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Pioneer SX-838 voltage problems???

Discussion in 'Pioneer Audio' started by Tomcow, Oct 6, 2018.

  1. Tomcow

    Tomcow Member

    Messages:
    61
    Pioneer SX-838 powers on but no relay.Getting strange voltmeter readings on both power supply board and protection board.PS,pin 1,-21mv,pin 2,plus 20mv,pin 3,plus 20mv,pins 4 and 5,plus and - 41V,pin 6,0mv,pin 7,-43V,pins 8 and 9,-155mv,pins 10 and 11,plus 10V,pins 12 and 13,plus 14V,pin 14,plus 12.7V,pins 15 and 16,0mv,pin 17,plus 49V,pins 18 and 19,minus 187mv,pin 20,0mv,pin 21,7V,pin 22,6mv,pin 23,plus6.2mv,pin 24,-6.3mv
     

     

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  2. Tomcow

    Tomcow Member

    Messages:
    61
    Protection Board:pin 1,plus 10V,pin 2,-156mv,pin 3,-12.8V,pin 4,0mv,pin 5 and 6,plus 10V,pins 7 and 8,-12.9V,pin 9,plus 3.8V,pins 10 and 11,plus 14.7V,pin 12,plus 7.4V,(AC)
     
  3. Watthour

    Watthour Electron Rancher - JS3600

    A little clearer format (then I'll try to digest them):

    Power Supply:
    Pin 1, -21mV,
    Pin 2, + 20mV,
    Pin 3, + 20mV,
    Pins 4 and 5, ±41V,
    Pin 6, 0mV,
    Pin 7, -43V,
    Pins 8 and 9, -155mV,
    Pins 10 and 11, + 10V,
    Pins 12 and 13, + 14V,
    Pin 14, + 12.7V,
    Pins 15 and 16, 0mV,
    Pin 17, + 49V,
    Pins 18 and 19, minus 187mV,
    Pin 20, 0mV,
    Pin 21, 7V,
    Pin 22, 6mV,
    Pin 23, +6.2mV,
    Pin 24, -6.3mV

    Protection Board:
    Pin 1, + 10V,
    Pin 2, -156mV,
    Pin 3, -12.8V,
    Pin 4, 0mV,
    Pin 5 and 6, + 10V,
    Pins 7 and 8, -12.9V,
    Pin 9, + 3.8V,
    Pins 10 and 11, + 14.7V,
     
    Last edited: Oct 6, 2018
  4. Watthour

    Watthour Electron Rancher - JS3600

  5. Watthour

    Watthour Electron Rancher - JS3600

    Check the voltages on the PS board Pins 1, 2, 3, 18, 19, 22, 23, & 24 on an AC volts scale.
     
  6. Tomcow

    Tomcow Member

    Messages:
    61
    Yes it is and those readings on the various pins were taken this morning,Regards, Tom
     

     

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  7. Tomcow

    Tomcow Member

    Messages:
    61
  8. Tomcow

    Tomcow Member

    Messages:
    61
    Ok.pin 1,37.5V,pin 2,31.7V,pin3,31.7V,pin 18,38.9V,pin 19,38.9V,pin 22,7.5V,pin 23,7.7V,pin24,6V all read with voltmeter on AC.
     
  9. Watthour

    Watthour Electron Rancher - JS3600

    So the updated measurements are:

    Power Supply:
    Pin 1, 37.5VAC,
    Pin 2, 31.7VAC,
    Pin 3, 31.7VAC,
    Pins 4 and 5, ±41V,
    Pin 6, 0mV,
    Pin 7, -43V,
    Pins 8 and 9, -155mV,
    Pins 10 and 11, + 10V,
    Pins 12 and 13, + 14V,
    Pin 14, + 12.7V,
    Pins 15 and 16, 0mV,
    Pin 17, + 49V,
    Pin 18, 38.9VAC,
    Pin 19, 38.9VAC,
    Pin 20, 0mV,
    Pin 21, 7V,
    Pin 22, 7.5VAC,
    Pin 23, 7.7VAC,
    Pin 24, 6VAC

    Protection Board:
    Pin 1, + 10V,
    Pin 2, -156mV,
    Pin 3, -12.8V,
    Pin 4, 0mV,
    Pin 5 and 6, + 10V,
    Pins 7 and 8, -12.9V,
    Pin 9, + 3.8V,
    Pins 10 and 11, + 14.7V,
     
  10. Tomcow

    Tomcow Member

    Messages:
    61
    Yes.All the readings are taken in dc,except the ones you told me to check in ac.Regards,Tom
     
  11. Watthour

    Watthour Electron Rancher - JS3600

    Does the dual diode bridge D6 check out good?
     

     

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  12. Tomcow

    Tomcow Member

    Messages:
    61
    Is that the little square black box with the 2 arrows on top pointing at each other?3 pins going into the board? What should it read?
     
  13. Watthour

    Watthour Electron Rancher - JS3600

    That's the square box. The two arrows each represent one diode. Those can be tested for resistance in the forward/reverse direction using the center (common) lead as a reference for each diode. The resistances should be around 500Ω in the forward direction and at least 1,500Ω in the reverse direction for each half.
     
  14. Tomcow

    Tomcow Member

    Messages:
    61
    With my ohm meter,I get 8,000 ohm each way with the black probe on the middle pin.
     
  15. Tomcow

    Tomcow Member

    Messages:
    61
    Til it went to K ohms,the meter was jumping all the place,then to OL
     
  16. avionic

    avionic " Black Knights " Subscriber

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    Looks bad to me.
     

     

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  17. Tomcow

    Tomcow Member

    Messages:
    61
    Is this the SR3am-8 rectifier?It could certainly cause all the voltage problems on the PS board,I would think.Could it be replaced with a 512-1N5404?
     
  18. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,669
    Location:
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  19. Tomcow

    Tomcow Member

    Messages:
    61
    All the diodes I see now just have 2 ends with the band on one end
     
  20. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,669
    Location:
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    Yes you would need two of them
     

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