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Pioneer SX-950 wont come out of protection

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

  1. CavScout

    CavScout Well-Known Member

    Messages:
    566
    The reading is 1.76
     

     

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  2. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
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    Check D3. The small glass diode connected to pin 7. I feel as though it is shorted. Give me the reading across that diode!
     
  3. CavScout

    CavScout Well-Known Member

    Messages:
    566
  4. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    OK, now check the other 3 diodes the same way. D1, D7 and D9
     
  5. CavScout

    CavScout Well-Known Member

    Messages:
    566
    D1 .572
    D5 .533
    D7 .528
     
  6. petehall347

    petehall347 the brandy coffee man Subscriber

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    Location:
    uk.. the middle bit
    if that is d5 amp board ding ding
     

     

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  7. 1MEGΩ

    1MEGΩ Active Member

    Messages:
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    Location:
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    Well D5 is the STV-4H biasing diode. If it is reading .533, then it is bad. Are you sure about that? What about D9??

    Please take a picture of this D5 you just mentioned!!
    Is the D5 you just checked the one with the long white insulated leads??
     
    Last edited: Oct 6, 2018
  8. CavScout

    CavScout Well-Known Member

    Messages:
    566
    Oops, I stand corrected ( I thought that 9 was a 5 on the schematic)

    Correct info is

    D1 .572
    D9 .533
    D7 .528

    D5 is 1.215
     
  9. petehall347

    petehall347 the brandy coffee man Subscriber

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    Location:
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    d5 seems low compare to d6
    may have used schottky string in those if d6 same
     
  10. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    All the diodes in the left channel are good!
     
  11. petehall347

    petehall347 the brandy coffee man Subscriber

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    Location:
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    d6 is the other channel and good comparison .
     

     

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  12. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
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    I agree, he should compare the 2 STV-4H diodes. Other than that, maybe two traces on the back side of the board are touching through a solder joint.
     
  13. petehall347

    petehall347 the brandy coffee man Subscriber

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    Location:
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    just measure the known good one first .
     
  14. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    But the fact is that even if the STV-4H was completely shorted, it would not cause the leakage across the emitter and collector of Q5. So the STV-4H is not the problem.
     
  15. petehall347

    petehall347 the brandy coffee man Subscriber

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    yes it was academic . but things like this might be the cause of the problem . no harm in checking .
     
  16. 1MEGΩ

    1MEGΩ Active Member

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    Location:
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    I did check and putting a short across the STV-4H does not cause a reading between the emitter and collector of Q5. That junction should read open.
     

     

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  17. CavScout

    CavScout Well-Known Member

    Messages:
    566
    D6 is 1.211
     
  18. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,888
    Location:
    uk.. the middle bit
    d5 is not a concern then .
     
  19. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    Check the foil side (back) of the Amp board for shorts between the foils. And check every resistor in the circuit. You can make comparisons on the right channel. Also check all the caps too.
     
  20. CavScout

    CavScout Well-Known Member

    Messages:
    566
    How do I check for shorts between the foils with a multimeter?
     

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