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Toshiba 42ZV635D not powering on

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    #1

    Toshiba 42ZV635D not powering on

    Hi there,
    got this TV not powering on. Checked PSU, seems to be ok but not turning on the LCD 24V. Red LED in front is not turning green. 5V Standby, 18V, 12V and 24V to the main board is ok. P-Protect and AC-Det is around 3,2V. Do not see P-Sig and P-LCD (zero volts). Do not hear the Relay clicking. I don't have the schematics of the power board but found that 12V LCD and 24V LCD will be activated by P-LCD. Unfortunately the powerboard is not part of the documentation available at elektrotanya.com.
    Before I poke into the mainboard why it does not activate the LCD - anyboady out there with some experience?
    Power Board is SRV2194WW. Main board is V28A000966B1 or PE0693 (not shure what is the right number).
    Any help would be really appreciated.
    Martin
    Tags: None
    #2
    Re: Toshiba 42ZV635D not powering on

    Can we see good clear pictures of all the boards and how they are connected together?
    It sounds like the main board is not sending the command signals.
    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

      #3
      Re: Toshiba 42ZV635D not powering on

      Shure, see following pictures. I already checked the capacitors in the main supply lines. All of them seem to be in a normal range. What I also saw: It does not power on the supply for the audio on the main board.

      Got the description from the former owner that the TV could not be switched off for some reasons. After a while it was also not possible to switch it on. There may be a corrupted EEProm which is often mentioned in the forum? Or maybe a power rail on the main board failed.





      Attached Files
      Last edited by mslr; 11-02-2017, 04:28 AM.

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        #4
        Re: Toshiba 42ZV635D not powering on

        Any ideas?

        Comment

          #5
          Re: Toshiba 42ZV635D not powering on

          Well, first I'd try freezing the EEPROM with a can of air upside down and turn the TV on. Sounds like a main board problem. See what happens...
          PSon and BLon are created on the main board. Could also be that the main IC needs a reflow, or it may be toasted.
          Last edited by CapLeaker; 11-06-2017, 02:20 PM.

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            #6
            Re: Toshiba 42ZV635D not powering on

            A can of cold air is one way to test it.

            Another way to test it is with a hot air gun. try heating the caps powering the gpu. or heating the GPU its self with about 220F. this will not be hot enough to 'reflow" the balls under it.but it will be enough to make the wires ans balls hot enough to make the wires touch the balls in the gpu.
            Disclaimer: Don't trust a thing I say-I am frequently wrong!!!

            I have tons of spare parts, some used, some N.O.S. ham transistors and caps. Message me if you need any parts.

            Some of the things I've fixed:
            60" Vizio-bad LED's. iBook G4: Resoldered VCC Plug. Geo Tracker ECU: Swollen / Leaking capacitors. Windows Laptop: Soldered broken LVDS wires. Dryer: Burned contact on temp switch. Oven in R.V.: Bad contacts in relays-Exploded by the looks of them! Samsung Oven: Burned contacts on Relays. MSI Motherboard: BSOD-Swollen capacitors, bad graphics card, Moved SATA Input from SATA 1 to SATA 2 plug

            Comment

              #7
              Re: Toshiba 42ZV635D not powering on

              If you have no idea what I mean: then do not touch it, and take it to a professional.
              Disclaimer: Don't trust a thing I say-I am frequently wrong!!!

              I have tons of spare parts, some used, some N.O.S. ham transistors and caps. Message me if you need any parts.

              Some of the things I've fixed:
              60" Vizio-bad LED's. iBook G4: Resoldered VCC Plug. Geo Tracker ECU: Swollen / Leaking capacitors. Windows Laptop: Soldered broken LVDS wires. Dryer: Burned contact on temp switch. Oven in R.V.: Bad contacts in relays-Exploded by the looks of them! Samsung Oven: Burned contacts on Relays. MSI Motherboard: BSOD-Swollen capacitors, bad graphics card, Moved SATA Input from SATA 1 to SATA 2 plug

              Comment

                #8
                Re: Toshiba 42ZV635D not powering on

                Checked the schematics. The microcontroller who does the control is a QFP64 Package. Sorry, no balls to reflow. Checked the power rails on the main board. Two of them are missing. The switching regulators do not geht their enable signal generated by the micro. Freezing the EEProm does not change anything. Found two of them on the board and cooled both down without any change. Maybe the microcontroller is missing a signal to go ahead. Where to go next? Reading the EEProm? Which signals must be present to start powering up?

                Comment

                  #9
                  Re: Toshiba 42ZV635D not powering on

                  I do board level repair (Apple Macbook and iPhones) just for fun. So everything is available to do it in a professional way. I can measure what you request to point in the right direction.

                  Comment

                    #10
                    Re: Toshiba 42ZV635D not powering on

                    Just a note about freezing the eeprom, freeze it before pluging in the tv.
                    unplug the tv, freeze the eeprom, plug in the tv then try turning it on.

                    Comment

                      #11
                      Re: Toshiba 42ZV635D not powering on

                      Did that exactly in that order. Still no change in behaviour.

                      Comment

                        #12
                        Re: Toshiba 42ZV635D not powering on

                        that sux... guess you need a new main board then.

                        Comment

                          #13
                          Re: Toshiba 42ZV635D not powering on

                          Will not give up that easy. It’s fun to reverse engineer a TV and not to exchange a board.

                          Comment

                            #14
                            Re: Toshiba 42ZV635D not powering on

                            Ok found a shorted power rail which is shorted by one of the big BGAs. Not worth to repair. Taking your suggestion and looking for a board. BTW: took out the EEProm and read it frozen and warmed up. Same values. Defenitely it is not the EEProm.

                            Comment

                              #15
                              Re: Toshiba 42ZV635D not powering on

                              Usually that's how it always ends after one ruled out the easy stuff.

                              Comment

                                #16
                                Re: Toshiba 42ZV635D not powering on

                                Checked all the capacitors by putting them off an after measuring again on in the power rail and ended up that the big BGA is shorted. To repair that I will need a BGA rework station and a known good chip. Got a spare board for about 50$.

                                Do I need the content of the EEProm to adjust the new board?

                                Comment

                                  #17
                                  Re: Toshiba 42ZV635D not powering on

                                  nope

                                  Comment

                                    #18
                                    Re: Toshiba 42ZV635D not powering on

                                    Ok, after changing mainboard TV is back to live. Will test everything in the next days. Thx for support, appreciate!

                                    Comment

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