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    #1

    Vizio SV47OXVT1A Will n0ot power on

    Vizio SV47OXVT1A While watching the TV the sound became very distorted, for a minute or so and then the TV shut down. Now it will not power on. I do not hear a click when I plug it in or push the power button.
    I have no voltage out of the power supply except for the 5.5Vdc at the stand by. I checked voltages regulators on the AV main board with the following results
    U20 V1, 2.75, VO, 1.25
    U15 VI 2.95 VO 1.25
    U16 nothing in or out
    U21 VI 2.5 VO 1.26
    U19 VI 3.77 VO 1.25

    I have checked all the fuses and they are good.
    In the first photo the middle fuse is good but no voltage to it
    The second photo I have no voltage in or out of two regulators
    Photo 3 the connector to the power button, channel and volume control, and input
    Blk Wire 3.26
    Brown 3.8
    Red 5.12
    Orange 5.12
    yellow 1.4
    Green 0
    Blue 0
    Violet 2.2, but only when the power button is pused in and held in
    Gray 0
    White 3.3

    By the syptoms I was first thinking Main AV board but with no power at the outputs of the power supply has me cornfused,,,, does the Main AV board turn on sections of the power supply? All the diodes on the power supply tested good. No bulging caps, dark or burnt spots on the boards.
    Main AV board CSD: 3647-0102-0395
    Power Supply DPS 379AP A
    Attached Files
    Tags: None
    #2
    Re: Vizio SV47OXVT1A Will n0ot power on

    Originally posted by shorteddiode View Post
    I checked voltages regulators on the AV main board with the following results
    U20 V1, 2.75, VO, 1.25
    U15 VI 2.95 VO 1.25
    U16 nothing in or out
    U21 VI 2.5 VO 1.26
    U19 VI 3.77 VO 1.25
    See my sig file below on how to test and report the voltage regulators. Without part numbers, we can't tell if they are good or bad.

    BTW, I count at least 7 regulators and 5 fuses on the main board.

    By the syptoms I was first thinking Main AV board but with no power at the outputs of the power supply has me cornfused,,,, does the Main AV board turn on sections of the power supply?
    The main board is responsible for turning on the secondary power supply outputs via PS_ON pin. It will generally toggle the pin "high" or > 3V.
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    Comment

      #3
      Re: Vizio SV47OXVT1A Will n0ot power on

      I found 6 regulators am I missing one. All 5 fuses test good with a continuity tester

      U20 pcb designation
      Line 1 0811KL
      Line 2 1084
      Pin 1 .558V
      pin 2 1.81V
      pin 3 3.30V

      U15 pcb designation
      Line 1 0811KL
      line 2 1084
      pin1 2.08V
      pin2 3.34V
      pin3 5.04V

      U21 pcb designation
      Line 1 K333
      line 2 G117
      pin 1 .4mv
      pin 2 1.25V
      pin 3 2.51V

      U45 pcb designation
      line 1 AZ7805T
      line 2 807J48
      pin 1 3.9mv
      pin 2 .2mv
      pin 3 1.7mv

      U16 pcb designation
      line 1 AZ7805T
      line 2 807J48
      pin 1 4.2mv
      pin 2 0V
      pin 3 0V

      Comment

        #4
        Re: Vizio SV47OXVT1A Will n0ot power on

        Originally posted by shorteddiode View Post
        I found 6 regulators am I missing one.
        I circled 8 in red. There may be more, but with the angle of your photo, I can't tell.

        You only reported 5 test results.

        All 5 fuses test good with a continuity tester
        Early on, I tested fuses with the continuity tester. A fuse tested "good" because my multimeter beeped. Later on, I realized that my multimeter beeped for anything less than 75 ohms. As it turned out, my fuse was 18 ohms and was bad.

        A good fuse should measure less than 1.0 ohms. This is how I test it and recommend everyone else tests it. The continuity feature has its uses, but not when it comes to checking a fuse. I have kept that 18 ohm fuse as a reminder to myself.

