Announcement

Collapse
No announcement yet.

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

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

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

    Hi everyone,

    I am currently in the process of diagnosing and (hopefully) repairing my 37 in Vizio, and could really use some help.

    Background:

    My friend's Vizio VW37 recently broke (I think it is a few years old), and he told me I could have it. I had already fixed one LCD before (my sisters Samsung, with obviously bad bloated capacitors on the power supply), and was/am feeling confident that I can fix this issue without needing to buy new boards (i.e. a fix done by replacing individual caps/chips instead of just the entire board). I like to think my skill level is decent: I am finishing up my undergrad EE career and plan on getting my masters, I have a well stocked workspace (Weller soldering iron, a shiny new Fluke 115 I just got for my birthday, third hands, hemostats, etc), and I have been soldering and de-soldering various electronics for close to 10 years.

    The Problem:

    When the TV is plugged in the Vizio logo glows orange. An attempt to turn the TV on (using either the power button or the remote - both "work") will result in a few second delay before the Vizio logo turns white but nothing else happens (no sound, image, etc). A bright light was held up to the screen to see if the pixels were actually changing, in case it was strictly a bad back-light , but no pixels were seen to change. The logo remains white and the TV can be "shut off " normally using the remote or the power button.

    My Diagnostics and Fix Attempt:

    The first thing I did after I took the back of the TV off was to look for obviously bloated/damaged capacitors, but none were readily apparent. I then used my multimeter to test the voltages the power supply board was giving off. The connector to the main board was correctly giving off 5v at 3 of the pins, but the 12v pins were reading 0v. The 24v pins going to the inverter board were also giving off 0v.

    I de-soldered a large heat-sink for the the power transistors on the secondary side of the power board in order to get a better look at the capacitors underneath it. The capacitors feeding the 12v and 24v pins were bulging very slightly (it seemed, now I think it was probably just in my imagination).

    Pics:


    Above: The two slightly bloated 36v 680 micro-farad capacitors feeding the 24v pins going to the inverter board (the two 16v caps feeding the 12v pins were in the process of being replaced when this photo was taken).


    Above: A closeup of the slightly bloated 36v caps (the two new 16v caps can be seen in the background)

    "Great" I thought - this plus the incorrect voltage readings made me think I had found the problem, so I jumped on e-bay and ordered some new caps for a few bucks. When the 16v 1500 micro-farad caps that feed the 12v pins arrived, I de-soldered the old ones and put in the new ones (which can be seen in the second photograph just above the caps with the red arrows). I plugged in the power cord and tested the voltage off the 12v pins, damn - still 0v.

    To the INTERNET!

    My searching brought me to a few various forums. I read through many of them, including the problems and fixes from this badcaps post:
    https://www.badcaps.net/forum/showthread.php?t=13615
    along with the numerous other links that thread went to, and the fix attempts on those threads. There was a lot of good info, and I learned much about how a SMPS works, but still nothing that was able to fix my particular problem.

    After reading through a number of different threads, I felt like I was closing in on the problem. One thing I read, which I briefly thought may be the problem, was that the power board needed to be connected to the main board, and receive a Power Supply On (PSON) signal before it output anything on the higher voltage pins.

    ::

    I was testing the voltage on the pins while the board was still sitting on my desk disconnected from everything but the mains. I quickly realized why having a PSON made perfect sense. When the TV is in standby mode, it does not require electricity - except for the 5v to the main board to power the IR receiver and various components that will tell the TV when to fully power on. There is no need to have 24v going to the inverter, or 12v going to the main board (which I am guessing powers the speakers).

    I screwed the power supply board back into the metal frame, and made all the necessary wire connections, and connected my multimeter to one of the 12v pins. I then powered up the TV with the remote, waited for the logo to turn white, and then checked the voltage - still 0v. The PSON pin did jump from .014v to 3.166v when the TV was "turned on", so at least the mainboard was correctly responding to the power-on input signal from the remote.

