Vizio sv420m black screen

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  • trixter
    Member
    • Mar 2011
    • 13

    #1

    Vizio sv420m black screen

    All I get is a black screen when plugged in and power on. Power board is DPS-260JP. Board doesn't seem to have any burnt parts or bulging caps. Something I noticed was that when I wiggle the wider plug around, the back light would flash for split seconds. I would slowly move the plug around stop as soon as the back light comes on. The back light would then stay on. I notice this blue LED lights up for couple seconds then it fades away and the back light turns off. Any suggestions.
  • dumpystig
    Badcaps Veteran
    • Jul 2011
    • 485
    • UK

    #2
    Re: Vizio sv420m black screen

    Once you get the b/l on does it then stay on and the TV runs fine?
    System: HP xw6600 Workstation, 650W PSU | 2x Intel Xeon Quad E5440 @2.83GHz | 8x 1GB FB-DDR2 @ 667MHz | Kingston/Intel X25-M 160GB SSD | 2x 1TB Spinpoint F3, RAID0 | 1x 1TB Spinpoint F3, backup | ATI FireGL V7700 512MB | Sony Optiarc DVD +/-RW | Win 7 Ultimate x64 | 2x Dell UltraSharp U2410f | Dell E248WFP

    Comment

    • trixter
      Member
      • Mar 2011
      • 13

      #3
      Re: Vizio sv420m black screen

      No. Once I get b/l to stay on, I see a blue LED on the board that is lit up. It will light up for like 5 sec and then fade away. After it fades off, the b/l goes out.

      Comment

      • Dgtech
        E. Technician
        • Apr 2009
        • 1462
        • Steeler

        #4
        Re: Vizio sv420m black screen

        was there ever a fix found for this issue?
        The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

        Comment

        • ac4aq
          New Member
          • Dec 2010
          • 5

          #5
          Re: Vizio sv420m black screen

          I sure sounds like soldering, plug/cable or other intermittent connection issues were the trouble here.

          Comment

          • JHOFFMAN
            Professional
            • Dec 2011
            • 9
            • USA

            #6
            Re: Vizio sv420m black screen

            If you have sound then problem is usually the backlight inverter, replace.

            Comment

            • Dgtech
              E. Technician
              • Apr 2009
              • 1462
              • Steeler

              #7
              Re: Vizio sv420m black screen

              I asked before about this set beacause there was one on CL that I was negotiating on. I finally picked it up today.

              Here is the issue:

              Not turning on at all. - Sounds easy enough

              Front Vizio symbol is amber and does not change with power button.

              Caps are visually ok and no burnt components on the board. I see a smaller red rectangular fuse on the power board. I have to take the board out to check this one but for now here is the rest of my checks.

              117VAC across main fuse - OK
              5VSB from power board to mainboard - OK
              Two fuses on mainboard checked - OK
              PS-on = 0.017 VDC before, during, and after power button is pressed.

              It's been a while for me, it's gonna be fun getting back into this.
              The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #8
                Re: Vizio sv420m black screen

                Has it got the infamous U33?
                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

                • Dgtech
                  E. Technician
                  • Apr 2009
                  • 1462
                  • Steeler

                  #9
                  Re: Vizio sv420m black screen

                  It's layout is different than the usual vizio vw42L or vo42L. The power board holds the inverter and there is a mainboard and Tconn. It has some LDO regs on it. Two have 5v inputs and 3.3vdc on one, 3v on the other. There is a third one that doesnt have any voltage to it. I'm thinking that this one needs power from once it's turned on.

                  I have to take some pictures right now and I'll post it.
                  The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                  Comment

                  • Dgtech
                    E. Technician
                    • Apr 2009
                    • 1462
                    • Steeler

                    #10
                    Re: Vizio sv420m black screen

                    I took some readings off of the regulators.

                    U2 = 3.3 out - 5 in
                    U3 = 3.26 out - 5 in
                    U4 = 1.25 out - 3.3 in
                    U5 = 3.3 out - 5 in
                    U6 = 0 out - 0 in
                    U7 = 3.3 out - 5 in


                    If remembering correctly, that ps-on should have something right? Not zero volts.
                    Attached Files
                    The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                    Comment

                    • retiredcaps
                      Badcaps Legend
                      • Apr 2010
                      • 9271

                      #11
                      Re: Vizio sv420m black screen

                      Originally posted by Dgtech
                      117VAC across main fuse - OK
                      I find it a lot safer if you just do a simple resistance test on the main fuse versus measuring up to 120V AC (or 240V AC in other countries). Both achieve the same result.
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                      Comment

                      • retiredcaps
                        Badcaps Legend
                        • Apr 2010
                        • 9271

                        #12
                        Re: Vizio sv420m black screen

                        Originally posted by Dgtech
                        U6 = 0 out - 0 in

                        If remembering correctly, that ps-on should have something right? Not zero volts.
                        Something is obviously wrong with U6. U6 looks like an adjustable regulator (as shown in picture). That means the outpin pin should be adj + 1.25V. In this case, if adj pin is 0.0V, then output should be 0.0 + 1.25 or 1.25V.

