Sansui STY0440 cemfets hot/ failure?

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  • Grunder
    Badcaps Veteran
    • Jan 2016
    • 323
    • south africa
    #1

    Sansui STY0440 cemfets hot/ failure?

    Hi Guys,

    This television came in without a picture two weeks back. It was switching on with the led going from red to blue.

    The 24v & Blon were present, so I took the inverter pcb out to check for shorts.

    The invertor pcb divides the 24v to two banks of cemfets. One of the 7amp fuse's suppling one of the banks was open, with a dead short on that particular bank of cemfets. (AO4614B)

    I replaced Q321 AO4614B with an AO4614. (no B)

    The specs' show the AO4614B capable of handling 30amps pulsed drain current, the AO4614 20amps pulsed drain current.

    The set has come back with Q321 short & fuse blown again. (obviously weaker)
    I've replaced with the same AO4614. (No AO4614B on hand & cust eager)

    Why after running awhile do all the cemfets get very hot?
    (can't believe some thing so small can endure this heat) see photo

    Busy trying to source the AO4614B.

    It is an old Lcd, and I'm sure the panel has seen many hours.
    Should I replace all of them in one go, or one at a time as they fail??
    Seems like a silly question, I just need some input please.
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    Tags: None
    • ReeceyBurger123
      Never Give Up !
      • May 2014
      • 7325
      • Britain
      #2
      Re: Sansui STY0440 cemfets hot/ failure?

      Watch my vid matey on the SSI-400-14A01 buddy you need to resolder lots of SMD parts that can cause the fets to blow as well as the SEM2071 or whatever it is.
      Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

      https://www.facebook.com/Telford-Tel...7894576335359/

        Comment

        • ReeceyBurger123
          Never Give Up !
          • May 2014
          • 7325
          • Britain
          #3
          Re: Sansui STY0440 cemfets hot/ failure?

          Infact Im in such a nice mood I will save you the effort watch this:

          https://youtu.be/2QTfOy4BUpU
          Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

          https://www.facebook.com/Telford-Tel...7894576335359/

            Comment

            • Grunder
              Badcaps Veteran
              • Jan 2016
              • 323
              • south africa
              #4
              Re: Sansui STY0440 cemfets hot/ failure?

              Originally posted by ReeceyBurger123
              Infact Im in such a nice mood I will save you the effort watch this:

              https://youtu.be/2QTfOy4BUpU
              Thanks Reecey, grand of you, I was about to ask how to get there, Thanks.
              I've had 3 returns on the same day, so not so grand this side. Will post other 2.

                Comment

                • Grunder
                  Badcaps Veteran
                  • Jan 2016
                  • 323
                  • south africa
                  #5
                  Re: Sansui STY0440 cemfets hot/ failure?

                  Thanks again Reecey. Identical set in clip as mine. Now to try source new chips.
                  I had ripped second hand ones off another board.

                  Is there a reference library of sorts that would have led me straight to the clip on utube? or would I have had to go through all the clips to get there?
                  I'm an old dawg (almost 60), and not so clued up as you young 'uns.

                    Comment

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