    I have also checked all the diodes I could identify, and they all seem to be in working order. There is no voltage at the output of either the 12v or 24v power transistors (or the transformer) on the low voltage side of the board (tested with the PSON pin being off and HIGH at 3.166v, so I guess I wasted a few bucks on electrolytic capacitors - no great loss).

    Here are some shots of the front and back of the power supply with labels added:

    Front:


    Back:


    There seemed to be heat "damage" to the mechanical solder connection that held on the heatsink that was attached to IC901. It looked like this chip got the heatsink hot enough to melt the solder. A picture of this is shown below:


    The ceramic capacitor that is next to this heatsink is also chipped on the top, shown below:


    There were other signs of solder being reheated. Shown below is a solder joint for a jumper wire. This jumper wire connects the source of the 20N60C3 power transistor to a group of 4 resistors wired in parallel (R825 A,B,C, and D).



    One other spot where it looked like the solder had gotten hot was at the SCK 2512 Thermistor, shown in the picture below. The joint which had gotten hot was connected directly the neutral line of the power cord.



    One other small portion that looked like it may have been heat damaged was a diode that is located on the HV side very close to the opto-couplers. A picture of this is shown below.




    I am not sure if these photos of apparent heating, are actually damage or just results of normal board use, or possibly results of overheating without the components actually being damaged.

    I decided to attack the problem from the HV side for a bit. The large 450v 150micro-farad capacitor that filters the output from the full-wave input rectifier was measuring 169.7-170 volts, so everything was good up until that point.

    One interesting thing I noticed was that all the heat-sinks on the high voltage side were reading -62.6 VDC when compared to the mains/chassis ground. I measured the high voltage side of two of the opto-couplers, and this -62.6 VDC also appeared.

    So this is where I am at now. If anyone has any advice, it would be greatly appreciated.

    TL;DR
    Power supply not turning on the 12v & 24v outputs, even though a PSON signal of 3.166 is being sent to the HV side.

    #2
    Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

    Wow, this has to be one of the best threads yet. Excellent photos and debugging work so far.

    The design of this power supply looks to be two part. One 5V standby section which is working properly, and a 12V/24V "run" supply which provides power to the inverters, audio and other parts of the main board.

    There are a few things that could cause this problem:
    - Bad diodes on 12V/24V (but you ruled these out)
    - Bad Vcc supply for the 12V/24V switcher (seems likely)

    The Vcc supply can go bad for a number of reasons:
    - Failed cap for Vcc (looks like design uses a ceramic cap, so unlikely to be the fault.)
    - Open charging resistor
    - Failed controller IC (L6598)

    This is going to take some careful probing. Set up the board such that it is trying to turn on the rails. You'll need to have it upside down. Then probe pin 12 of the controller IC (relative to HOT ground - the negative terminal of the main bulk capacitor usually.) We are looking for about 10V for this IC.

    If you can't do this because of the design or otherwise - post first before trying. It may be instead possible to turn on the power supply using a 1k resistor if you have one.

    The pictures of the capacitors you posted are good; the capacitors are fine. The large canned capacitors even new out of the factory always seem to have an ever so slight bulge. Failed caps often have quite a significant bulge, at least several mm. It's important to note that caps do not have to bulge to be failed. 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, or have too much ripple or switch on and off repeatedly over a period of seconds as it destabilises the control loop of the SMPS.
    Last edited by tom66; 12-15-2011, 06:19 PM.
    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


      #3
      Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

      Originally posted by tom66 View Post
      Wow, this has to be one of the best threads yet. Excellent photos and debugging work so far.
      Agreed, great work on debugging and providing info. In the future, for members sake (especially mine), we prefer pictures posted using the manage attachments function so they are hosted here and not posted inline (for a number of reasons).

      Otherwise, good job and tom66 has excellent suggestions to try.

