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Vizio VW37 Power Supply PSON working but no 12v or 24v output

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    #21
    Service Manual

    I have attached the service manual for the vizio VW37L. I am pretty sure that U2,U8, and U33 should have a Vin of 5v, and a Vout of 3.3v.
    Attached Files

    Comment

      #22
      Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

      OK will do,

      Hope this is of some help to others
      Additionally have several dozen more manuals

      Regards
      KJINTF

      PS - Check out the differences between the two posted manuals - One is missing several chapters, skips from section 3 > 9
      Attached Files
      Last edited by KJINTF; 12-19-2011, 08:29 AM. Reason: Saw above post - check the difference between the two manuals

      Comment

        #23
        Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

        Probably completely irrelevant as I dont understand half of what has been posted in this thread and I am well out of my depth but 3 bits have struck me as being possibly connected:

        "so I jumped on e-bay and ordered some new caps for a few bucks."


        "However, your symptom is completely dead rails - almost always, with bad capacitors, you will get some voltage on those rails, but it will be too low"

        " I turned on the TV and saw that the voltage instantly jumped to around 24 before quickly fading to around 1.546v where it remained steady. The 12v rails also instantly jumped to around 12v and then quickly faded to 1.09v where it remained steady. "


        Have you tested/replaced any other caps that relate to the PSON
        voltage with ebay caps.


        Were the caps you got off ebay good? - Rubycon/Panasonic or general purpose
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

        Comment

          #24
          Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

          Originally posted by selldoor View Post
          Probably completely irrelevant as I dont understand half of what has been posted in this thread and I am well out of my depth but 3 bits have struck me as being possibly connected:

          "so I jumped on e-bay and ordered some new caps for a few bucks."


          "However, your symptom is completely dead rails - almost always, with bad capacitors, you will get some voltage on those rails, but it will be too low"

          " I turned on the TV and saw that the voltage instantly jumped to around 24 before quickly fading to around 1.546v where it remained steady. The 12v rails also instantly jumped to around 12v and then quickly faded to 1.09v where it remained steady. "

          Have you tested/replaced any other caps that relate to the PSON
          voltage with ebay caps.


          Were the caps you got off ebay good? - Rubycon/Panasonic or general purpose

          He replaced the caps on the power supply. They've pretty much traced the problem back to the main board so it likely doesn't have anything to do with the power supply or the replaced caps even though they needed replacing if they were bulged

          Comment

            #25
            Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

            Hi everyone,

            I have a VIZIO WX37L and two days ago it stopped working. The problem is very similar to Tetranitrate’s. When the TV is plugged in the VIZIO logo glows orange. Turning the TV on will result in the VIZIO logo turning white (however, no sound and no image). Two or three seconds later the VIZIO logo glows orange again. At first glance, I look the power board (Part#0500-0505-0420) for bad caps but all of them since to be OK.

            Tetranitrate: What is the status of your issue?

            Comment

              #26
              Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

              Originally posted by ekl10029 View Post
              Hi everyone,

              I have a VIZIO WX37L and two days ago it stopped working. The problem is very similar to Tetranitrate's. When the TV is plugged in the VIZIO logo glows orange. Turning the TV on will result in the VIZIO logo turning white (however, no sound and no image). Two or three seconds later the VIZIO logo glows orange again. At first glance, I look the power board (Part#0500-0505-0420) for bad caps but all of them since to be OK.

              Tetranitrate: What is the status of your issue?
              You would probably be better starting your own thread as whilst the problem may appear similar it may not be. You should also post pics of your own boards (using the manage attachments) as the experts may be able to spot problems you cant. There are other posts on this site and on the web suggesting U33 may be a problem see "Vizio VW37L - NO PICTURE, NO SOUND" You could also take the voltage measurements mentioned in both these threads and see how yours compare - maybe replacing U33, if it shows as faulty, would fix it for you.
              Please upload pictures using attachment function when ask for help on the repair
              http://www.badcaps.net/forum/showthread.php?t=39740

              Comment

                #27
                Updated voltage readings

                I started following the DC-DC converter troubleshooting flow chart (1st attachment) from the service manual. In the attached flow chart I have included my readings when they differ from the expected value. All the numbers given in red are with the power supply switched "on" and the Vizio logo illuminated white. The readings given in blue are when the main board is only being supplied with the standby 5v.

                This time I measured the correct voltages across all of the LDO's:

                Chip | Vin | Vout

                U2 | 5.142v | 3.31v

                U7 | 3.306v | 1.27v

                U8 | 5.142v | 3.333v

                U9 | 3.30v | 1.515v

                U33 | 5.10v | 3.30v

                I think they always had the correct voltage, and the first time around I was just measuring them wrong. I was using the ground pin as reference and for U2, U8, and U33 the ground pin is around 2.07v. I saw this mentioned in a separate badcaps thread, and so for these measurements I used the case as ground.

