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VIZIO VO42L No picture, No Sound

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    #41
    Re: VIZIO VO42L No picture, No Sound

    I just got one of these and will be inspecting for the inverter problems. One question, how do I test the diodes, can they be tested in-circuit? My plan is to replace the BD9897FS chip and test the mosfets and replace all of them on the same board if one or more of them is bad. The caps I will also definitely replace with low leakage types.

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      #42
      Re: VIZIO VO42L No picture, No Sound

      Guys, I am not able to open this pdf for the inverter mods. Can anyone send it to me

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        #43
        Re: VIZIO VO42L No picture, No Sound

        it opens fine for me with foxit reader.free download.be sure to uncheck the dammed toolbar and homepage stuff though!
        Originally posted by geneg View Post
        Guys, I am not able to open this pdf for the inverter mods. Can anyone send it to me

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          #44
          Re: VIZIO VO42L No picture, No Sound

          Works now, thanks

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            #45
            Re: VIZIO VO42L No picture, No Sound

            Hello, I seem to be having a similar problem. The resistance was off on two mosfets so I replaced the IC on the slave board. Now they are all around 8.5k. The master board is at 8.5k as well.

            When turning the TV on, I get a backlight for about 2 seconds then it turns off again. Also, the blue light on the master board turns on, then off at the same time. Is that light supposed to be constant under normal operation?

            What else should I check?

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              #46
              Re: VIZIO VO42L No picture, No Sound

              Originally posted by b700029 View Post
              What else should I check?
              In the lcd computer monitor world, we normally ask people to check the resistance of the secondary inverter transformer pins. It should be within 3% of each other.

              Other possibles causes of 2 seconds to black in the lcd computer monitor world are:

              a) bad caps
              b) bad ccfl
              c) bad ccfl wiring (the return wire)
              Last edited by retiredcaps; 12-23-2011, 07:38 PM.
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                #47
                Re: VIZIO VO42L No picture, No Sound

                Originally posted by retiredcaps View Post
                Check the resistance of the secondary inverter transformer pins. It should be within 3% of each other.

                Other possibles causes of 2 seconds to black in the lcd computer monitor world are:

                a) bad caps
                b) bad ccfl
                c) bad ccfl wiring (the return wire)
                Can you explain which pins on the secondary inverter transformer?

                The backlight does light up fully for 2 seconds, does that rule out b) ?

                Oh, I forgot to add I also replaced both caps on each board. The caps on the Slave board were badly bulged so I replaced them and the IC at the same time.

                I'm guessing it has to do with the inverter boards, but I'm not sure how else to troubleshoot them. I'm also not sure if the blue LED is supposed to stay on or turn back off like I'm seeing.
                Last edited by b700029; 12-23-2011, 07:48 PM.

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                  #48
                  Re: VIZIO VO42L No picture, No Sound

                  Originally posted by b700029 View Post
                  Can you explain which pins on the secondary inverter transformer?
                  edit: Found a pic of the transformer with the pins identified.

                  http://lcdparts.net/TransformerDetai...ProductID=3898
                  Last edited by retiredcaps; 12-23-2011, 07:51 PM.
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                    #49
                    Re: VIZIO VO42L No picture, No Sound

                    Originally posted by b700029 View Post
                    The backlight does light up fully for 2 seconds, does that rule out b) ?
                    In the computer lcd world, the inverter pwm IC operates as "all or nothing". Either all ccfls work or none at all (shutdown after 2 seconds - various protection mechanisms kick in).

                    You can read more starting with post #19 at

                    https://www.badcaps.net/forum/showthread.php?t=10419

                    I'm also not sure if the blue LED is supposed to stay on or turn back off like I'm seeing.
                    The main TV power LED should stay on. I don't know about the master inverter board though.
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                      #50
                      Re: VIZIO VO42L No picture, No Sound

                      Originally posted by retiredcaps View Post
                      The main TV power LED should stay on. I don't know about the master inverter board though.
                      Yes, the LED on the front of the TV stays on. There is a separate blue one on the master inverter board I was wondering about.