      That teal Rubycon 47uF cap might the startup cap. It should have steady DC voltage around 10 V.
      Last edited by retiredcaps; 12-15-2011, 06:20 PM.
      --- begin sig file ---

      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.

      --- end sig file ---

      Comment


        #4
        Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

        Originally posted by retiredcaps View Post
        That teal Rubycon 47uF cap might the startup cap. It should have steady DC voltage around 10 V.
        I noticed that too. But it looks to be in the wrong place for the startup cap. The SMPS IC is at the top of the board, but this is in the middle. Given its location, I'd say it's probably for the standby supply. Still, it would be good to check it. Looks like the TOPswitch or similar standby controller (likely the mystery chip) has a big heatsink on it, so that area probably gets hot.

        Overall, this is a very good design for a Vizio, but the power supply model code gives it away: DPS-247AP is a power supply made by Delta Electronics, who make very high quality power supplies, among other products. It looks like it might be a standard power supply they make and sell. This power supply is available for around $50 on eBay - but I'd suggest trying to repair it first as it would make a good learning experience!
        Last edited by tom66; 12-15-2011, 06:28 PM.
        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


          #5
          Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

          There are a couple of tests to try. One technique is to use a pair of AA batteries to raise PS_ON to 3 volts. Another is to use a 3.3K resistor from PS_ON to 5V Standby to do the same thing.

          Check the voltage across the large cap. This power supply has a PFC front end that is turned on only when PS_ON goes high. If the voltage across the large cap is 1.4 x the AC line voltage, the PFC is not turned onn. If it is close to 400 volts, PFC is on.

          If PFC never turns on, the problem is in the PS_ON path. If it turns on, it's in the main SMPS controller area.

          PlainBill
          For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

          Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

          Comment


            #6
            New Measurements

            Overall Update:

            When I was taking the new measurements that were suggested in the replies, I tested the 24v rails while 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. My statement in the first post that said both were reading an absolute 0v was inaccurate (I must have accidentally slid the decimal over in my head, and figured .1546v was close enough to 0v to just report it as 0v), sorry about that; however, this is the first time I am seeing that there is an initial jump to the correct voltage. I am putting this update first because it seems like a significant development.


            To tom66's suggestion:


            I set up the power supply so I could have access to the pins of the SMPS Controller, while the supply was fully plugged in and running. This was not as easy as it sounded at first.

            The HOT ground was connected to the various heat-sinks on the high voltage side of the board (this is the first time I have encountered this term "HOT ground", but from what I read - it is a separate ground used as the common on the HV side of the board, with the purpose of further isolating the primary side from everything else. Is this correct?).

            The hot-grounded heat-sinks read -62v with respect to the mains/chassis ground. I figured I could not just flip the board over and let the heat-sinks rest directly on the main metal frame of the TV, and the various wires connected to the supply were not long enough to allow me to have the power board resting elsewhere. In order to overcome this I cut up a cardboard box, and had the PSU resting upside-down on it, isolated from the main chassis. I noticed that the cold ground of the PSU connected to the chassis via some exposed solder lines around the screw holes. I put alligator clips around these screw holes, and wired them to the main chassis. I then tested the continuity (or dis-continuity) of everything to make sure everything was wired correctly. This entire setup is shown in the first attached image below.


            On a side note, this is the first time I am ever attempting a fix that is this in-depth, so if anyone has any comments about my techniques, any suggestions would be greatly appreciated. It is one of the reasons why I am trying to be so comprehensive in my descriptions (so if connecting the screw holes to the chassis with alligator clips is overkill, or if some old industry pro has always used discarded cereal boxes to isolate boards, etc, I would love to hear it).

            Anyway, once I was sure everything correctly wired I plugged it in, turned it on, and verified the voltage of the PSON pin was 3.166v. One thing to note (that I forgot to mention in the first post) is that the chip we are referring to as the SMPS controller, is labeled DLA001D. I am assuming that it is L6598 from PlainBill's post #11 in this thread.