                While following the flowchart, the first problem I encountered (apart from the PSON rail being a bit low at 3.167v) was with the U1 chip. My voltage readings of U1 are labeled in the 2nd attachment, along with the values I measured for OPWRSB(R20) (I was not sure what they wanted me to measure at this resistor, so I measured both the voltage and resistance values). Pins 1 and 3 on U1 would remain around 5.1v regardless of whether the power supply was turned "on". Pins 2 and 4 would drop from about 5v down to about 0v when the power supply was turned on. U1 is labeled 4953GM, and is a power mosfet (3rd attachment is the pinout for this chip).

                I am not sure what the flowchart means when it says "Check U1 pin1&2 or pin3&4, should have -1V more.". But since none of my voltage readings on any of the pins 1-8 were 1V off from each other (in either direction, for a +V or -V) I suspect that this might be an indicator of a problem.

                R20 is 9.88kΩ and on one side (testing location shown in the image) has a voltage reading of 3.3v with the power supply off and a voltage reading of about 0v with the power supply on.

                Does anyone have any suggestions?
                Attached Files

                Comment

                  #28
                  Re: Updated voltage readings

                  Originally posted by Tetranitrate View Post
                  Pins 1 and 3 on U1 would remain around 5.1v regardless of whether the power supply was turned "on". Pins 2 and 4 would drop from about 5v down to about 0v when the power supply was turned on.
                  1) When measuring the voltage of U1, what did you use for ground?

                  2) For mosfets, I like to do a simple resistance test to make sure it is not shorted. I measure the resistance between S-G, S-D, and D-G. Since you have a "1" and "2", you will have 6 readings. That is, S1-G1, S1-D1, D1-G1, S2-G2, S2-D2, and D2-G2.

                  Any "in circuit" reading less than 30 ohms suggests it may be shorted.
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                  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.

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                  Comment

                    #29
                    Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                    What is the SMD marking on R20?
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                    Comment

                      #30
                      Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output
                      1. When measuring U1, the case was used for ground
                      2. All the mosfet readings looked good (well above 30Ω)
                        • D1G1: about .5MΩ
                        • D1S1: 10's of kΩ (was still fluctuating after 20s of probing, but in the multiple kΩ range
                    • S1G1: about 264.6kΩ
                  • D2G2: A few MΩ
                  • D2S2: 10's of kΩ
                  • S2G2: 263.2kΩ
                  • R20 is too small for markings, but according to the parts list (attached image) it should be 10kΩ, so my reading of 9.88kΩ seems to be within range.
                    • Attached Files

                    Comment

                      #31
                      Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                      All those mosfet readings, voltages and resistance, look correct to me. I have no idea what the -1V means though.
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                      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

                        #32
                        Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                        Originally posted by retiredcaps View Post
                        All those mosfet readings, voltages and resistance, look correct to me. I have no idea what the -1V means though.
                        It looks like it has been poorly translated, from reading it I understand it to mean U1 pins 5 6 7 and 8 should be +5V WRTG with the power switch on, while pins 1 & 2 and 3 & 4 (not measured to ground) should be +4V or thereabouts.

                        Could be totally wrong, but I think for sure something has gotten lost in the translation.

                        Jim
                        Last edited by bbjunkie; 12-31-2011, 05:27 AM.

                        Comment

                          #33
                          Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                          Could be totally wrong, but I think for sure something has gotten lost in the translation.
                          I feel like that is the case, but it seems like there could only be a couple of different correct original meanings.

                          I think your interpretation that:
                          pins 1 & 2 and 3 & 4 (not measured to ground) should be +4V or thereabouts.
                          is correct.

                          Although, even if the original intention was that it should be +6 volts or just that there should be a 1 volt difference between any of those pins - I am not getting either of those outputs. So I feel like no matter what way it is interpreted I am not getting the correct readings, and that it is an indicator of a problem. The MOSFET appears to be good (not burnt out), so I am guessing whatever is causing this issue occurs before the U1 chip.

                          Comment

                            #34
                            Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                            Although, now that I think about the overall formatting of the flow chart, I am not sure what to make of my values.

                            In each diamond box, they list a chip or jumper wire with some pins. In the rectangular box on the right they list what the value should be, and if it is not that - they have a numbered series of things to check.

                            For U1 pins 5,6,7, and 8 they say:

                            The voltage is about +5V while power switch on
                            which makes me think I should not even be worrying about the numbered checklist underneath, since my voltages on those pins is correctly going from .25V to 5.111V when the power is turned on.

