no change in one channel when adjusting idle current on pioneeer sx-1050

Discussion in 'Pioneer Audio' started by kubotadave, Feb 9, 2019.

  1. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
    5,056
    Location:
    Las Vegas Nevada
    Do you have a DBT?
    Watthour is saying the output transistors are not conducting and no current is flowing through them.
    With the receiver on the DBT. Volume turned to min/down and no inputs. Clip the black DMM lead to chassis and the red probe to pin 24. Adjust the idle trimmer from full CCW to CW and watch the DMM for DC voltage. Return the trimmer back to min, full CCW.
    The range is from millivolts to a few volts.
    Then clip to pin 28 and perform the above procedure once again.
    Record and report.

    You can perform this procedure to the good channel and see for yourself the differences. Easy on the trimmer when going full to full idle. It will open up the outputs. Just do enough trimmer too see the good side working correctly.

    The procedure is checking the driver circuit.
     

     

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  2. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    Unfortunately i dont have one.Any thoughts on where i could purchase one?
     
  3. ivandezande

    ivandezande Super Member

    Messages:
    1,958
    Location:
    Twin Cities
    Home Depot/Lowes. The plans are everywhere on AK, just do a site search for it and it should pop up.
     
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  4. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
    5,056
    Location:
    Las Vegas Nevada
    Build one.
    http://audiokarma.org/forums/index.php?threads/dim-bulb-tester-build-and-how-to.808399/

    The jest is, the bulb is in series with the units power. If the receiver has a short the bulb covers the load and glows bright (This is Bad). If the receiver has no short or potential to ground the bulb is dim (This is Good).
    Others can explain it much better but you need to build one. The circuit diagram in the thread is the key. You can use salvaged components to build your DBT.
    You'll need at least a 100 watt bulb for the DBT when using it on your 1050.

    By the way. Can you update your profile and list the city you reside?
     
    Last edited: Feb 11, 2019
  5. Watthour

    Watthour Electron Rancher - JS3600

    If you have a noted copy of the schematic, you can compare your measured voltages with those marked around Q14, 16, 18, and 20.

    I am also a bit confused over the reported voltages. Post # 7 indicated that Power Amp board pins 3 & 18 had the correct -60V supply for the L and R channels, and that the corresponding PNP emitter sense voltages on pins 2 (L channel) and 19 ((R channel) were WAY off:

    1= 59.7
    2= 40mv
    3= -59.4
    4= 34mv
    5= 0
    6= 0
    7= -58.7
    8= 0
    9= 0
    10= 63
    11= 0
    12= 0
    13= -58.7
    14= -58.7
    15= 0
    16= 0
    17= 0
    18= -60
    19= 60.8
    20= 0

    The reported voltage readings from the Protection board in Post # 17 don't quite seem to correspond, showing that pins 7 (L channel) and 5 (R channel) had notable differences:

    1) 0
    2) -12.6
    3) 7.43ac
    4) 27mv
    5) -37mv
    6) 30mv
    7) 37mv
    8) -30mv
    9) 0mv
    10) 0
    11) 33mv
    12) 62.5v

    Before proceeding elsewhere, it might be good to test the emitter resistors for the outputs (½Ω / 5W) for continuity.
     
  6. Watthour

    Watthour Electron Rancher - JS3600

     

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  7. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    built a dim bulb tester with a 150 watt bulb.Sorry DBT thgrough me off.lol
     
  8. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
    5,056
    Location:
    Las Vegas Nevada
    The 150 watt is fine.
    Good, your on your way.
    You-Tube has lots of info on the operation of the DBT.
    It's a current limiter. The receiver won't work properly when plugged in to the DBT but you can get voltages needed for troubleshooting.
    I use it when powering up on line voltage after making any changes or repairs to any circuit on the receiver. You never know what was jimmied when your mucking about inside. The vintage sets are fragile and anything can give way without notice, let alone your own mistakes.
     
  9. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    OK test results in
    pin 24) -12.3
    pin 28)14.4
    No change when turning vr4
    pin 33)50mv
    pin29) -50mv
    dialed in nicely with vr3
     
  10. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    The bulb didnt change when i plugged the reciever in to do testing.Stayed bright
     
  11. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    all of the emitter resistors .5 ohms
     

     

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  12. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
    5,056
    Location:
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    Did you test the DBT before you used it on the 1050?
    A bright bulb means there's a short in the receiver.
    An incandescent bulb is what you should use in the DBT.
     
  13. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    My mistake i had the bulb wired parralell instead of series.bulb came on bright and then dim almost out,but did not blow
     
  14. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
    5,056
    Location:
    Las Vegas Nevada
    That’s better.
     
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  15. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    amp board double checked
    1)53.8
    2)46mv
    3)-53.7
    4)43mv
    5)0
    6)41mv
    7)-58.3
    8)0
    9)0
    10)62.3
    11)0
    12)0
    13)-58.4
    14)-58.2
    15)0
    16)0
    17)0
    18)-54
    19)0
    20)53.6
     
  16. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    protection board readings
    1)0
    2) -12.6
    3)7.43ac
    4)53mv
    5)-31mv
    6)44mv
    7)49mv
    8) -8mv
    9)0
    10)0
    11)46
    12)62.5
     

     

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  17. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    power supply awr-103
    1)20.8
    2)-014mv
    3)-70.4
    4)0
    5)13.3
    6)13.3
    7)-12.5
    8)-58.3
    9)-29.4
    10)-23.9
    11)-23.9
    12)0
    13)25.7
    14)25.7
    15)31.6
    16)62.6
    17)62.6
    18)5.98
    19)5.97
     
  18. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    still powers on no sound.soft relay clicks.speaker protect relay no movement
     
  19. Watthour

    Watthour Electron Rancher - JS3600

    Thanks for posting the updated voltages. There is still a difference at Pins 4 & of the protection board which exceeds the bias voltage of the transistor (Q2) and is likely due the the inability to adjust the bias of the amp circuit.

    I still think it would be good to test the voltages at Q14, 16, 18, and 20.
     
  20. kubotadave

    kubotadave New Member

    Messages:
    43
    Location:
    watertown ny
    I definitely will and post my results tomorrow.Alittle burned out tonight.
     

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