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Output transistors keep blowing on SX-2500

Discussion in 'Pioneer Audio' started by PoDuck, Nov 16, 2018.

  1. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    541
    Location:
    High Plains, Eastern Colorado
    That would seem to be the next step, look for leaky caps. Have a good evening!
     

     

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  2. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,084
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    uk.. the middle bit
    R17 in spec ?
     
  3. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,084
    Location:
    uk.. the middle bit
    yep a ceramic cap might be bad here . or C7
     
  4. KeithD

    KeithD AK Subscriber Subscriber

    Messages:
    648
    Location:
    La Crosse, WI
    Make sure your main amp board matches the SM you are using. I picked up a service manual, and the main amp board layout in this SM is not the same as the one posted on HiFiEngine. I've scanned the one from my service manual (in color) and uploaded the one from the HiFiEngine manual for comparison.

    Pioneer 2500 Main Amp.jpg
     

    Attached Files:

    Noodle likes this.
  5. PoDuck

    PoDuck AK Subscriber Subscriber

    Messages:
    117
    Other than slight differences, the one I have matches very closely. That one resistor being on the wrong side, and the other two resistors showing the wrong value are the only two discrepancies I've found so far, and they are the same on your images too. Both.
     
  6. KeithD

    KeithD AK Subscriber Subscriber

    Messages:
    648
    Location:
    La Crosse, WI
    OK, I have not been following all of the details of what you are doing. I just noticed recently while working on my 2500, the two board diagrams are not the same.
     

     

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  7. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    541
    Location:
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    Thanks for the upload!
    KeithD, Do you have a signal generator and an oscilloscope? We could really use some pictures of signals from a working unit, specifically in Seperate, with a sine wave 1kHz 200mV p-to-p Main input and pins 9 and 4 (output returns) from the main amp unit,
    Thanks in advance!
     
  8. KeithD

    KeithD AK Subscriber Subscriber

    Messages:
    648
    Location:
    La Crosse, WI
    Yes, have scope and can get my hands on a signal generator. However, I am currently working on my 2500. Right channel has a lot of distortion. Pretty sure one of the transistors is blown. If I have time, I plan to work on this Saturday or Sunday. Possible I could get to it earlier, but with family obligations I don't have a lot of spare time to work on these things. Will get back to you when I can.

    This is an interesting thread for me, so thanks for all the posts.
     
    merlynski likes this.
  9. LesE

    LesE 110284 Subscriber

    Messages:
    876
    Location:
    Ontario, Canada
    Until you get the the real thing, here is what the simulation shows for Pin 4.

    upload_2018-12-7_14-32-24.png

    Edit: Pin 4 waveform for corrected simulation. 200mV p-p input, 9.4V p-p output. 8 ohm load
     
    Last edited: Dec 7, 2018 at 1:42 PM
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  10. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    541
    Location:
    High Plains, Eastern Colorado
    Thanks, LesE, are you using Ltspice? If so which release? Will you share the sim file, please?
    What is the sims input level? Was that to Main input? I see the pin 4 signal is 200mv p-p.
     
    Last edited: Dec 6, 2018 at 4:38 PM
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  11. LesE

    LesE 110284 Subscriber

    Messages:
    876
    Location:
    Ontario, Canada
    Yes, LTspice XVII. The input level is 200mV p-p and the Pin 4 signal is 20mV 9.4V p-p.

    Note that I threw this together quickly and I didn't bother to set the component designations to match the schematic (too lazy :) )

    SX-2500 LTspice Files

    Please let me know if you find any errors.

    Les.
     
    Last edited: Dec 7, 2018 at 1:50 PM
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  12. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    541
    Location:
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    Thanks much! :thumbsup: I use XVII as well, though I am very new at it :biggrin:
     
  13. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    28,084
    Location:
    uk.. the middle bit
    i can only guess R17 is in spec . just thinking about the extra 400mv difference from good channel .
    plus the vr.s not behaving properly .. C11 . 100uf 50v .
    maybe throw a leaky cap into spice ... :D:idea:
    q3 is my next guess
     
    Last edited: Dec 6, 2018 at 7:10 PM
  14. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    541
    Location:
    High Plains, Eastern Colorado
    LesE, I seem to be missing the MJ21196.lib file
    EDIT: Got it Thanks
    Well dang, now it wants KSC2383.lib, How about just post all the lib files it calls?
    Thanks again
     
    Last edited: Dec 6, 2018 at 5:46 PM
  15. LesE

    LesE 110284 Subscriber

    Messages:
    876
    Location:
    Ontario, Canada
    Should be on the Onsemi site or I can add it to the folder if that is easier.

    Edit: Added the .lib to the folder
     
  16. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    541
    Location:
    High Plains, Eastern Colorado
    Well dang, now it wants KSC2383.lib, How about just post all the lib files it calls?
    Thanks again
     

     

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  17. LesE

    LesE 110284 Subscriber

    Messages:
    876
    Location:
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    I think they're all there now.
     
  18. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    541
    Location:
    High Plains, Eastern Colorado
    Thank you! I did figure out how to get it from Onsemi - learn something every day on AK! :rockon:
    And it now runs the sim. :bowdown:
     
  19. LesE

    LesE 110284 Subscriber

    Messages:
    876
    Location:
    Ontario, Canada
    Glad I could help. LTspice is a tremendous tool and I wouldn't do a restoration anymore without building a simulation first.
     
  20. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    541
    Location:
    High Plains, Eastern Colorado
    I still have a LOT to learn!
    I did notice that node Pin 4 was not connected (graphically) to the Output side of the output capacitor, which is half of the negative feedback path, through the two 15kΩ resistors. Was that deliberate or an oops?
     

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