                        PS_ON is generated by the main board to tell the power supply to turn "on". It is usually 3V or higher.

                        PS. I can't believe how many Vizios are failing because of bad voltage regulators.
                        Last edited by retiredcaps; 07-06-2012, 02:54 PM. Reason: typo, grammar
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                        • retiredcaps
                          Badcaps Legend
                          • Apr 2010
                          • 9271

                          #13
                          Re: Vizio sv420m black screen

                          Originally posted by Dgtech
                          I took some readings off of the regulators.

                          U2 = 3.3 out - 5 in
                          U3 = 3.26 out - 5 in
                          U4 = 1.25 out - 3.3 in
                          U5 = 3.3 out - 5 in
                          U6 = 0 out - 0 in
                          U7 = 3.3 out - 5 in
                          1) BTW, when I post instructions for people, I always ask for the measurement of all 3 pins and the part numbers. Getting the measurements of all the pins is important if it is an adjustable voltage regulator. Getting the part number is important so we know what the expected output voltage should be.

                          For example,

                          U100
                          AS1117-33
                          pin 1 = 0.0
                          pin 2 = 3.3
                          pin 3 = 5.0

                          2) After looking at your results again, U3 is suspect too. If it is a fixed 3.3V output regulator, it is barely within spec assuming a +/- 1%.

                          3.3 x 0.99 = 3.267V
                          3.3 x 1.01 = 3.333V

                          3) If U3 is an ajustable regulator and the adj pin is 2.00V, then 2.00 + 1.25 = 3.25V.
                          Last edited by retiredcaps; 07-06-2012, 02:53 PM.
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                          Comment

                          • tom66
                            EVs Rule
                            • Apr 2011
                            • 32560
                            • UK

                            #14
                            Re: Vizio sv420m black screen

                            Also, a very slightly low reading is sometimes indicative of an oscillating regulator. If you have a scope, check the Vout pin.
                            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

                            • Dgtech
                              E. Technician
                              • Apr 2009
                              • 1462
                              • Steeler

                              #15
                              Re: Vizio sv420m black screen

                              Any chance of a service manual??
                              The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Vizio sv420m black screen

                                Service manuals, Vizio will never give out complete info.
                                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

                                • Dgtech
                                  E. Technician
                                  • Apr 2009
                                  • 1462
                                  • Steeler

                                  #17
                                  Re: Vizio sv420m black screen

                                  Here are more of the readings:

                                  U2 (1117) IN 5.2 OUT 3.3 ADJ 2.07
                                  U4 (1117) IN 3.26 OUT 1.25 ADJ 0
                                  U6 (1117) IN 0 OUT 0 ADJ 0
                                  U7 (1117) IN 5.18 OUT 3.25 ADJ 2.01

                                  U3 and U5 are a different type of regulators marked (L471 G1084)

                                  U3 = IN 3.16 OUT 1.24 GND
                                  U5 = IN 3.14 OUT 1.25 GND

                                  5VSB = 5.22 from power board
                                  12V = 0 from power board

                                  I'm thinking that the 12V isnt present until the unit is on - out of standby.
                                  I dont know if that is the same thing with U6's voltages.

                                  I'm just not sure.
                                  The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                                  Comment

                                  • Dgtech
                                    E. Technician
                                    • Apr 2009
                                    • 1462
                                    • Steeler

                                    #18
                                    Re: Vizio sv420m black screen

                                    On the service manual troubleshooting flow chart, they say to check pin 2 of U6 for 8VDC however the 12V to this board is not active until the unit comes out of standby. Then, I'd think, the 12V gets regulated down to 8V.
                                    The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                                    Comment

                                    • Dgtech
                                      E. Technician
                                      • Apr 2009
                                      • 1462
                                      • Steeler

                                      #19
                                      Re: Vizio sv420m black screen

                                      I'm thinking about pulling U6 for the hell of it, just to see what will be on the input pad when it's off the board. If there is no input voltage, U6 is not to blame - not yet at least. If U6 is shorted and grounding out it's input voltage then there should be the correct input voltage there on the input pin. That is... again....if this voltage is supposed to be present in standby.
                                      The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                                      Comment

                                      • retiredcaps
                                        Badcaps Legend
                                        • Apr 2010
                                        • 9271

                                        #20
                                        Re: Vizio sv420m black screen

                                        Originally posted by Dgtech
                                        I'm thinking about pulling U6 for the hell of it, just to see what will be on the input pad when it's off the board.
                                        No need to desolder U6, just test for shorts on all 3 pin combinations in circuit.

                                        Does 12V come up if the power board is disconnected from the main board?
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