                      Is this how I measure them?
                      Red probe on S1, black probe on S2
                      Red probe on P1, black probe on P2

                      Master inverter #1:
                      S-27.4 ohms
                      P-0.2
                      Master inverter #2:
                      S-27.5 ohms
                      P-0.2
                      Slave #1:
                      S-28.0 ohms
                      P-0.2
                      Slave #2:
                      S-28.1 ohms
                      P-0.2

                      The site you linked: S:56-59 ohms P:0.2-0.4 ohms
                      Last edited by b700029; 12-23-2011, 08:50 PM.

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                        #51
                        Re: VIZIO VO42L No picture, No Sound

                        Originally posted by b700029 View Post
                        Yes, the LED on the front of the TV stays on.
                        Okay, that is a good sign. That infers that the power supply and main/logic board are likely working.

                        There is a separate blue one on the master inverter board I was wondering about.
                        That one I don't know about. I'm assuming since the backlights are off, then it would be logical to have that blue light off as well.

                        Master inverter #1:
                        S-27.4 ohms
                        P-0.2
                        Master inverter #2:
                        S-27.5 ohms
                        P-0.2
                        Slave #1:
                        S-28.0 ohms
                        P-0.2
                        Slave #2:
                        S-28.1 ohms
                        P-0.2

                        The site you linked: S:56-59 ohms P:0.2-0.4 ohms
                        The above readings suggest that the inverter transformer is likely good even though the lcdparts.net site says 56-59 ohms.

                        Time to move onto testing the ccfls. Since it is unlikely you have a spare ccfl, do the test where you disconnect all but one. It is explained in post #20 in the troubleshooting guide.
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                          #52
                          Re: VIZIO VO42L No picture, No Sound

                          I noticed in post #21, that each inverter board has a SMD fuse. MF1 and SF2.

                          If there are 2 fuses and if one fuse is open, this may explain 2 seconds to black.

                          So check all your fuses on the boards to see if they are good or not. A good fuse should measure less than 1.0 ohms.

                          We had a similar case where one bad SMD fuse caused 2 seconds to black. From post #19 section 3 (of the troubleshooting guide) ...

                          https://www.badcaps.net/forum/showthread.php?p=197027

                          edit: This is why we always insist on clear focused pictures. Having those pics in post #21 help.
                          Last edited by retiredcaps; 12-23-2011, 09:20 PM.
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                            #53
                            Re: VIZIO VO42L No picture, No Sound

                            Originally posted by retiredcaps View Post
                            I noticed in post #21, that each inverter board has a SMD fuse. MF1 and SF2.

                            If there are 2 fuses and if one fuse is open, this may explain 2 seconds to black.

                            So check all your fuses on the boards to see if they are good or not. A good fuse should measure less than 1.0 ohms.

                            We had a similar case where one bad SMD fuse caused 2 seconds to black. From post #19 section 3 (of the troubleshooting guide) ...

                            https://www.badcaps.net/forum/showthread.php?p=197027

                            edit: This is why we always insist on clear focused pictures. Having those pics in post #21 help.
                            I can add photos, but post #21 was a good representation

                            Ok, checked MF1 on the master and SF2 on the slave and they were both <0.2 ohms. Both boards are seeing 24.5 volts too.

                            I will work on the CCFL test next, I read post #20 in your guide.

                            There is only one plug from each inverter board going into the panel. So that means I have to take it apart and there will be several CCFLs connected together to these two plugs that I can individually unplug? Or are there only two CCFLs? I saw another post that the inverter board had 10 or so plugs along the side of it, I can see how your idea works there.

                            Edit: I unplugged the output from the master board, and the backlight did not light for 2 seconds. Plugged in the master and unplugged the slave and it lights for 2 seconds. This could mean?
                            Last edited by b700029; 12-23-2011, 09:54 PM.

