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Pioneer SX-950 wont come out of protection

Discussion in 'Pioneer Audio' started by CavScout, Jul 2, 2018.

  1. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    219
    Location:
    Mamou, Louisiana
    You should be able to find it in Calgary. Wherever you go to buy one, someone there will be able to cross reference it. Look for a Industrial Electronics parts warehouse.
     

     

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  2. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    219
    Location:
    Mamou, Louisiana
    Last edited: Jul 8, 2018
  3. CavScout

    CavScout Well-Known Member

    Messages:
    578
  4. CavScout

    CavScout Well-Known Member

    Messages:
    578
    Will there be a problem with the NTE ?
     
  5. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,063
    Location:
    uk.. the middle bit
    possibly but may well be ok for a regulator as it is being used for .
     
  6. CavScout

    CavScout Well-Known Member

    Messages:
    578
    Ok I will put it in there and see what happens
     

     

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  7. CavScout

    CavScout Well-Known Member

    Messages:
    578
    Put in the NTE Transistor

    Good news.......OUT OF PROTECTION AND PLAYING MUSIC ! YES !

    Bad news.......lots of distortion. Sounds like a crappy $5 stereo, even at low volume.

    Can this be the transistor?
     
  8. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,063
    Location:
    uk.. the middle bit
    check the voltages again .
     
  9. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,063
    Location:
    uk.. the middle bit
    if voltages ok we need to check the idle biases . and dc offsets
     
  10. CavScout

    CavScout Well-Known Member

    Messages:
    578
    Readings on Q5

    Base 41.7v DC
    Emitter -37.4v DC
    Collector 36.9v DC
     
  11. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,063
    Location:
    uk.. the middle bit
    you got those mixed up and marked one negative .
    should be
    collector 41.7v DC
    base -37.4v DC
    emitter 36.9v DC
    looking good when it is correct way round ..
     

     

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  12. CavScout

    CavScout Well-Known Member

    Messages:
    578
    Yes, sorry, no neg voltages.

    So how do I check idle bias and DC offset ?
     
  13. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,063
    Location:
    uk.. the middle bit
    now go to page 38 and study but ignore the 5.1k resistors as not needed . and do not touch the trimmers apart from vr1 and vr2 . set to 0v if possible .then just monitor the voltages for 10 minutes parts 8 9 and 10 .
     
  14. CavScout

    CavScout Well-Known Member

    Messages:
    578
    What do they mean by " set the power amplifier for NO LOAD" ?

    28, 27,13 and 12
    Have references to + and -
    Does this mean the multimeter is hooked to both of those at once or are all these readings with the ground to frame?
     
  15. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,063
    Location:
    uk.. the middle bit
    both and your meter can go either way if dmm type .. that was written for analogue meters as dmm.s not available back then .
     
  16. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,063
    Location:
    uk.. the middle bit
    no load is no speakers .
     

     

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  17. CavScout

    CavScout Well-Known Member

    Messages:
    578
    I made the adjustments and it sounded good for a few seconds but lots of distortion still
     
    Last edited: Jul 9, 2018
  18. CavScout

    CavScout Well-Known Member

    Messages:
    578
    Went back to make all of the adjustments. Everything was going well when vr4 was between 15 and 20mv I heard the protection relay click on and off a few times and now it won't come out of protection.
    Also the Vr readings are:

    Pins 9&10
    -38.9v ( I had it very close to zero)
    Pins 12&13
    .113v ( I had it at 20mv)
    Pins 24&25
    .092v (I had it very close to zero)
    Pins 27&28
    .211v ( I had it at 20mv)
     
  19. CavScout

    CavScout Well-Known Member

    Messages:
    578
    Also getting a faint glow through the DBT
     
  20. Watthour

    Watthour Electron Rancher - JS3600

    It is reasonable to surmise that the power supply regulator transistor failed due to a fault and not from age. Excessive load is often the case. This can be from a faulty component downstream of the power supply, and that faulty component(s) can be creating the distortion you are hearing.

    The faint glow of the DBT can be normal. If the power supply voltages are now within a normal range, the real troubleshooting can begin.
     

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