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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:
    216
    Location:
    Mamou, Louisiana
    .
     
    Last edited: Oct 6, 2018

     

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  2. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
  3. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    What the hell is up with AK tonight? Can the moderators please delete these empty messages?
     
  4. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    Check them with your eyes, look at them closely. Look for solder splash.
     
    Last edited: Oct 6, 2018
  5. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    Well did you find anything wrong on the Amp board?
     
  6. CavScout

    CavScout Well-Known Member

    Messages:
    566
    Not yet, out of town until tonight.
    I might be best to build a spreadsheet of all the parts on the board and record all readings.
    Being a novice the hardest thing for me is taking the readings from the front or back of the board.
     

     

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  7. CavScout

    CavScout Well-Known Member

    Messages:
    566
    I have taken a reading of all of the resistors on the right channel of the amp board and many of them are way out of spec. (Yes I will doing the left also)

    30 resistors on the right side and 7 are way below what they should be and that is after checking them several times to be certain.

    I started to check the capacitors and found a few out of spec.
    Having a stock of extra caps that fit the requirements I removed the bad ones for replacement.
    Before replacing I went ahead and checked the removed caps out of circuit and now they read just fine !!!

    Is this a common occurrence?
     
  8. Watthour

    Watthour Electron Rancher - JS3600

    Yes. The parallel circuit paths will affect any reading of components taken in-circuit. In-circuit measurements are effective to locate shorted devices, and sometimes opens, but for accurate analysis the component should be isolated. That can be as easy as removing one leg only, but transistors, SCRs, and similar devices really need to be removed.
     
    merlynski likes this.
  9. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    What Watt hour said is fact! And we already knew the right channel is ok because it is working just fine. I can tell you that something is real squirrelly going on. As I said in an earlier reply, your readings have changed in the left channel. Q9 and Q11 were reading leakage at one point in time. Now they are reading normal. Q 5 was normal at one time and now reading leakage. You should really think seriously about letting someone with experience look at your amp!
     
  10. CavScout

    CavScout Well-Known Member

    Messages:
    566
    My work schedule has finally allowed me some time to dig into this again.
    The attached image is the reading from the resistors on the right channel.
    All in circuit and read several times.
    Can there really be that many bad resistors (assuming the readings indicate "bad")
     

    Attached Files:

  11. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,888
    Location:
    uk.. the middle bit
    sorry but i do not understand your spread sheet
     

     

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  12. CavScout

    CavScout Well-Known Member

    Messages:
    566
    Example:

    Resistor R1 on the board
    In the manual it says the resistor is rated at 180k ohms
    The reading I got on it was 180k ohms

    and so on
     
  13. CavScout

    CavScout Well-Known Member

    Messages:
    566
    Just to rewind a bit...the last time I powered up the amp, neither channel was working. Right or left. It was a no sound situation (amp would not come out of protection)
     
  14. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    You will not get an accurate resistance reading with the resistors in circuit. To get an accurate reading you have to un-solder one end of the resistor and and lift it out of the circuit.
     
  15. CavScout

    CavScout Well-Known Member

    Messages:
    566
    Ok I will pull a leg on the ones that had bad readings and repost
     
  16. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    If you want to save time and effort, why don't you just compare the resistors readings on each channel without unsoldering them and see if they match readings. I highly doubt you have a resistor problem.
     

     

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  17. CavScout

    CavScout Well-Known Member

    Messages:
    566
    Ok will do, thanks
     
  18. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    216
    Location:
    Mamou, Louisiana
    Example: If right channel R13 100K reads 52.7K and left channel R14 100K also reads 52.7K, then you know those resistors are good.
     
  19. CavScout

    CavScout Well-Known Member

    Messages:
    566
    So I went through all the resistors on the other side and they match.
    I have moved on to rechecking the transistors out of circuit.
    The image shown are accurate readings from my multimeter in diode mode
     

    Attached Files:

  20. CavScout

    CavScout Well-Known Member

    Messages:
    566
    Is there a reference that I can look to for the transistors values ?
    I take the readings but I dont know what is "normal".
    I dont see them in the service manual
     

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