Magnavox 42MF230A/37-No picture or sound

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  • KTMLew
    Member
    • Sep 2011
    • 37
    #1

    Magnavox 42MF230A/37-No picture or sound

    Bought this as a project. Seems it's a boondoggle...

    Removed all boards and inspected for cold solder joints, bulged caps, twisted testicles, etc...

    When plugged in power button turns Red.

    When power button pressed it turned Blue and one relay on sub-power supply would click. Could not shut-down w/o disconnecting power. Found the main PS (large board) was only powering up primary side.

    After much reading/testing replaced PS (large board) and it then powered up/shut down normally. No picture or sound. No response to any buttons pressed on control panel except for start-up/shut-down. Don't have the remote. All voltages (ve,ve,vscan,etc) with in acceptable ranges. Unplugged Y & X sustains. Still no picture or sound.

    Found that 3 caps have been replaced on original main PS (large board) and 1? on Y sustain. Tested buffers per Coppell TV's rec. Need to do again but think both are bad...am posting from internet cafe due to home internetz being down...

    My question is...can the buffers be repaired and/or can the plasma panel be tested BEFORE I dump more money in it? Approaching $150.00 invested and figure $300.00 would be absolutely the limit...but an education is priceless...right?

    I will take some pictures tonight just for shits & giggles...do you want me to wear anything special?
    Last edited by KTMLew; 09-10-2011, 01:04 PM.
    Tags: None
    • KTMLew
      Member
      • Sep 2011
      • 37
      #2
      Re: Magnavox 42MF230A/37-No picture or sound

      Should have apologized in advance for not having any real voltage readings to post...my leads won't reach all the way home...I'll do better next time, I promise.

      Some notes would be appropriate...

        Comment

        • PlainBill
          Badcaps Legend
          • Feb 2009
          • 7034
          • USA
          #3
          Re: Magnavox 42MF230A/37-No picture or sound

          Here's the situation. As I recall, the buffer ICs are about $10 each. There are 100 pin ICs, so replacing them is somewhat of a chore. With the proper hot air equipment it could be a 5 minute job, with ChipQuik to remove the buffer and a fine tip soldering iron and a steady hand to solder in the new one it could turn into an hour long job.

          The driver FET on the Y-sustain is an different matter. They are available for about $7 each. Since they are mounted very closely together I have no idea how to remove them without the proper hot air equipment. Installing the new one should be relatively easy.

          NOW you come to the next problem - testing. Remember, when a buffer IC shorts, it may damage another buffer IC. If that happens, the second IC will short when power is applied. And that will take out a fet on the Y-sustain. I have heard rumors of a modification to the Y-sustain that will protect the FETs, but have no idea of what it is.

          My suggestion is to write this project off as a learning experience. It is uneconomical to repair the TV.

          PlainBill
          For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

          Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

            Comment

            • KTMLew
              Member
              • Sep 2011
              • 37
              #4
              Re: Magnavox 42MF230A/37-No picture or sound

              Thanks for the quick response. Finding plenty of broken screen plasmas & LCD's locally that may be a donar TV. Lots of others with start-up issues that may just be caps. I'm 100% new to TV component repair so learning as I go. Was just hoping to fix this for my own use. Probably sell it to a local TV repair shop if they want it for parts.

              Again thanks...I was fairly sure that would be your response!

                Comment

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