        There is one Mastech multimeter that will beep "continuous" for anything less than 1800 ohms (eighteen hundred).
        Attached Files
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        Please do not post inline and offsite as they slow down the loading of pages.

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        Comment

          #5
          Re: Vizio SV47OXVT1A Will n0ot power on

          I'll try and get you a better photo in the am. I'll check the others you marked and list them at the same time.
          I forgot to list U19
          Line 1 0811KL
          line 2 1084
          pin 1 1.27
          pin 2 2.52
          pin 3 5.06
          Thanks for the help

          Comment

            #6
            Re: Vizio SV47OXVT1A Will n0ot power on

            OK finally made it out to the garage, here are the voltages for the other two voltage regulators
            U17 pcb designation
            line 1 K333
            line 2 G1117
            pin 1 2.07
            pin 2 3.31
            pin 3 5.01

            U22 pcb designation
            line 1 K333
            line 2 G1117
            pin 1 2.07
            pin 2 3.31
            pin 3 5.08

            Tested all 5 fuses on the AV board for voltage from left to right
            F6 5.08 F4 4.98 F1 5.08 F2 0 F5 5.08



            I also tested the following
            D120 pcb designation Shottky Diodes all out of circuit
            line 1 STPS2045CT
            line 2 GK10L
            line 3 CHN325
            Tested it out of circuit and it tested good

            D907 pcb designation
            line 1 STPS20L60CT
            line 2 GK08PVW
            line 3 CHN825
            Tested out of circuit and tested good

            D200 pcb designation
            line 1 STPS2045CT
            line 2 GK1OL
            line 3 CHN325
            Tested out of circuit and it tested good

            D240B pcb designation
            line 1 CQ825
            line 2 B20H100G
            Tested out of circuit and tested good

            D240A pcb designation
            line 1 CQ825
            line 2 B20h100G
            Tested out of circuit and tested good.

            Q905 pcb designation
            line 1 FQPE
            line 2 3N80C
            Mossfet I beleive it is leaky, when tested with black lead on drain and red lead on source and touching G&D together. Using an analog meter the needle would go to about center, hold for about 1 sec then fade to 0.

            Tested the following transistors in ciruit with a BK 520B they all tested good

            Q651 pcb designation
            line 1 K3569

            Q652 pcb designation
            line 1 K3569

            Q601 pcb designation
            line 1 K3568

            Q602 pcb designation
            line 1 K3568

            Let me know if you need anything else

            Comment

              #7
              Re: Vizio SV47OXVT1A Will n0ot power on

              I forgot to add that I also tested all the electrolytic caps on the power supply. I tested in circuit with a blue esr meter and they all seem to be with in specs.

              Comment

                #8
                Re: Vizio SV47OXVT1A Will n0ot power on

                Originally posted by shorteddiode View Post
                I have no voltage out of the power supply except for the 5.5Vdc at the stand by. I checked voltages regulators on the AV main board with the following results
                Observations so far.

                1) So U16 and U45 are both 7805 regulators and both have on input voltage on the main board.

                2) I have no idea where they are on the board because I can't read the pcb designations. Thus, the two above could be working properly since they could be for a USB port or something similar. Or they could be responsible for the sound and dying?

                3) 5.5V standby seems high to me. In your picture with the power board connectors, it not so clearly says 5VSB. At 5.5V SB, it is running 10% out of spec.

                4) Somewhere on the power board connector should be a pin marked PS_ON. This is generated by the main board to tell the power supply to power on the secondary voltages. PS_ON is enabled when voltage is typically > 3V.

                5) So what is PS_ON when you press the on/off button?
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                Please do not post inline and offsite as they slow down the loading of pages.