            There is no obvious notch on the chip, so the datasheet's pin-out diagram was not much help, but it didn't make much of a difference since "both" pin 12s were reading 0vDC compared to the HOT ground. A picture of this is shown in the second attached image below.

            To retiredcap's suggestion:

            I've crossed the Rubycon. It reads 22.12v with a HIGH PSON, and 18.43v with a LOW PSON. The specs for that cap (which I missed in my initial diagram) are 50v 47uF.

            To PlainBill's suggestion:

            The PSON pin is correctly jumping to 3.166v when I turn the power on using the remote or the side button panel, so externally applying 3v should be unnecessary, right?

            The large 450v 150uF capacitor will instantly jump to 396.6v when the PSON goes high, but then quickly drops back down to the regular mains peak of 170v.

            Thoughts:

            Now that I am seeing that the 12v and 24v rails are correctly (albeit briefly) jumping to proper voltage, and that the power factor correction is briefly turning on (as shown by the mains filter cap temporarily jumping to 396v), am I right in thinking this entire problem is a capacitor issue? Are there any other types of problems that would allow everything to work for a fraction of a second before shutting down?
            Attached Files

            Comment


              #7
              Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

              A couple of suggestions/comments.

              1) For the pin orientation (deciding which is pin 1), see which pin 10 (GND) has close to 0.0 ohms resistance with respect to hot ground (or negative leg of largest capacitor).

              2) I believe if you use the negative leg of the largest capacitor on the hot side for ground, you will no longer see the negative DC readings on the heatsink.
              Last edited by retiredcaps; 12-16-2011, 04:58 AM. Reason: edit: original #2 was dumb idea
              --- begin sig file ---

              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.

              --- end sig file ---

              Comment


                #8
                Re: New Measurements

                Originally posted by Tetranitrate View Post
                Thoughts:

                Now that I am seeing that the 12v and 24v rails are correctly (albeit briefly) jumping to proper voltage, and that the power factor correction is briefly turning on (as shown by the mains filter cap temporarily jumping to 396v), am I right in thinking this entire problem is a capacitor issue? Are there any other types of problems that would allow everything to work for a fraction of a second before shutting down?
                Almost all power supplies in TVs (and most other devices) are fully isolated. The primary reason for doing this is to create a safety barrier between the user of the TV (who might touch the USB port, connectors, or connect it to other equipment) from the mains side. So, because of this, there are two "0V" points. One which is isolated and usually the entire chassis of the TV is connected to this. The other is relative to the mains power connector but it is variable depending on how whether the AC is positive or negative, which is why you get a nasty shock if you touch the heatsinks.

                How long do the rails remain high? Seconds?

                The L6598 gets its power from a starting resistor. Pin #1 is the one I have highlighted (I'm inferring this from the circuit, as it wouldn't work the other way around.)

                Some checks have been highlighted in the image.

                The EN1/EN2 pins could be turning off the controller because of a protection circuit which is malfunctioning.

                The Vs pin should be charged by a high value resistor >470k, or powered off the PFC or standby controller's Vcc.
                Attached Files
                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


                  #9
                  Re: New Measurements

                  Originally posted by Tetranitrate View Post

                  To PlainBill's suggestion:

                  The PSON pin is correctly jumping to 3.166v when I turn the power on using the remote or the side button panel, so externally applying 3v should be unnecessary, right?

                  The large 450v 150uF capacitor will instantly jump to 396.6v when the PSON goes high, but then quickly drops back down to the regular mains peak of 170v.
                  The purpose of driving PS_ON high using a resistor or battery is to allow troubleshooting without the need of having the main board hooked up. It also allows you to switch the main supply on and off easily.

                  Your initial response to a low output voltage was correct. at a fraction of the rated voltage, the power supply is not working. The fact that it momentarily jumps to full voltage is significant. Since both PFC and SMPS turn on, then off, this is not a failure of either, it's a problem in the control signal path.

