Pioneer SX-838 voltage problems???

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

  1. Tomcow

    Tomcow Active Member

    Messages:
    116
    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 Active Member

    Messages:
    116
    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 Active Member

    Messages:
    116
    Yes it is and those readings on the various pins were taken this morning,Regards, Tom
     

     

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  7. Tomcow

    Tomcow Active Member

    Messages:
    116
  8. Tomcow

    Tomcow Active Member

    Messages:
    116
    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 Active Member

    Messages:
    116
    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 Active Member

    Messages:
    116
    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 Active Member

    Messages:
    116
    With my ohm meter,I get 8,000 ohm each way with the black probe on the middle pin.
     
  15. Tomcow

    Tomcow Active Member

    Messages:
    116
    Til it went to K ohms,the meter was jumping all the place,then to OL
     
  16. avionic

    avionic " Black Knights " F-15 Eagle Keeper Subscriber

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    Location:
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    Looks bad to me.
     

     

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  17. Tomcow

    Tomcow Active Member

    Messages:
    116
    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 " F-15 Eagle Keeper Subscriber

    Messages:
    46,508
    Location:
    Fort Dodge, Iowa
  19. Tomcow

    Tomcow Active Member

    Messages:
    116
    All the diodes I see now just have 2 ends with the band on one end
     
  20. avionic

    avionic " Black Knights " F-15 Eagle Keeper Subscriber

    Messages:
    46,508
    Location:
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    Yes you would need two of them
     

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