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Pioneer Sa-6500II need help!

Discussion in 'Pioneer Audio' started by The Fuxtor, Dec 6, 2018.

  1. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    howdy all, I got an issue with this guy and im hoping for some advice.
    First off the unit powers up ( fails dbt). Checking thru power supply and I get very little voltage at my large filter caps.. Rectifier diodes all check out and filter caps measure a tad low in capacitance , but dont seem too bad ( although my meter doesnt measure esr). Resistors measure in spec too. I checked the switched and unswitched outlets for voltage and i read 117acv for the unswitched pair but only 19acv for the switched ones??
    My switch seems to be working ok but wouldn't this measurement point to either a bad switch or bad transformer??
    EDIT: I just jumped the switch and im getting the same readings ???
     
    Last edited: Dec 6, 2018

     

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  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,639
    Location:
    Fort Dodge, Iowa
    Did you check your output transistors?
     
  3. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    I believe at least one is bad....should I pull the outputs and recheck my power supply voltages,??
     
  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,639
    Location:
    Fort Dodge, Iowa
    yes
     
  5. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,639
    Location:
    Fort Dodge, Iowa
    That one bad one may be loading down the power supply.
     
  6. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    I dedoldered all the outputs, but same voltages?? Any other ideas to check??
     

     

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  7. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Discovered I have continuity between a collector and a base of one output, the 2sb616a transistor is dedoldered from the PCB but still mounted to heatsink?
    The continuity is on the PCB , not transistor....
    EDIT: just cleaned up the PCB around those pads, and I don't see any Bridges?? Looks very separated but still measure continuity???
     
    Last edited: Dec 7, 2018
  8. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Screenshot_20181207-095927.png Screenshot_20181207-094537.png
     
    Last edited: Dec 7, 2018
  9. avionic

    avionic " Black Knights " Subscriber

    Messages:
    44,639
    Location:
    Fort Dodge, Iowa
    Probably measuring continuity through the driver transistor.
     
  10. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Yes ..ok I will test them
     
  11. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Yes ..ok I will test them .

    Changed out the driver ( it was bad) !
    No change tho as far as ps voltages, dimbulb bright still. Would the predrivers affect power supply??
    I don't want to start chasing my tail here. What's my most logical move now?
    I should mention my outputs are still dedoldered out of circuit?
     
    Last edited: Dec 7, 2018

     

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  12. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Looking more at the sm, it looks to me like I may have more shorted components (obviously)? Not totally sure, but the protect circuit seems like it's kicked in?
    Different circuit then what I've dealt with before?? Take a look at this snip and tell me please?? Does this add up to my symptoms here??
    Edit: not exactly sure if the protection is limiting voltage , but my DC offset is showing 2dcv on both channels? How this circuit works is beyond my knowledge... Anyone care to share thoughts?
     

    Attached Files:

    Last edited: Dec 8, 2018
  13. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Anyone more familiar with this amp?? Not your typical relay speaker protection, I need to determine whats bogging the power supply down.... I'm stuck on this one?? If i pull the fuses FU3 & FU4 I get proper voltages from the transformer secondaries but once i pop them in and go to measure i get very low voltages?? Even the tap for lighting the power lamp is too low to light the lamp...
     
    Last edited: Dec 8, 2018
  14. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    anybody ??? I'm soldering in the dark here....
     
  15. Watthour

    Watthour Electron Rancher - JS3600

    Without disturbing the mounting or leads of the STVs, measure forward/revers drops on those diode stacks.
     
  16. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Thank you for the reply!
    One channel good , using meters diode function, but the other channel is OL
    in both directions! Aren't these diodes unobtanium?
     

     

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  17. Watthour

    Watthour Electron Rancher - JS3600

    Luckily, maybe not.

    There is a gentleman in Germany who seems to have acquired a stockpile of these (somehow) and is selling them on "that auction site" for a reasonable fee. I just recently purchased a quantity just to have on-hand, because they are extremely rare. The price was not horrible, and shipping was less than a week (probably Luftpost/USPS).

    If you had STV-4s, the situation might be a little different, and you would be making up a stack of diodes to replace it.
     
  18. Watthour

    Watthour Electron Rancher - JS3600

  19. Watthour

    Watthour Electron Rancher - JS3600

    Before just replacing the failed STV and other components, check for further damage.

    Also, don't trash the old STV, in case someone (MTF) wants them to repair.
     
  20. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,817
    Location:
    Calgary, Alberta
    Will do. Thank you for the assistance, much appreciated!!
     

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