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ANYONE FAMILIAR WITH THE MCS 3125??

Discussion in 'Solid State' started by Rex Runner, Nov 10, 2018 at 9:44 AM.

  1. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    Replaced the filter caps
    Large watt resistors in area of rectifiers got hot
    replaced 2 of them
    Still in protect
     

     

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  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
    Fort Dodge, Iowa
    Does this model have transistor outputs or STK outputs?
     
  3. MCS Guy

    MCS Guy The MCS hoarder Subscriber

    Messages:
    540
    Location:
    FL
    Ok, I'll try to help you out, but if this is over your head, I recommend taking the unit to a repair shop.

    First, Check voltage at your filter caps. Make sure BOTH sides have their +/- 63 volts. If you do not, turn unit off and locate the short (either wiring to the Amp boards or something with the amp boards or outputs)

    Second, we need to see if there is DC coming from the Left or Right outputs. If there is, you have issues with the amp section of that channel.

    Third, is there approx. 14 volts after R553 (100K) on the board?

    Ill post a schematic that will help guide you
    MCS 3125 schematic 4.jpg
     
    Last edited: Nov 10, 2018 at 6:25 PM
  4. MCS Guy

    MCS Guy The MCS hoarder Subscriber

    Messages:
    540
    Location:
    FL
    Transistor outputs (2SD746/2SB706)
     
  5. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    All filter caps read 63v. Not sure where to measure outputs
     
  6. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    Because R553 is standing up and down to save space I can only read 1 side which is 63v
     

     

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  7. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
    3,138
    Location:
    El Sereno, CA
    Why did you replace the filter capacitors? If it's in protect it's likely got a problem on the amplifier board (shorted outputs, drivers, etc.) rather than the power supply.
    Resistors are fine to get hot if their job in the circuit is to drop a lot of voltage. My amp has a few that get over 120f but that's what they are there to do and they are within their rated wattage so no need for worry.
     
  8. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    Filters caps were bulging and leaking
    Worst set I have ever seen
    Ill post pics
     
  9. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    Ive read several threads on AK where replacing diodes and/or transistors on protect board was the issue. 2 of the resistors got so hot it melted the solder underneath
     
  10. MCS Guy

    MCS Guy The MCS hoarder Subscriber

    Messages:
    540
    Location:
    FL
  11. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    Will do
    And I do appreciate your help
    Thank you
     

     

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  12. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    I'm getting DC at those points
     
  13. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    image.jpg image.jpg Pic of caps. That isnt rust on the bottom cover. That's Cap juice
     
  14. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
    Fort Dodge, Iowa
    Those have definitely vented. Add those to your shopping cart.
     
  15. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
    Fort Dodge, Iowa
    Are those 6800µf/80v? What diameter and length are they?
     
  16. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    I may not have measured correctly
    You sent (2) photos of test points
    Am I measuring the (2) lugs in each photo?
    Or measuring (1) lug from each photo?
    OR. Each lug to ground
     
    Last edited: Nov 11, 2018 at 4:34 PM

     

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  17. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    35mm by
    80mm
     
  18. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
    Fort Dodge, Iowa
  19. Rex Runner

    Rex Runner BANG THY HEAD THAT WILL NOT BANG Subscriber

    Messages:
    353
    Location:
    Canton, Ohio
    Already replaced
    Had a set of 10,000uf on my shelf
    35mm by 50mm
    They work
     
  20. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
    Fort Dodge, Iowa
    That was handy..
     
    tater415 likes this.

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