Vizio VX32L No picture, sound, or backlight

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  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #41
    Re: Vizio VX32L No picture, sound, or backlight

    Oh, I initially said the CPU survived it... But maybe it got damaged?
    Try on HDMI. If that works, the analogue part of the chip is shot -- no analogue sources will work.
    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

    • johnboy1313
      Badcaps Legend
      • Nov 2012
      • 1959
      • USA

      #42
      Re: Vizio VX32L No picture, sound, or backlight

      Well, I'm pretty sure my issue has something to do with a fried or damaged board. At the new regulator, I'm getting

      3.29
      1.65
      1.25

      I disconnected the adjust jumper from the board and get the same readings. With the jumper disconnected, I get the same results with the video input. Either I'm not getting the adjust pin connected to the board properly, or the board is fried.

      What do you guys think?
      Last edited by johnboy1313; 11-25-2012, 07:16 PM.

      Comment

      • johnboy1313
        Badcaps Legend
        • Nov 2012
        • 1959
        • USA

        #43
        Re: Vizio VX32L No picture, sound, or backlight

        Originally posted by tom66
        Oh, I initially said the CPU survived it... But maybe it got damaged?
        Try on HDMI. If that works, the analogue part of the chip is shot -- no analogue sources will work.
        I've only got one HDMI component and that won't work on the 720p units. AVG is analog isn't it?

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #44
          Re: Vizio VX32L No picture, sound, or backlight

          It should have 2.5V out put if the adjust pin is at 1.25V. It can due to it is not LDO regulator.
          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

          • johnboy1313
            Badcaps Legend
            • Nov 2012
            • 1959
            • USA

            #45
            Re: Vizio VX32L No picture, sound, or backlight

            Originally posted by budm
            It should have 2.5V out put if the adjust pin is at 1.25V. It can due to it is not LDO regulator.

            Unfortunately, I don't know enough about regulators to know what you are saying.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #46
              Re: Vizio VX32L No picture, sound, or backlight

              This is the way to figure out if the adjustable regulator is good or not:
              Notes: we are looking at the regulator with the Big tab up (the big tab is tied internally to the center pin).
              Adjustable regulator will have two resistors attached to it, one resistor (Rfb) is between pin1 and pin2, another resistor (Rg) is between pin1 and ground. Pin3 is an input pin.
              The voltage between the Adjust pin (left pin) and the center pin (Pin2, output) will always be 1.25V +/- 2% (this is the precision voltage reference), if it is not, it is bad.
              To figure out what the output voltage should be: measure the voltage between pin 1 and ground and add 1.25V to that number, that is the output voltage on pin 2 but you have to make sure you do have 1.25 between pin 1 and 2 as noted above
              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

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #47
                Re: Vizio VX32L No picture, sound, or backlight

                ADJUST must be grounded. The regulator will then output 1.25V, but only if it is loaded sufficiently (it requires minimum of about 10mA to regulate.) To ensure it is loaded tie a 120 ohm resistor to ground.

                The output of all adjustable LDOs, as well as adjustable linear regulators, is Adjust+1.25V.
                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

                • johnboy1313
                  Badcaps Legend
                  • Nov 2012
                  • 1959
                  • USA

                  #48
                  Re: Vizio VX32L No picture, sound, or backlight

                  So, with the adjust disconnected, I should have 1.25V at the out. And if I don't, the regulator is bad? If I do, the board, or at least the analog section of the board is shot?

                  Comment

                  • tom66
                    EVs Rule
                    • Apr 2011
                    • 32560
                    • UK

                    #49
                    Re: Vizio VX32L No picture, sound, or backlight

                    No, not disconnected. It MUST be grounded.
                    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

                    • johnboy1313
                      Badcaps Legend
                      • Nov 2012
                      • 1959
                      • USA

                      #50
                      Re: Vizio VX32L No picture, sound, or backlight

                      Got it. Out of curiosity, why a 120 ohm resistor? Why not jut tie it to ground?

                      Comment

                      • johnboy1313
                        Badcaps Legend
                        • Nov 2012
                        • 1959
                        • USA

                        #51
                        Re: Vizio VX32L No picture, sound, or backlight

                        Never mind, I see. Current draw?

                        Comment

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #52
                          Re: Vizio VX32L No picture, sound, or backlight

                          120 ohms must go to ground from the output. This provides 1.25/120 = 10.4mA current draw, which is within the minimum specified.

                          So the INPUT goes to 3.3V or 5V, depending on which works.
                          The OUTPUT goes to the OUTPUT of the ex-regulator.
                          The ADJUST goes to GROUND.

                          A capacitor of 100nF minimum is required on the output. Input capacitance is also a good idea.
                          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

                          • johnboy1313
                            Badcaps Legend
                            • Nov 2012
                            • 1959
                            • USA

                            #53
                            Re: Vizio VX32L No picture, sound, or backlight

                            I'm getting the 3.3 off the resistor that originally supplied it to the damaged regulator pad. The output is jumped back to the original spots too. I'm going to try to ground the adjust. I don't have a 120 ohm resistor, but I do have a 1k potentiometer adjusted down to 120 ohms. If it works, I'll pick up an actual resistor tomorrow.

                            Comment

                            • tom66
                              EVs Rule
                              • Apr 2011
                              • 32560
                              • UK

                              #54
                              Re: Vizio VX32L No picture, sound, or backlight

                              You can use a lower value, but probably no lower than 10 ohm, as it would have to dissipate a lot of heat. (10 ohm = 0.144W; maximum for a 1/4W resistor is... 1/4W or 0.25W.)
                              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

                              • johnboy1313
                                Badcaps Legend
                                • Nov 2012
                                • 1959
                                • USA

                                #55
                                Re: Vizio VX32L No picture, sound, or backlight

                                Well, the good news is the regulator works like it's supposed to. The bad news is there's still no video signal.

                                So going back to an earlier question. Does the 4a, 4b suffix on the main board part number make a difference?

                                Comment

                                • budm
                                  Badcaps Legend
                                  • Feb 2010
                                  • 40746
                                  • USA

                                  #56
                                  Re: Vizio VX32L No picture, sound, or backlight

                                  There should be existing resistors between the ADJ and OUT pin, and Adj and ground, unless those tiny resistors got damaged or removed during the installation of the replacement LDO.
                                  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

                                  • johnboy1313
                                    Badcaps Legend
                                    • Nov 2012
                                    • 1959
                                    • USA

                                    #57
                                    Re: Vizio VX32L No picture, sound, or backlight

                                    Originally posted by budm
                                    There should be existing resistors between the ADJ and OUT pin, and Adj and ground, unless those tiny resistors got damaged or removed during the installation of the replacement LDO.
                                    Yeah, the adjust resistor must have gotten damaged.

                                    Comment

                                    • johnboy1313
                                      Badcaps Legend
                                      • Nov 2012
                                      • 1959
                                      • USA

                                      #58
                                      Re: Vizio VX32L No picture, sound, or backlight

                                      Originally posted by johnboy1313
                                      So going back to an earlier question. Does the 4a, 4b suffix on the main board part number make a difference?
                                      Doesn't matter, the board sold.

                                      Comment

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