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                Comment

                  #9
                  Re: Vizio SV47OXVT1A Will n0ot power on

                  U45 and U16 are the two to the far right on the AV board.
                  Do you think the mosfet on the power supply is OK.
                  I added the info below. I'll check the PS_ON in the am

                  Q905 pcb designation
                  line 1 FQPE
                  line 2 3N80C
                  Mossfet I beleive it is leaky, when tested with black lead on drain and red lead on source and touching G&D together. Using an analog meter the needle would go to about center, hold for about 1 sec then fade to 0.

                  Comment

                    #10
                    Re: Vizio SV47OXVT1A Will n0ot power on

                    Originally posted by shorteddiode View Post
                    Q905 pcb designation
                    line 1 FQPE
                    line 2 3N80C
                    Mossfet I beleive it is leaky, when tested with black lead on drain and red lead on source and touching G&D together. Using an analog meter the needle would go to about center, hold for about 1 sec then fade to 0.
                    I don't have an analog multimeter at home so I can't comment on how it is supposed to behave. For mosfets, I do a simple test for shorts.
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                    Comment

                      #11
                      Re: Vizio SV47OXVT1A Will n0ot power on

                      Standby is 5.13, PS_ON has 0 volts at all times. The black wire for the PS_ON correlates to the fuse that has no power also. How do you check a mosfet for shorts?

                      Comment

                        #12
                        Re: Vizio SV47OXVT1A Will n0ot power on

                        where does the PS_ON power originate from, the main board? Does anyone have a troubleshooting guide for this TV. Are there any good troubleshooting books for LCD/Plasma TV's

                        Comment

                          #13
                          Re: Vizio SV47OXVT1A Will n0ot power on

                          Originally posted by shorteddiode View Post
                          Standby is 5.13, PS_ON has 0 volts at all times. The black wire for the PS_ON correlates to the fuse that has no power also. How do you check a mosfet for shorts?
                          1) PS_ON at 0V means the main board isn't generating it. You might want to check the on/off switch panel to make sure there is voltage present?

                          2) See section on mosfets.

                          https://www.badcaps.net/forum/showpo...4&postcount=19

                          3) Please circle in your diagram which black wire and fuse. Post a close up picture of that area.
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                          If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                          We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                          Please do not post inline and offsite as they slow down the loading of pages.

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                          Comment

                            #14
                            Re: Vizio SV47OXVT1A Will n0ot power on

                            Here is the simple explanation how LCD TV works.
                            Attached Files
                            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

                              #15
                              Re: Vizio SV47OXVT1A Will n0ot power on

                              Thanks, retiredcaps and budm

                              Comment

                                #16
                                Re: Vizio SV47OXVT1A Will n0ot power on

                                The red pencil is pointing to the fuse that has no power to it. the black wire on the far right goes to the PS_ON pin on the power supply board. Do I have a bad main board?
                                Attached Files

                                Comment

                                  #17
                                  Re: Vizio SV47OXVT1A Will n0ot power on

                                  Can you retest fuse F2 with just ohms and not continuity?
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                                  If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                                  We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                                  Please do not post inline and offsite as they slow down the loading of pages.

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                                  Comment

                                    #18
                                    Re: Vizio SV47OXVT1A Will n0ot power on

                                    The fuse shows 0.7 ohms, and just for giggles I checked the black wire and it is 0.7 ohms also

                                    Comment

                                      #19
                                      Re: Vizio SV47OXVT1A Will n0ot power on

                                      Am I right in thinking I need to repalce the main board? I found one for about $80.00 but hate to spend the money if I don't have too.

                                      Comment

                                        #20
                                        Re: Vizio SV47OXVT1A Will n0ot power on

                                        One thing you can try is to feed the PS_ON pin on the main board using 1K resistor from 5VSTBY pin to the PS_ON pin, but you MUST cut or remove PS_ON wire that goes back to the main board due to the transistor that supplies the PS_ON signal on the main board may be stuck on at this moment. If the power supply does kick on and you can see that the TV will function normal, then the problem can be just bad PS_ON signal from the CPU.
                                        See this link: https://www.badcaps.net/forum/showthread.php?t=22309
                                        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

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