                  You are into a gray area here. 3.166 volts is theoretically a 'high', however I have seen at least one case (on a Philips TV) where the voltage was about that high, but the main supply wasn't turning on. Goose it with a few tenths of a volt and the supply turns on. Typically I expect to see the control voltage at very close to 3.3 volts.

                  The fault may be a capacitor, but I wouldn't ignore the possibility it is a resistor. The easiest way to troubleshoot may be to trace the PS_ON control signal through the opto-isolator and determine where it drops out.

                  One possibility, just to cover the bases. Most designs turn the main supply and the PFC correction on by a single control line. Some designs sense the current demand on the input, and switch the PFC on when the load increases.

                  PlainBill
                  For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                  Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                  Comment


                    #10
                    Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                    Ok, I am pretty psyched.

                    First I tried PlainBill's suggestion of independently driving the PSON channel high, because it is a hassle needing to be attached to the rest of the tv while doing the other testing. I tried bridging the PSON and 5v with a 3.3k resistor (first picture below - this only dropped the 5v by a couple tenths of a volt, so PSON was being run at about 4.9v), and I also tried the a pair of AA batteries in series between PSON and ground (the PSON was being run at 3.214v from the batteries).

                    When each of these voltages was applied to PSON, the rest of the power supply switched on and a steady 12v and 24v (3rd pic) appeared on their rails.

                    This should mean that, right now, the worst case scenario is I externally apply signal of >3.2 volts in order to switch the supply on (and have a working tv)?

                    So at a voltage of 3.214 the PSON pin functions perfectly, and at a voltage of 3.166 it does not? Was my whole problem really just an issue of .048v?!?

                    Since the PSON signal is supplied by the main board, I guess my problem stems from there, right?
                    Attached Files

                    Comment


                      #11
                      Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                      Originally posted by Tetranitrate View Post
                      Ok, I am pretty psyched.

                      First I tried PlainBill's suggestion of independently driving the PSON channel high, because it is a hassle needing to be attached to the rest of the tv while doing the other testing. I tried bridging the PSON and 5v with a 3.3k resistor (first picture below - this only dropped the 5v by a couple tenths of a volt, so PSON was being run at about 4.9v), and I also tried the a pair of AA batteries in series between PSON and ground (the PSON was being run at 3.214v from the batteries).

                      When each of these voltages was applied to PSON, the rest of the power supply switched on and a steady 12v and 24v (3rd pic) appeared on their rails.

                      This should mean that, right now, the worst case scenario is I externally apply signal of >3.2 volts in order to switch the supply on (and have a working tv)?

                      So at a voltage of 3.214 the PSON pin functions perfectly, and at a voltage of 3.166 it does not? Was my whole problem really just an issue of .048v?!?

                      Since the PSON signal is supplied by the main board, I guess my problem stems from there, right?
                      That is surprising. I'd look towards the main board. A common failure is U33, but I'm not sure if that would cause your problem. Do you have a scope? Maybe the 3.166V is noisy due to a bad LDO. Or maybe the TV is shutting it down.
                      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


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

                        With the TV "Powered up" I took measurements of the five (AMC1117) voltage regulator chips that I found on the main board (pictured below).

                        Chip | Vin | Vout

                        U2 | 3.050v | 1.248v

                        U7 | 3.278v | 1.250v

                        U8 | 3.060v | 1.246v

                        U9 | 3.305v | 1.514v

                        U33 | 3.046v | 1.242v

                        According to this forum post, my voltages are not what they should be. The Vin of U7 and U9 are (correctly?) around 3.3v, but according to that post U2, U8, and U33 should have a Vin around 5v.
                        Attached Files

                        Comment


                          #13
                          Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                          Originally posted by Tetranitrate View Post
                          With the TV "Powered up" I took measurements of the five (AMC1117) voltage regulator chips that I found on the main board (pictured below).

