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VIZIO XVT373SV Not powering on

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    #1

    VIZIO XVT373SV Not powering on

    I have a VIZIO xvt373SV LED TV. Last week, I turned on the sleep timer for 30 minutes. Well the TV powered off after about 15 minutes (well before the sleep timer) and now I am not able to power the TV on.

    I believe the TV still has power going to it, as the VIZIO logo still glows orange when plugged into the wall. Hitting the power button on the side does not power the TV on though.

    I am thinking this is the main circuit board, but I am not 100% sure. Has anyone else heard of this problem or no of any solutions?

    I strongly thank everyone in advance.
    Tags: None
    #2
    Re: VIZIO XVT373SV Not powering on

    Vizio made both a model XVT373SV as well as an SV370XVT. Brilliant labeling scheme on their part. Don't have any resources on an xvt373sv.

    Comment

      #3
      Re: VIZIO XVT373SV Not powering on

      I'd probably first check to see if the PSU was supplying power at all past the point of the standby light.

      May also check if the main board is sending a power-on signal to the PSU or not

      Might help narrow it down
      "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
      -David VanHorn

      Comment

        #4
        Re: VIZIO XVT373SV Not powering on

        Thanks guys. I will use a voltmeter to check to see if proper power is getting supplied.

        Comment

          #5
          Re: VIZIO XVT373SV Not powering on

          Well I looked at it, it seems that the standby light is wired from the Main board. so the PSU connects the mainboard, and the main board connects to the standby light.

          Not quite sure how to diagnose this. Obviously either PSU problem or Main board problem. any suggestions?

          Comment

            #6
            Re: VIZIO XVT373SV Not powering on

            Originally posted by UTbaseball36 View Post
            Well I looked at it, it seems that the standby light is wired from the Main board. so the PSU connects the mainboard, and the main board connects to the standby light.

            Not quite sure how to diagnose this. Obviously either PSU problem or Main board problem. any suggestions?
            I've been through this so many times I should bookmark one of the explanations. The power supply is actually two supplies in one. The standby supply is always on when the AC cord is plugged in. The main supply is turned on by the main board. The control line is usually labeled PS_ON or something like that, and is usually high (>3 volts) to turn the supply on.

            The routine is to identify the standby output of the power supply (SB5V is one possible label) and verify it is correct. Then check the PS_ON signal. If it does not change when the power button is pressed, the problem is the main board. If it changes, and the main power supply outputs come up to their nominal voltages, the problem is the main board. If one or more do not come up, the problem is either the power supply or the load (main board or inverter) connected to that output.

            Test, then report the results for further directions.

            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

              #7
              Re: VIZIO XVT373SV Not powering on

              Thank you very much for the explanation. I did the routine you explained and came out with these results: The 5.1vSB (Stand by power) will stay at 5.1v all the time. Any other voltages do nothing, just stay at 0. Even when the power button is pushed. So from your explanation, that means its the main board, correct?

              Thank you again

              Comment

                #8
                Re: VIZIO XVT373SV Not powering on

                No, only if the PS_ON signal also does nothing. If that signal is OK then it's probably the PSU is not coming of out standby.
                "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                -David VanHorn

                Comment

                  #9
                  Re: VIZIO XVT373SV Not powering on

                  Yeah, this is kind of ambiguous. Were you able to identify a PS_ON (or equivalent) pin? Did it always stay at the same voltage?

                  There are several different designs; I'd say that on 75% of TVs the PS_ON signal goes high to turn the TV on. On others it is labeled Standby and goes low when the TV is turned on.

                  PainBill
                  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 XVT373SV Not powering on

                    Originally posted by PlainBill View Post
                    Yeah, this is kind of ambiguous. Were you able to identify a PS_ON (or equivalent) pin? Did it always stay at the same voltage?

                    There are several different designs; I'd say that on 75% of TVs the PS_ON signal goes high to turn the TV on. On others it is labeled Standby and goes low when the TV is turned on.

                    PainBill
                    On my 42" The delta DPS284AP this pin (Pin1) PS_ON seems to be standby when it is high. (Service manual indicate it go to 3.3V) and causes the relay to turn on which removes 110V but leaves the 5V running from another source, which is the small switching transformer. Thus it seems to be off when high and on when low. My PS however being partially dead, just staying off.
                    Not supplying chopping freq to the 2 Driver transistors and no reponses from the OPTO couplers. I am not sure how they manage to regulate the 12V and 24V independent as they come off the same transformers.
                    I am thinking chip bad on mine, but not seeing any info on it, perhaps it burned the logo right off the chip before it died.

                    Comment

                      #11
                      Re: VIZIO XVT373SV Not powering on

                      The standby voltage was at 5.1 V all the time (with the power cord plugged in). It never changed when the power button was pressed. Every other pin was at 0V and did not change at all anytime. I was testing at the point where the power supply starts to feed wire to the main board. Is there any other ways I should go about testing?

                      From what I am seeing, it seems as though the PSU is not supplying any power to the Main Board other than standby power. Now to me that seems like a power supply issue but I am not sure.


                      edit: I was not able to find a "PS_ON" pin or anything like that name. I will have to open it up again to see exactly what the pins were called but I know one was 5.1VSB (which I assume was standby) and one was labeled 12V. the others i am not sure about
                      Last edited by UTbaseball36; 11-09-2011, 08:27 AM.

                      Comment

                        #12
                        Re: VIZIO XVT373SV Not powering on

                        Ok now that I had time for more study here is what I fond.
                        Pin 1 pson was mwant to go high when set demands power. The relay seems to click but is bringing higher current onlyn when mainboard calls to turn on. With it on U601 is supposed to switch on and run 12 and 24 power. There is a foil runniung from a SMT and on 1 side from AC ground I get 12.8V however nothing going to the chip. I tried a 1000 ohm resistor to try to drive it and discover it is koading that down so the chip must be shorted and failed.
                        Sadly I think it got too hot in its past life, so I can't make out any value on it, so all hope to revive it seems lost.

                        Haven't found a reasonable source for the part, but After google I was able to find a generic ASTEC supply that may be capable to run this set. I won't need the -12V part, but figure I can make up for standby using a relay and transistor and handfull of parts to simulate standby from the mainboards control line.
                        The pricetag of the ASTEC unit is only $30.00 plus shipping, so figuring 45 still cheaper than the 60 plus that anyone wants for the factory part.

                        And if there are further problems with the mainboard then I can either keep or return the supply since it has terminal strip outputs.

                        However if anyone knows the part number for this IC601 I would prefer to try replacing it, and then possibly the SMT part would bring in the power to it that it requires to get the supply working again.

                        The last confusing part is this. There appears to be 2 identical 24V outlets and a white cable comes off the board leading to nowhere.
                        I found the 1 cable going to the DC-DC FL tube convertor which is a black cable. Anyone know the purpose for the white cable? Test lead ??
                        There is just no place to hook it up to. Makes no snese at all.

                        My PS is DPS 284AP for the 42" series.
                        My Vizio is XV42 series but they all seem to work the same excepting wattage abilities.

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