1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

Restore + Repair Yamaha C-2a & C-80 / M-80

Discussion in 'Yamaha' started by mr.muddles, Aug 25, 2018.

  1. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    TR05
    D = +4.2V
    G = 0mv
    S = + 822mV
    /
    S = +850mV
    D = 0mV
    G = +4.1V

    TR06
    D = +3.26V
    G = 0mV
    S = + 550mV
    /
    S = + 528mV
    D = 0mV
    G = +3.24V

    I guess these look okay...
     

     

    Please register to disable this ad.

  2. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    I started cleaning it up... previously I diode tested all the jumpers to make sure they were still good
     
  3. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,802
    Location:
    Fort Dodge, Iowa
    I'm pretty busy today. I probably won't be much help. Possibly Patrice will pop in. The Right channel was working OK, wasn't it?
     
  4. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    From what I can see the voltages seem to be within spec until we hit TR14 and TR12
     
  5. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,802
    Location:
    Fort Dodge, Iowa
    Right channel
     
  6. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    I have not tried to listen to it since the onset of new problems... but yes, the original symptoms was that the right channel would drop in stereo but both channels had sound in mono. I'm pretty sure I don't have sound in either channel right now though?

    No worries about helping today. I'm just posting the readings so it's available and I had some time this morning. I have some other things I can work on. Thanks for your help yesterday.
     

     

    Please register to disable this ad.

  7. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    If these are the right channel then maybe that's what the problem is...

    to clarify... the original problem channel was the right channel. the left channel was working.
     
  8. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,802
    Location:
    Fort Dodge, Iowa
    Left channel still OK ?
     
  9. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    I still have TR527-530 out of circuit... I was waiting for @clinic-audio to look at the voltage readings...I'm not sure if the left channel is still working...

    before when 527-530 was in circuit there was smoke and resistors were burning so I'm not going to put them back in until someone says to do so or I have a good reason to put them back in...
     
  10. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    2,182
    Location:
    France
    Will come in 2 hours
     
    mr.muddles likes this.
  11. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    2,182
    Location:
    France
    I am back

    can you check the deleted transistors ?

    As Dave asked , is left channel working ?
     

     

    Please register to disable this ad.

  12. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    Hey Patrice, welcome. Thank you for your help.

    How do you want me to test the transistors? out of circuit with a diode test?

    If I put them back in I am afraid things will start smoking...
     
  13. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    one transistor is shorted for sure...
     
  14. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    TR529 / 2SA9130 is shorted or open
     
  15. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    the other ones measure good i think but the pin out does not match the legend on the schematic
     

    Attached Files:

  16. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    USING DIODE TEST:

    red/+ on B

    C = .0035
    E = .0029

    black/- on B

    C = .0035
    E = .0029
     

    Attached Files:

     

    Please register to disable this ad.

  17. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    Do you want me to put one pair of good transistors back in one channel?
     
  18. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    I'm not sure about TR530..

    red/+ on B

    C = OL
    E .5879

    black/- on B

    C = OL
    E = OL

    Is it shorted between the base and collector?
     
  19. mr.muddles

    mr.muddles Active Member

    Messages:
    458
    Location:
    Portland, OR
    I think I was just confused about NPN/PNP on the schematic legend earlier...
     
  20. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    2,182
    Location:
    France
    what you wrote is correct ( BCE) but the drawing in the square is wrong ! is it coming from original SM ??
     

Share This Page