Panasonic TX-L55WT50B

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  • comptek
    Badcaps Veteran
    • Aug 2013
    • 606
    • uk

    #1

    Panasonic TX-L55WT50B

    Hi guys hope you are all well
    Hoping there are some Panasonic specialists about I have the above model
    Tx-l55wt50b I have looked for a schematic of the power supply and couldn’t find one even the service manuals only cover everything else but the psu.
    Anyway I got the tv and it was making a loud buzzing noise from the back opened it up and found that IC571 / 2A fuse / a couple of zeners on the back had blown

    Power supply CT31004 U84PA-E0011754B

    Replaced IC571
    Replaced fuse with a temp 2A wire
    I had zeners in place but probably wrong as when I plugged it in all that happens is the red light flashes 3 times pause 3 times pause and so on.....

    Position ZD571 was a G5 zener I think I found an equivalent?
    Position ZD572 Empty had a zener there that was short
    Position ZD552 Found to be shorted too

    Can anyone point me in the right direction of the values/ Equivalent or a manual for the power supply

    Thanks in advance

    Gary
    Last edited by comptek; 03-19-2021, 05:56 AM.
  • comptek
    Badcaps Veteran
    • Aug 2013
    • 606
    • uk

    #2
    Re: Panasonic TX-L55WT50B

    Here are some photos
    Attached Files

    Comment

    • R_J
      Badcaps Legend
      • Jun 2012
      • 9514
      • Canada

      #3
      Re: Panasonic TX-L55WT50B

      A 3 blink sos refers to an "A" board fault, Was there a number on IC571?
      Last edited by R_J; 03-19-2021, 07:44 PM.

      Comment

      • comptek
        Badcaps Veteran
        • Aug 2013
        • 606
        • uk

        #4
        Re: Panasonic TX-L55WT50B

        Hi RJ, there was a number that I had to clean off the black glue to find and piece together it was FSFR1700XSL I purchased two just in case...
        I need to get the power supply back to standard before I can test anything else
        When I got the 3 flashes i set out to find some zener diodes, it was then when I took the diode off of the lower side to test it that I found it it was short so that may have caused the 3 flash sos

        Comment

        • comptek
          Badcaps Veteran
          • Aug 2013
          • 606
          • uk

          #5
          Re: Panasonic TX-L55WT50B

          Hi guys any other help available
          Schematic diagram of power supply?
          Approx values of zeners ?

          Thanks in advance
          Gary

          Comment

          • Diah
            Badcaps Legend
            • Feb 2013
            • 6341
            • Germany

            #6
            Re: Panasonic TX-L55WT50B

            f you upload a complete photo of yours PSU from both side. and remark the area you have short on it will be more essential, because from my know early Panasonic TV PSU used same main diagram to build any further versions. so any early Panasonic psu boards will give the answer on any missing mysteriously parts.

            Comment

            • R_J
              Badcaps Legend
              • Jun 2012
              • 9514
              • Canada

              #7
              Re: Panasonic TX-L55WT50B

              I'm not sure if this will help, but this Samsung power supply uses the same ic. The BN44-00498A uses it as well.
              The ZD572 seems to be between Lvcc and ground, so I suspect it is just for over voltage protection. IC lvcc max is 25v so it could be a 18~20v zener
              ZD573 is on the CS, current sense line to ground, this pin sees a very low negative voltage so I would guess a zener of around 4.7v or maybe less?
              Attached Files
              Last edited by R_J; 03-21-2021, 01:19 PM.

              Comment

              • comptek
                Badcaps Veteran
                • Aug 2013
                • 606
                • uk

                #8
                Re: Panasonic TX-L55WT50B

                Hi guys I fixed it
                I replaced the faulty zener diodes with what work out to be 4.5v ish and it's working now all there was 3.2volt and 5 volt that was all
                Now all voltages are up
                Crikey wow what a picture on it I'm going to run it for a couple of days
                Attached Files

                Comment

                • R_J
                  Badcaps Legend
                  • Jun 2012
                  • 9514
                  • Canada

                  #9
                  Re: Panasonic TX-L55WT50B

                  Are you sure you used a 4.5v zener for ZD572 & ZD552? That is the Lvcc line and should be around 12 volts
                  I can see 4.5v for ZD573 & ZD553 but not ZD572 or ZD552
                  Last edited by R_J; 03-22-2021, 10:41 AM.

                  Comment

                  • comptek
                    Badcaps Veteran
                    • Aug 2013
                    • 606
                    • uk

                    #10
                    Re: Panasonic TX-L55WT50B

                    Originally posted by R_J
                    Are you sure you used a 4.5v zener for ZD572 & ZD552? That is the Lvcc line and should be around 12 volts
                    I can see 4.5v for ZD573 & ZD553 but not ZD572 or ZD552
                    I will double check R J but it's been on all day I keep switching it off and back on and it seems fine at the moment

                    Regards
                    Gary

                    Comment

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