Pioneer Sx1010 Repair - Diodes

Discussion in 'Pioneer Audio' started by 70smidfiguy, Dec 16, 2018.

  1. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    One last test for fun. I put all of the old transistors back in one of the two boards.

    Same result as above.
     

     

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  2. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    I'm sorry you are having such issues with this receiver.
    The amp boards get/need two sources of voltage to operate.
    The pre-stage section gets the regulated +-54 volts from the power supply. And:
    The outputs and some drivers (the heatsink transistors on the boards) get their power from the unregulated voltage via the rectifier and big caps.

    So let's do some recap on the voltages just to make sure we'er back on the same page.
    On the DBT, with the resistors in place of the outputs, volume to min, no input sources and no jumpers installed.
    Report the PS voltages once again. Black probe to chassis ground, bare clean metal chassis connection.
    By now you should know what pins are AC and what read DC(?).

    If the DBT is bright find the short before moving on. Don't run it with the bulb bright.

    Report the current Protection voltages as well.
     
  3. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Exactly my thoughts, thanks!

    So ive taken out the amp boards, will measure all key voltages on core boards and post (might help someone down the road)

    Cheers
     
  4. 70smidfiguy

    70smidfiguy Active Member

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    Location:
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    Readings from yesterday, no Amp boards installed - Direct AC:

    GBC-FASHADSKTP 2019-01-26 1.05.59 PM .jpg GBC-FASHADSKTP 2019-01-26 1.06.34 PM .jpg
     
  5. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    I'm looking at the readings.
    Noticed the +-24 volt readings are 5 volts difference. Out of the PS your reading +27v and the other -23v.
    The phono EQ or the Control amp is open and not using the +24v feed/supply. That 5v difference is too much.
    This is something that should be fixed before moving on.
    It might be a broken +24 volt supply wire to one of the positive supply pins on the EQ or control amp boards.

    I'm still checking your readings.
    Image both sides of one of the amp boards (Right one first) so I can check placements and look at the traces.
    Leave them as thumbnails, that way they will be magnified as large as they can.
     
  6. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    I also removed the Control Amplifier Assembly (AWG-027) cleaned all connections.
    Everything looks pretty good, however when I test pin 15 on the PS I still get about 26.x v vs PIN 11 PS which is -23.x v.

    The only tr's on that board are 2 x KSA992 (replaced) and 6 x 2SC1312's.

    Could the pots be an issue?

    Thanks.
     

     

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  7. goat67

    goat67 AK Subscriber Subscriber

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    The pots can and do go bad not saying this is the cause of your problems though
     
  8. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    R13 on the PS board AWR-054. What is the resistance reading?
    I would like the images of the amp boards front and back.
    Right first or both.
     
  9. 70smidfiguy

    70smidfiguy Active Member

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    Location:
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    R13 which is a 1.2K resistor measures at 1.158K.

    Pictures of Rch Amp Board enclosed
     

    Attached Files:

  10. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
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    Your image of the output installation is incorrect. Please edit or delete the post.

    The image below is correct and from a 1010 that is original in condition.

    DSC05205.JPG

    NPN - NPN - PNP - PNP

    The image is top is top and bottom is bottom.
     
  11. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    These are installed correctly.
    Check yours.
    I'll keep working this amp and will post images as I go.

    DSC05210.JPG

    DSC05209.JPG
     

     

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  12. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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  13. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    20190131_222233.jpg 20190131_222332.jpg
    @zebulon1 ^^The screws holding Q9 and Q10 (TO-220) to the board rch heatsink do not appear to have insulators under the screw heads, and the insulators between the tabs and the heatsink are rippled and not laying smooth. Maybe shorted? +55vdc to -55vdc?
     
    Last edited: Feb 1, 2019
  14. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    They don't need the screw insulators. The heatsink has a plastic nut-plate secured to the heatsink.
    I did see the poor sil-pad install.
     
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  15. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Thanks, I could see something back there in another view but did not know what it was, didn't see anything in the manual. :thumbsup:
     
  16. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
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    Thank you so much! I will repost the output tr's when corrected to be sure.

    Thanks again for being so patient with me on this.

    Cheers

    Cam
     

     

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  17. 70smidfiguy

    70smidfiguy Active Member

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    Correct Output TR orientation for SX-1010:

    20190201_202956.jpg
     
  18. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
  19. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    So after getting orientation correct above, reconnected all on DBT, light dims completely. No protection circuit though.

    Will now go back and check DC Offset/Bias all other voltages.

    Preamp jumpers are out.
     
  20. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Update:

    On DBT:

    Lch

    Pin 10 - 481mv
    Pin 13 -368mv

    These are adjustable with VR1 and VR2

    Rch

    Pin 10 -14v
    Pin 13 -9.7v

    These are also adjustable with VR1 and VR2

    Some progress :)

    Next step?
     

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