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                              #54
                              Re: VIZIO VO42L No picture, No Sound

                              Originally posted by b700029 View Post
                              I can add photos, but post #21 was a good representation
                              And post #4. I have to give credit to both posters for their pics.

                              Edit: I unplugged the output from the master board, and the backlight did not light for 2 seconds. Plugged in the master and unplugged the slave and it lights for 2 seconds. This could mean?
                              I can think of 2 things.

                              1) It could mean the master controls the whole show. That is, without the working master and its ccfls, nothing runs at all and it doesn't even try to light up the slave ccfls.

                              2) If the master doesn't control the whole show, then there is something wrong with the slave board and/or its ccfl/wiring.

                              Another test.

                              What happens if you plug the slave ccfl into the master board and vice versa using the same disconnect test?
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                                #55
                                Re: VIZIO VO42L No picture, No Sound

                                I agree there may still be a problem with the slave board. This is also the one I changed the IC on. (The MOSFET resistances are good now though).

                                Here is a photo of the back of the TV. I thought about trying to switch the boards but based on the wiring I don't think it would work. The master board has a 14p header from the PSU, while the slave has a 12p. The ribbon cables don't line up either.

                                With this arrangement can I not do your test of disconnecting all but one CCFL at a time?
                                Attached Files
                                Last edited by b700029; 12-23-2011, 10:11 PM.

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                                  #56
                                  Re: VIZIO VO42L No picture, No Sound

                                  Originally posted by b700029 View Post
                                  I thought about trying to switch the boards but based on the wiring I don't think it would work.
                                  I mean just switch the pink cables that go to the ccfls. You will have to do some board acrobatics so exercise caution and use cardboard to insulate and prevent shorts.

                                  Or are the cables all keyed towards a master and a slave?
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                                    #57
                                    Re: VIZIO VO42L No picture, No Sound

                                    Originally posted by b700029 View Post
                                    With this arrangement can I not do your test of disconnecting all but one CCFL at a time?
                                    I can't tell with the shielding how all the ccfls are arranged internally. Before you go taking things apart, there are a few more things to check on the inverter board and others may chime in with other suggestions.
                                    Last edited by retiredcaps; 12-23-2011, 10:59 PM.
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                                      #58
                                      Re: VIZIO VO42L No picture, No Sound

                                      Originally posted by b700029 View Post
                                      The resistance was off on two mosfets so I replaced the IC on the slave board.
                                      Can you post a picture of your slave board and circle which two you replaced? This will also identify what board revision you have.

                                      I'm wondering if you have to replace all 4 even if the 2 originals measured good resistance wise? A resistance test won't catch all the faults of the mosfet.
                                      Last edited by retiredcaps; 12-23-2011, 11:12 PM.
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                                        #59
                                        Re: VIZIO VO42L No picture, No Sound

                                        Originally posted by retiredcaps View Post
                                        I mean just switch the pink cables that go to the ccfls. You will have to do some board acrobatics so exercise caution and use cardboard to insulate and prevent shorts.

                                        Or are the cables all keyed towards a master and a slave?
                                        They are not keyed, but the cables are short and come out on opposite ends of the set. I think even with taking the power supply off so I can move everything over, the master board might not reach the slave plug.

                                        Ok, I will work on your suggestions and take more photos.

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                                          #60
                                          Re: VIZIO VO42L No picture, No Sound

                                          I am glad I found this site. I also have the VO42L FHDTV10A with sound and no picture.
                                          The "Vizio" logo changes from yellow to white and I am able to switch inputs and hear sound from the selected input, but I have no picture. Not even a dim picture.
                                          I was also concerned about the blue LED that is lit up on the master inverter but goes out 3 seconds after the tv is on.
                                          I will check the CCFL's tomorrow and switch out the IC on the master inverter.

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