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Panasonic TH-37PV500B poor vsync/colour after warming up

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    Panasonic TH-37PV500B poor vsync/colour after warming up

    Odd to see a plasma with Vsync issues!

    Got this one cheap as it's 37" 720p, was originally going to keep it for my bedroom but never got around to it... One of the smallest plasmas ever made, it's built like NASA engineered it because it's chock full of boards that manage to squeeze into such a small chassis. I count over 20 separate boards.

    Issue is with the picture: it's OK when cold, but the colours are wrong... they're solarised. As it warms up, the picture begins violently shaking up and down in two halves. Then, once it reaches a critical point, about an hour later, the picture starts getting better (colours are perfect) but still shakes a little.

    Accessing service menu is done by setting TREBLE to MIN, BASS to MAX in user menu, then pressing Index on the remote and VOL- on the TV. I selected test patterns and they're still distorted. Now I know most Panasonic plasmas do generate the test patterns on the D board but how to be sure? I pulled the LVDS from the D board, I get a little flicker from panel but the patterns stay up, and I can still cycle through them, I guess the control interface is on a separate cable. So, they must be generated by the D then, and since they're still distorted, it's probably a D board issue...

    I'm going to check the supplies/regulators on the D board but if they all check out, I'll just swap the D board as it's available for £15 postage included from eBay.
    Last edited by tom66; 10-20-2013, 10:32 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.

    #2
    Re: Panasonic TH-37PV500B poor vsync/colour after warming up

    Thats an odd one. I've always wanted to see inside the world's smallest consumer plasma tv.
    Did I leave the soldering iron on?

    Comment


      #3
      Re: Panasonic TH-37PV500B poor vsync/colour after warming up

      Now you can!

      Actually LG briefly, for one year, brought out a 32" 720p plasma. The LG 32PG6000. Very odd decision on their part; I don't think it was a big seller, but I've always wanted one to have a look at. There's also evidence that LG considered a 37 inch panel and prototyped it, but never sold one; the UL documentation showed they had one rated (the PDP37R1xxxx.) Also Samsung around 2002 had a 37" 480p plasma but for OEM use only.

      I cable tied the PB board to get it out of the way; there are boards on top of boards on top of boards on this model! The Freeview/DVB board was removed to get to the DG board, this obviously disabled Freeview but also oddly stops the TV turning off fully. Just sits there with glowing screen if you press power off, until you unplug it.

      And yes despite only being 37 inches it has fans... Power rating over 350W.
      Attached Files
      Last edited by tom66; 10-20-2013, 10:48 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


        #4
        Re: Panasonic TH-37PV500B poor vsync/colour after warming up

        Pictures of the fault.
        All taken at approx same time -- the fault intensity varies with picture brightness.
        Attached Files
        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


          #5
          Re: Panasonic TH-37PV500B poor vsync/colour after warming up

          Wow that tv is packed! I thought the sony kde-50xs955 was bad. Lol.
          Did I leave the soldering iron on?

          Comment


            #6
            Re: Panasonic TH-37PV500B poor vsync/colour after warming up

            What happens if you hit the MN84512 GPU with freeze spray?
            Did I leave the soldering iron on?

            Comment


              #7
              Re: Panasonic TH-37PV500B poor vsync/colour after warming up

              Originally posted by freakaftr8 View Post
              What happens if you hit the MN84512 GPU with freeze spray?
              Tried already, no noticeable change.
              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


                #8
                Re: Panasonic TH-37PV500B poor vsync/colour after warming up

                All regulators test OK.
                5V in to board is 4.77V, but this is immediately regulated to the lower voltages.
                12V is also a bit low at 11.75V.
                3.3V, 2.5V, 1.5V all good.

                Going to test crystal now, if that test OK then I will call it a day and order the board.
                Last edited by tom66; 10-20-2013, 01:22 PM.
                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


                  #9
                  Re: Panasonic TH-37PV500B poor vsync/colour after warming up

                  New D board in... but no luck. Same problem. I thought I had narrowed it down. I'll have to check a few more things. Something about the flickering looked different, hard to put my finger on it... could be there's some change but not sure. Cannot rule out a defective replacement board, so will question eBay seller as to how it was tested.
                  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

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