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Pioneer SX-1250 Restore - Some Heat Q's

Discussion in 'Pioneer Audio' started by ivandezande, Oct 5, 2018.

  1. ivandezande

    ivandezande Super Member

    Messages:
    1,638
    Location:
    Twin Cities
    Just went through an abused but working 1250 (a crappy DJ owned it for several years way back) and I replaced all caps many transistors and a few zeners, but now I wondering about heat. The heatsink on the stabilizer board gets very toasty quickly, and the resistors above the main diode bridges do as well. Is this something I should be worried about and try to remedy?
     

     

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  2. kevzep

    kevzep Its all about the Music

    I would rebuild the entire stabiliser board.
    There is a list somewhere here for that.
    The nature and design of the stabiliser board means there is a lot of heat produced as a result of the regulation.
     
  3. rcs16

    rcs16 Super Member

    Messages:
    3,888
    Location:
    Baldwin, Ontario, Canada
    You replaced the bjts and ecaps already in the PS, the heat is not going to go away, all you can do is to minimize component op temps, like adding more/bigger heatsinks to the series pass bjts regs to lower their Tj which improves reliability.
    You could go nuts and replace everything as Kev suggests for a piece of mind & improved long term reliability, predicting when a film or ceramic cap will fail is in the lottery dept.
     
  4. Watthour

    Watthour Electron Rancher - JS3600

    One of the hotter devices on the stabilizer board, and a potential way to help cool it:

    [​IMG]
     
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  5. kevzep

    kevzep Its all about the Music

    I put extra heat sink-ing there too.
    Not quite as extreme though, but it definitely helps...
    IMG_6598.JPG
     
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  6. petervv

    petervv Active Member

    Messages:
    104
    Location:
    Netherlands
    And my implementation :) :

    IMG_0065.JPG
     
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  7. Rico126

    Rico126 Active Member

    Messages:
    245
    Location:
    Pittsburgh, PA
    All 3 are pretty good ideas
     
  8. kevzep

    kevzep Its all about the Music

    Which is what caught me out on that 1250 I was working on......
    So really, everything is becoming suspect these days, I used to rule out ceramic caps, but I have found a few shorted and intermittent ceramics lately...so this is now part of my failure mode when looking at problems in circuits..
     
  9. rcs16

    rcs16 Super Member

    Messages:
    3,888
    Location:
    Baldwin, Ontario, Canada
    everything is suspect but as for failing, only time will tell. :)
    Basically fix them as they fail.
    Even new components fail, the bath tub curve on comp reliability.
    I once worked at a HP lab, had a EE who's sole job was component reliability analysis and regulatory certification. We hand him our design BOM's, he'd have to okay every comp, assess risks, come up with reliability numbers. Top of the list was moving parts, ecaps :) were forced to use kemet fused tantalums, just in case of a assembly reversal and possible fire.
    finding caps failing anywhere can be a challenge esp if they fail open or way out of spec. RF sections are a PITA to fix
     
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  10. WE6C

    WE6C Well-Known Member

    Messages:
    516
    Location:
    Colfax, Northern California
    When I did mine I also added a small heat sink to it however I bought it new back in 1976 and never had a problem with it. I went thru it in 2016 so no problems in 40 years with regular use! The heat must not have hurt anything but it gave me a little piece of mind with an additional heat sink. FWIW.

    An infa-red heat gun is a good tool to own.

    Bob
     
  11. rcs16

    rcs16 Super Member

    Messages:
    3,888
    Location:
    Baldwin, Ontario, Canada
    IR heat guns are great tools to own, cheaper thermocouples but not as accurate
    rule of thumb every 10C rise in Tj reduce the life by 1/2
     

     

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