SX-880 in Protection

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

  1. petehall347

    petehall347 the brandy coffee man Subscriber

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    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

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    am wondering if pa3004 was damaged when q36 shorted
     
  3. Motnick

    Motnick AK Subscriber Subscriber

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    Relay does not engage with Q36 removed.
     
  4. Motnick

    Motnick AK Subscriber Subscriber

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    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

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    all i can suggest is try changing c418 c419 and checking resistor values
     
  6. Motnick

    Motnick AK Subscriber Subscriber

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    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

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    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 AK Subscriber Subscriber

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    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

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    yep lift a leg to be sure
     
  11. Motnick

    Motnick AK Subscriber Subscriber

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    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 AK Subscriber Subscriber

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    I pulled C417 completely out from the board. PA3004 voltages are the same.
     
  14. petehall347

    petehall347 the brandy coffee man Subscriber

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    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 .
     
  15. Motnick

    Motnick AK Subscriber Subscriber

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    Finally getting back around to this project. I’ve been looking for a PA3004 replacement, but so far no luck.

    I went ahead and pulled Q35: PA3004 today and found this installed. Is this part equivalent to PA3004? I was expecting it to say PA3004 not HA1457. I think HA1457 is an opamp, isn’t it?

    [​IMG]
     
    Last edited: Dec 22, 2018
  16. rcs16

    rcs16 Super Member

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    Different animal, in the same skin.
    HA1457 is a high voltage low noise pre-amp.
    I bought a few PA3004 on ebay to try out, I will let you know if that source is legit or not when they arrive.
    Make reference to where that HA1457 part is used, assembly #,reference designator, you might have pulled the wrong part.
    I have used the Hitachi HA12002, it is Hitachi's version of a speaker protector IC
     

     

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  17. petehall347

    petehall347 the brandy coffee man Subscriber

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    HA1457 is phono amp ic .. should be 2 in there q1 q2
     
  18. Motnick

    Motnick AK Subscriber Subscriber

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    Yes I did find the other two that are supposed to be in the unit, but why is HA1457 also installed at Q35? Someone must have installed this by mistake during an earlier repair attempt? Am I correct in thinking that HA1457 is not going to work at Q35, and that this is what’s causing my protection issues?
     
    Last edited: Dec 22, 2018
  19. petehall347

    petehall347 the brandy coffee man Subscriber

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    yes looks like you found the issue ..i wonder how it managed to work at all . :idea:
     
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  20. Motnick

    Motnick AK Subscriber Subscriber

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    It never did for me. I can only assume it was a failed repair attempt by someone before me.

    Geez, first wrong sized emitter resistors in one of the power amp boards of my SX-980, and now this! I guess I should have verified what was installed at Q35 as a first step.

    Should I try one of the eBay PA3004 ICs?
     
    Last edited: Dec 22, 2018

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