Low Voltage To CCFL Tubes - Sony 55EX500

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  • max1636
    Senior Member
    • Dec 2013
    • 80
    • Australia

    #1

    Low Voltage To CCFL Tubes - Sony 55EX500

    Im currently waiting on an inverter board for a Sony 55EX500 TV but realized after working on another TV that the problem might actually be that the tubes aren't getting the right voltage. Reading each output to the CCFL tubes I get 175v AC. But on another Sony I was working on which is now functional the tubes are given 230v AC. Im going to open the TV up again tomorrow to see what voltage the PFC board is being given to investigate but I just wanted to know is 175v too low?
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: Low Voltage To CCFL Tubes - Sony 55EX500

    If you are using a digital multimeter to measure the tube outputs you've probably just destroyed the meter, as a 55" will drive tubes with about 3000V to start, 2000V to run.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

    Comment

    • max1636
      Senior Member
      • Dec 2013
      • 80
      • Australia

      #3
      Re: Low Voltage To CCFL Tubes - Sony 55EX500

      Originally posted by tom66
      If you are using a digital multimeter to measure the tube outputs you've probably just destroyed the meter, as a 55" will drive tubes with about 3000V to start, 2000V to run.
      I do it all the time and the multimeter is still fine. I have heard it's not recommended but its not a super expensive one its just a cheap model Fluke. So what you are saying is 175v is too low? The TV turns on for a few seconds and only dimmly shows the Sony logo on screen.

      Comment

      • Ltank
        Badcaps Veteran
        • Jun 2013
        • 776
        • USA

        #4
        Re: Low Voltage To CCFL Tubes - Sony 55EX500

        I just bought a Tenma H.V. Probe 1000:1 ratio can safety measure these voltages without damage to self or your DVM
        Last edited by Ltank; 12-29-2013, 09:01 AM. Reason: correct spellcheck

        Comment

        • max1636
          Senior Member
          • Dec 2013
          • 80
          • Australia

          #5
          Re: Low Voltage To CCFL Tubes - Sony 55EX500

          Originally posted by Ltank
          I just bought a Tenma H.V. Probe 1000:1 ratio can safety measure these voltages without damage to self or your DVM
          Thanks I might pick one of those up.

          Comment

          • tom66
            EVs Rule
            • Apr 2011
            • 32560
            • UK

            #6
            Re: Low Voltage To CCFL Tubes - Sony 55EX500

            I would not trust that meter after doing such a measurement. I haven't heard of any commercial portable battery powered meter capable of measuring beyond 1200V? 175V would only cause the ends of the bulbs to glow slightly...
            Last edited by tom66; 12-29-2013, 09:19 AM.
            Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
            For service manual, schematic, boardview (board view), datasheet, cad - use our search.

            Comment

            • selldoor
              Slow Learner
              • Dec 2010
              • 7870

              #7
              Re: Low Voltage To CCFL Tubes - Sony 55EX500

              Hi Tom -I have already told him that!! but even budm didnt pick up on it and neither did the the op.
              I am wondering if we are talking about the same transformers.

              For me an Inverter transformer is the one that connects directly to the
              ccfl socket.

              There are other transformers on the board that supply the inverter transformers
              so if the OP means one of those then 175v would be possible.

              Perhaps the OP can confirm exactly which transformer he is testing.
              Please upload pictures using attachment function when ask for help on the repair
              http://www.badcaps.net/forum/showthread.php?t=39740

              Comment

              • max1636
                Senior Member
                • Dec 2013
                • 80
                • Australia

                #8
                Re: Low Voltage To CCFL Tubes - Sony 55EX500

                Sorry guys I understand the reading I'm getting may not be correct but I thought it was weird that on one TV I was getting 230v AC and on another I was getting 175v AC. I was just wondering if that seems unusual? I will open the TV up today to test other voltages. Also the 175v AC and 230v AC reading I am getting from the test points going into the tubes from the inverter board.

                Comment

                • budm
                  Badcaps Legend
                  • Feb 2010
                  • 40746
                  • USA

                  #9
                  Re: Low Voltage To CCFL Tubes - Sony 55EX500

                  The AC of output of the inverter transformer can be from 60~100 KHz, the meter will not have the bandwidth to read that high AC frequency. It is also high impedance power source so the probe and the meter can easily load down the power supply.
                  Never stop learning
                  Basic LCD TV and Monitor troubleshooting guides.
                  http://www.badcaps.net/forum/showthr...956#post305956

                  Voltage Regulator (LDO) testing:
                  http://www.badcaps.net/forum/showthr...999#post300999

                  Inverter testing using old CFL:
                  http://www.badcaps.net/forum/showthr...er+testing+cfl

                  Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                  http://s807.photobucket.com/user/budm/library/

                  TV Factory reset codes listing:
                  http://www.badcaps.net/forum/showthread.php?t=24809

                  Comment

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