Just to be sure one is PNP and the other is NPN?
     
  9. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    Location:
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    yes . one NPN 2sd424 one PNP . 2sb544 have you got the schematic yet ?
     
  10. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
    Oshkosh, Wisconsin
    Alright. I have it but haven't it really looked through it yet.
     
  11. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,867
    Location:
    uk.. the middle bit
    you could check the voltages on the outputs cases to see if that could be the problem .cases are collectors . base and emitter are the pins . see how they are offset . bases should be about 0.6v + or - . emitters near 0v .
    [​IMG]
     

     

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  12. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
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    Yep checked it and it checks out good again. Even though they seem to be OK I'm thinking of replacing them anyways.
     
  13. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,685
    Location:
    Fort Dodge, Iowa
    Absolutely sure you were on the correct test point ? If so, then you have a issue somewhere on that amp assy. thats holding and output transistor at rail voltage.Could be anything in the front end of that amplifier including cold solder connections.
     
  14. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
    Oshkosh, Wisconsin
    I checked the two points shown in the picture.

    That's what I was thinking. I'll have a look at schematic and see what could have went wrong.
     

    Attached Files:

  15. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    now try black meter probe on bare chassis and red on the transistor cases one by one and see what their voltages are ..noting whether positive or negative .
     
  16. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
    Oshkosh, Wisconsin
    Alright so I got that transistor 2sb544 had -50.5v DC and the other had 50.5v DC
     

     

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  17. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    now see if you can get the base and emitter voltages .
     
  18. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,685
    Location:
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    Yep. Thems the ones.
     
  19. Bluhn321

    Bluhn321 Hockey: Making dentists rich since 1875 Subscriber

    Messages:
    233
    Location:
    Oshkosh, Wisconsin
    I got -45mv DC for transistor 2sb544 and -60v DC for transistor 2sd424
     
  20. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,867
    Location:
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    base or emitter ?
    i did forget to say it is important to post the exact voltages . no rounding up or down .
     

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