Yamaha C-60 Woofer Pumping Problem

Discussion in 'Yamaha' started by kermit_xc, Apr 10, 2018.

  1. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Thats not even close. Should have been - 28vdc and +28vdc ballpark..
     

     

    Please register to disable this ad.

  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Are you grounding your neg test lead to "E" copper bus. And probing with the pos test lead to each end of the two resistors Should have +/- 27-28 volts on either end of each resistor.
     
  3. kermit_xc

    kermit_xc Member

    Messages:
    84
    Location:
    Austin, TX
    alright - correction (you are a true scholar and a GENTLEMAN!)

    R275 28.91V DC
    R276 31.75V DC
     
  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Now select AC voltage on your meter and measure the AC voltage on the two red wires coming from the transformer each wire should be 23vac.
     
  5. kermit_xc

    kermit_xc Member

    Messages:
    84
    Location:
    Austin, TX
    Both read 24.83V AC
     
  6. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Go back to DC voltage. I need to know the base and emitter voltages of TR149 and TR150.
     
  7. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
  8. kermit_xc

    kermit_xc Member

    Messages:
    84
    Location:
    Austin, TX
    T149 Vbe: 1.246V, Veb: 1.211V
    T150 Vbe: 1.306V, Veb: 1.327V
     
  9. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    No.....
     

     

    Please register to disable this ad.

  10. kermit_xc

    kermit_xc Member

    Messages:
    84
    Location:
    Austin, TX
    T149 E: 19.21V B: 20.5V
    T150 E: 9.78V B: 9.30V
     
  11. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Bingo...
     
  12. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Do you have +/- 12vdc on pin 1 and pin 5 of IC107 ?
     
  13. kermit_xc

    kermit_xc Member

    Messages:
    84
    Location:
    Austin, TX
    I think so :) the ultimate source of my -B1 readings?
     
  14. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Are you sure you replaced with a 4.7KΩ resistor for R271 ? Yellow/violet/red/gold
     
  15. kermit_xc

    kermit_xc Member

    Messages:
    84
    Location:
    Austin, TX
    nope
    IC107 1: -21.34V; 5: 5.92V
     
  16. kermit_xc

    kermit_xc Member

    Messages:
    84
    Location:
    Austin, TX
    yessir - bands match and just re-measured - we are talking about the ones right in front of the TR-149/150 - correct ?
     
    avionic likes this.
  17. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Looks like zener diode D133 may be shorted so far.
     

     

    Please register to disable this ad.

  18. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    I think so.
     
  19. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    The chip IC107 may be history as well.
     
  20. kermit_xc

    kermit_xc Member

    Messages:
    84
    Location:
    Austin, TX
    indeed it is !!! D134 looks good

    any replacement options or are we talking unobtanium ?
     

Share This Page