                            This would mean that the first part of the flow chart where my measured values do not match up with the expected values is at U6.

                            U6 is labeled AP1513, and is a PWM control 2A step-down converter (datasheet attached). The flow chart says that the output on pins 5 and 6 should be about 1.6V, but I am only getting .026 volts.

                            I will look into this chip and the expected operation a bit more and report back with my findings, but if anyone knows what I should be looking for, I would greatly appreciate the help.
                            Attached Files

                            Comment

                              #35
                              Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                              Originally posted by Tetranitrate View Post
                              For U1 pins 5,6,7, and 8 they say:

                              The voltage is about +5V while power switch on

                              which makes me think I should not even be worrying about the numbered checklist underneath, since my voltages on those pins is correctly going from .25V to 5.111V when the power is turned on.
                              No, I disagree. They have said those pins should have that reading, they don't.

                              Ok, the correct diagnostic process would have been to check for +5v and move on, but by chance you have discovered the values on pins 1+2 and 3+4 are low. Just because you aren't meant to measure them doesn't mean if they are wrong it should be disregarded (in my opinion)

                              Have you checked U1 out of circuit? (it's just two MOSFETs in a SO-8 package)

                              Don't take this as criticism, i'm just giving you my thoughts on it.


                              Jim
                              Last edited by bbjunkie; 01-01-2012, 04:16 PM.

                              Comment

                                #36
                                Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                I'm curious.. what did you measure between pins 1 and 2 of U1 ? also between 3 and 4 ?

                                Comment

                                  #37
                                  Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                  I have not tested U1 out of circuit. I do not have the stuff to remove SMD devices yet, and was planning on ordering some quik-chip and any replacement components at the same time.

                                  Just measured voltages of U1:
                                  • Pin 1-2: 4.925V
                                  • Pin 3-4: 4.924V


                                  And no criticism taken
                                  This is the first time I am doing an electronics diagnostic that is this "in-depth" and really want to learn the proper methodology.

                                  Comment

                                    #38
                                    Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                    U6 pins 5 and 6 are supposed to be reading 1.6 volt, but the measured values are only reading .026 volts.

                                    I have attached a picture of the U6 section of the main board, along with a modified schematic which includes the silk-screened numbers that correspond to each component.

                                    U6 is a PWM control 2A Step Down Converter which should be outputting 1.6 volts. According to the datasheet, the input voltage needs to be 3.6 to 18 volts, and the output voltage can be .8 volts to Vcc. Since my Vcc input voltage on pin 4 is only 1.09v I figure that is why the output voltage is low. Unfortunately the flow chart only says to check F2 and U1 if the readings on U6 are incorrect. I already know that F2 is good, and U1 is sort of a mystery right now.

                                    According to this post, the values of pins 1,3,5,6,7, and 8 on U1 are 5 volts when the system is on, which matches up with my readings; however, the flowchart line
                                    "Check U1 pin1&2 or pin3&4, should have -1V more."
                                    is somewhat unclear.

                                    Since F2 and U1 are the first two things it says to check if the U6 values are off, these two issues are probably related, but I am at a loss of what to check for now.
                                    Attached Files

                                    Comment

                                      #39
                                      Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                      Did you have U6 off the board? It doesnt look like the soldering is great on it. If you didn't, sure might be worth trying to tidy those connections up a bit. Perhaps your friend had someone look at it ?

                                      Comment

                                        #40
                                        Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                        Originally posted by Tetranitrate View Post
                                        U6 pins 5 and 6 are supposed to be reading 1.6 volt, but the measured values are only reading .026 volts.

                                        I have attached a picture of the U6 section of the main board, along with a modified schematic which includes the silk-screened numbers that correspond to each component.

                                        U6 is a PWM control 2A Step Down Converter which should be outputting 1.6 volts. According to the datasheet, the input voltage needs to be 3.6 to 18 volts, and the output voltage can be .8 volts to Vcc. Since my Vcc input voltage on pin 4 is only 1.09v I figure that is why the output voltage is low. Unfortunately the flow chart only says to check F2 and U1 if the readings on U6 are incorrect. I already know that F2 is good, and U1 is sort of a mystery right now.

                                        According to this post, the values of pins 1,3,5,6,7, and 8 on U1 are 5 volts when the system is on, which matches up with my readings; however, the flowchart line is somewhat unclear.

                                        Since F2 and U1 are the first two things it says to check if the U6 values are off, these two issues are probably related, but I am at a loss of what to check for now.
                                        Check diode D4 for short circuit using the diode test mode on your meter. Test both ways, should conduct one way at ~200-500mV, and none the other way.
                                        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

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