                          Chip | Vin | Vout

                          U2 | 3.050v | 1.248v

                          U7 | 3.278v | 1.250v

                          U8 | 3.060v | 1.246v

                          U9 | 3.305v | 1.514v

                          U33 | 3.046v | 1.242v

                          According to this forum post, my voltages are not what they should be. The Vin of U7 and U9 are (correctly?) around 3.3v, but according to that post U2, U8, and U33 should have a Vin around 5v.
                          The readings you are using for comparison may not be from an identical board, but this is easy to check. In the upper right corner of the picture is the connector for the cable from the power supply. Just below it are two fuses - F1 and F2. Using a mounting screw as ground, what are the voltages on each end of those fuses?

                          PlainBill
                          For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                          Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                          Comment


                            #14
                            Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                            Fuse 1 reads 1.091v and fuse 2 reads 5.169v, and both these fuses read their respective voltages on both sides (so the fuses are good).

                            Comment


                              #15
                              Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                              Looks to me like NTC1 has a cold solder joint and there are several others that look similar.
                              .
                              Mann-Made Global Warming.
                              - We should be more concerned about the Intellectual Climate.

                              -
                              Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.

                              - Dr Seuss
                              -
                              You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
                              -

                              Comment


                                #16
                                Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                Originally posted by Tetranitrate View Post
                                Fuse 1 reads 1.091v and fuse 2 reads 5.169v, and both these fuses read their respective voltages on both sides (so the fuses are good).
                                5.169 would indicate it is for a 5V line (probably 5V_SB). 1.091 would probably be for a higher voltage supply (12V?) that has not come up.

                                PlainBill
                                For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                                Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                                Comment


                                  #17
                                  Summary so far

                                  Summary of the problem so far:

                                  The standby 5v portion of the power supply is functioning correctly, and sending that voltage to the main controller board. The main controller board will respond to the remote / push-button, and send a signal of 3.166v to the PSON, but the main portion of the power supply will only turn on for a fraction of a second when PSON first goes high (I am thinking that the initial voltage pulse to PSON will be a bit higher than 3.166, this can be tested if needed). The main portion of the power supply will turn on for a fraction of a second, and correctly send out 12v and 24v. After a few seconds the 12v and 24v settle down to around 1v. (This is the voltage that is being sent across fuse 1)

                                  Independently setting the PSON to high with a pair of AA batteries will result in the main portion of the power supply turning on. This sends out a steady 12v and 24v to their rails, where they will remain constant as long as the PSON is being independently driven. A faint sound is heard from the speakers when the main board is correctly receiving the 12v.

                                  It would seem as though the PSON voltage supplied by the main board is not high enough to tell the power supply to turn on.

                                  Should my next step be to trace out the PSON pin on the main board, and find out where it should be getting its voltage from?

                                  Comment


                                    #18
                                    Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                    That is a good description of the usual sequence. I take it PSON stays at 3.166V?

                                    And to answer an earlier question, the problem could be on either the main board (output too low) or the power supply (input not sensitive enough.) This is frustrating because with a schematic it would be easy to troubleshoot.

                                    PlainBill
                                    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                                    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                                    Comment


                                      #19
                                      Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                      Tetranitrate

                                      Not sure if you have the factory service manual or not - if not PM me and I will send it your way. It's about 2 megs so should easily go through email. There are several dozen detalied block diagrams covering the issues you are experiencing.
                                      As others have stated U33 is a common failure - not sure if it is related to your failure but worth a check. I have had two of theses Vizio's both with U33 problems and a few bad caps but U33 was the primary cause. 1117 chips are cheap and might be worth it just to replace it one way or the other.

                                      Good luck with the repairs

                                      Comment


                                        #20
                                        Re: Vizio VW37 Power Supply PSON working but no 12v or 24v output

                                        Originally posted by KJINTF View Post
                                        It's about 2 megs so should easily
                                        You can also attach here (using manage attachments) for the rest of us.
                                        --- begin sig file ---

                                        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.

                                        --- end sig file ---

                                        Comment

                                        Working...
                                        X