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SX-880 in Protection

Discussion in 'Pioneer Audio' started by Motnick, Oct 22, 2018.

  1. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,886
    Location:
    uk.. the middle bit
    pull q36 and see if relay clicks .or might be easier to lift one end of R419 8.2K .
     

     

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  2. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,886
    Location:
    uk.. the middle bit
    am wondering if pa3004 was damaged when q36 shorted
     
  3. Motnick

    Motnick Active Member

    Messages:
    338
    Location:
    Wyandotte Michigan
    Relay does not engage with Q36 removed.
     
  4. Motnick

    Motnick Active Member

    Messages:
    338
    Location:
    Wyandotte Michigan
    I was also wondering something along these lines, but I wasn’t sure if I had done an adequate enough job of ruling everything else out.

    Does PA3004 have a substitute? Do I need to look for a good used one?
     
  5. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,886
    Location:
    uk.. the middle bit
    all i can suggest is try changing c418 c419 and checking resistor values
     
  6. Motnick

    Motnick Active Member

    Messages:
    338
    Location:
    Wyandotte Michigan
    I replaced C418 and C419, but it didn’t help. The same voltages remain at PA3004.
     

     

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  7. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,886
    Location:
    uk.. the middle bit
    seem to remember you changed c417 and verified its polarity .
    i would check the soldering then if still no use try a new pa3004 .
     
  8. Watthour

    Watthour Electron Rancher - JS3600

    You could just lift C417 and see if the voltage at PA3004 Pin 8 comes up at all.

    Also, that seems to be a LOT of AC on Pin 7. Are the two resistors in the divider (R403/404) intact?
     
  9. Motnick

    Motnick Active Member

    Messages:
    338
    Location:
    Wyandotte Michigan
    R403 and R404 both measure .5M ohm in circuit. 1M ohm - Brown, Black, Green, Gold.

    Maybe I need to lift one leg to get a proper reading?
     
  10. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,886
    Location:
    uk.. the middle bit
    yep lift a leg to be sure
     
  11. Motnick

    Motnick Active Member

    Messages:
    338
    Location:
    Wyandotte Michigan
    I went ahead and lifted a leg on both resistors. They both measure 1M ohm.
     

     

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  12. Watthour

    Watthour Electron Rancher - JS3600

    And did you pull C417? That will, of course, eliminate any timing delay of the protection circuit, so be sure the volume is at minimum and/or there is no signal present - Or disconnect the speakers.
     
  13. Motnick

    Motnick Active Member

    Messages:
    338
    Location:
    Wyandotte Michigan
    I pulled C417 completely out from the board. PA3004 voltages are the same.
     
  14. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,886
    Location:
    uk.. the middle bit
    there is a recent thread about the pa3004 . not the same issue though .. i see yours is appearing to be barely turning the relay driver transistor on .

    you may have read this already . http://audiokarma.org/forums/index.php?threads/pioneer-pa3004-ic-required.760886/

    only thing i can suggest right now is removing the base connection for the relay drive transistor and measuring voltages again at pa3004 .. i expect them to be the same though .
     

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