Samsung PN43F4500FXZA turns on no picture or sound

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  • nwelec
    Senior Member
    • Dec 2014
    • 61
    • usa

    #1

    Samsung PN43F4500FXZA turns on no picture or sound

    TV turns on I get proper VA of 58V but VS is 250V and should be 208V and I can not adjust it with the pot. Also voltages at CN4009 are correct when first turned on then they start to drop to 0. I can not find any thing online about this problem with this model and was hoping for some direction.
    Attached Files
  • Beau28713
    Senior Member
    • Feb 2018
    • 50
    • United States

    #2
    Re: Samsung PN43F4500FXZA turns on no picture or sound

    Remove pot and test pot for proper operation first. Then move on.

    Comment

    • R_J
      Badcaps Legend
      • Jun 2012
      • 9515
      • Canada

      #3
      Re: Samsung PN43F4500FXZA turns on no picture or sound

      What meter are you using to measure the Vs voltage, sometimes cheap meters react that way due to the high y drive pulses (lg/goldstar meters act that way)
      This may not be your problem but I thought I would mention it.

      You say the voltages on CN4009 are correct? pin 6 is the Vs pin, so it is 208v? then drops to 0
      Last edited by R_J; 06-20-2019, 05:42 PM.

      Comment

      • nwcs
        Badcaps Veteran
        • Dec 2015
        • 311
        • usa

        #4
        Re: Samsung PN43F4500FXZA turns on no picture or sound

        I use a Fluke 77 and have used fluke for 40 years. I will check the pot in the morning to see if it is defective. I will check pin 6 again tomorrow to see what it reads.

        Comment

        • R_J
          Badcaps Legend
          • Jun 2012
          • 9515
          • Canada

          #5
          Re: Samsung PN43F4500FXZA turns on no picture or sound

          I only mentioned the meter because I (and a couple others) have seen this, I normally use a Fluke but also have a cheap lg on the bench and on some plasma's, checking the Vs, even on 1000 volt scale will show OL. So I check with the Fluke and the reading is fine.

          Comment

          • nwelec
            Senior Member
            • Dec 2014
            • 61
            • usa

            #6
            Re: Samsung PN43F4500FXZA turns on no picture or sound

            So I tested both the pot which does adjust out of circuit and pin 6 of CN4009 which I thought was dropping but I found that it is steady at 250v but all other pins drop to 0v.

            Comment

            • R_J
              Badcaps Legend
              • Jun 2012
              • 9515
              • Canada

              #7
              Re: Samsung PN43F4500FXZA turns on no picture or sound

              That high voltage could be due to a lack of feedback to control the voltage, check the components around the control all the way to the optocoupler, I would also check on the primary side of the optocoupler. most power supplies go down in voltage when they loose feedback for safety
              Check that 0Ω off of DS853C, It supplies the low voltage for the feedback circuit on the secondary
              Last edited by R_J; 06-21-2019, 01:13 PM.

              Comment

              • nwelec
                Senior Member
                • Dec 2014
                • 61
                • usa

                #8
                Re: Samsung PN43F4500FXZA turns on no picture or sound

                Don't know how I missed this but there is corrosion all over the power supply board.
                Attached Files

                Comment

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