Sony KDL46SL140 - Works when hot, doesn't work when cold

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  • marls
    New Member
    • Sep 2012
    • 6
    • USA

    #1

    Sony KDL46SL140 - Works when hot, doesn't work when cold

    TV: Sony Bravia KDL46SL140

    If the TV is over 90 degrees warm, it works just fine, no problems.

    If the TV has an ambient temperature in the 70's or 80's it shuts off during some kind of power on self test. I see the Bravia logo appear on the TV but before I get any control of the TV (within 6 seconds) the relay switches the TV off. It will stay off until I unplug it and plug it back in.

    I've taken the back off and looked for swollen caps. I didn't see any obvious ones. I also used my magnifying glass to look for bad solder joints. Again I couldn't spot any.
    Since the TV has 3 main electrical boards I wanted to narrow down which board it was. I proceeded to heat up only 1 board at a time to see if I could get the TV working with just 1 board being hot. I tried this for 2 of the boards but even with the boards being hot the TV didn't stay on.

    I'm not sure what to really try next. Has anyone gone through something like this before that can offer some further advice?
    Thanks!
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

    Have you tried reseating all connectors to see if it could be a loose one?

    Try removing the power supply board and checking for cold/cracked solder joints on the bottom of the PSU board. A bad solder joint looks like this:

    http://home.comcast.net/~tatng/Auto/...cked-joint.JPG
    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

    • marls
      New Member
      • Sep 2012
      • 6
      • USA

      #3
      Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

      There are 3 main circuit boards in this TV. I'm not an expert, but one is where the power cable is terminated to which I believe is the PSU, one is where all the AV components plug in to, and another is probably a LCD controller bank.

      Today I took the TV outside to warm it up. It worked fine. I took out the PSU and AV board and put them in the freezer for 10 minutes. I brought them out and put them in the TV and it worked fine. This proves to me that neither the PSU or the AV board are the problem here.

      What else can I look for? Should I do the same with the LCD controller? Should I take out the board that has the power/volume button control? Should I take out the board that has the IR receiver/Status LEDs? Perhaps this is a connector that works when hot. Perhaps the florescent light doesn't work when cold?

      Comment

      • marls
        New Member
        • Sep 2012
        • 6
        • USA

        #4
        Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

        Attaching picture of back of set. The two boards that seem to be ok when hot or cold is the orange one in the center and the blue one on the bottom right.
        Attached Files

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

          Can you remove the orange board (PSU) and try resoldering any joints that look dodgy... like this: http://homepage.ntlworld.com/michael...Solder%201.jpg

          If that's OK, then the problem is possibly on the main board (blue one.)
          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

          • marls
            New Member
            • Sep 2012
            • 6
            • USA

            #6
            Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

            Tom66, sorry for being a dork but, I feel like I've proved that the PSU and main board don't have a problem because they work both hot or cold. Looking for dodgy joints on those doesn't make sense to me. Can you explain?

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

              Completely my mistake, I misread your post. So, are you saying when you heat up that board the main board connects to, at the top of the LCD panel, the TV works? That is the T-con board.
              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

              • marls
                New Member
                • Sep 2012
                • 6
                • USA

                #8
                Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

                I believe I have found the problem! The board on the far left which I think is the florescent bulb driver board is definitely the problem. When the entire TV is cool but that board is hot, the TV works.

                Upon examining this board I see some melted plastic pieces. I believe this is where the problem is but I don't know how to fix it yet. The plastic doesn't come off very easily to see what is under it. Attached are photos. Suggestions would be great at this point on how to fix the melted area!
                Attached Files

                Comment

                • tom66
                  EVs Rule
                  • Apr 2011
                  • 32560
                  • UK

                  #9
                  Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

                  Yes, that is the ballast board. This PSU is similar to Samsung and LG, but different from most other TVs, in that it generates one high voltage (approx 3000V) which is distributed to all the bulbs individually. Normally one voltage is generated for each. The black things (transformers) balance the current between each bulb and detect faulty bulbs. I suggest all you have is an intermittent contact, the arcing 3000V has burnt the connector. Use a scourer to clean off the surface and make sure the contact is properly cleaned. Reseating it too, as well as tightening the screws on the ballast board, could help.
                  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

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

                    SONY calls this Balancer board, it works as TOM said. I can see at least 3~4 more in pix #3 that the black plastic pieces are deforming. You should remove the board and clean the copper pads on the board real well with an eraser and then clean them with Alcohol. Clean off any carbon tracks that you can see also.
                    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

                    • ben7
                      Capaholic
                      • Jan 2011
                      • 4059
                      • USA

                      #11
                      Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

                      WOW that is a big fire hazard!
                      Muh-soggy-knee

                      Comment

                      • marls
                        New Member
                        • Sep 2012
                        • 6
                        • USA

                        #12
                        Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

                        TV works great now. I cleaned the contacts just as suggested and now there is no buzzing or arcing. Thanks guys!

                        Comment

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #13
                          Re: Sony KDL46SL140 - Works when hot, doesn't work when cold

                          Glad to hear you fixed it! A very strange one indeed. Bud have you seen this before?
                          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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