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Vizio TV E470VL SMPS Flucuation Output Voltage

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    Vizio TV E470VL SMPS Flucuation Output Voltage

    Would someone please help troubleshoot a Vizio 47" TV Switch Mode Power Supply with 5 volt output fluctuating voltage. The voltage fluctuates at 5 the volt output and at the Pulse Switch Modulating IC at VCC. I have the following notes:

    1. The 3 main filter caps all have approximately 167 volts steady
    2. I have replaced 4 mosfets next to what I think is called the inventor transformer (big black transformer) pictures attached
    3. I have replaced Fuse F102 with an equivalent
    4. I have check all diodes and caps and they seem to be ok
    5. I replaced the 431 chip at U201

    Pictures attached for reference

    thank you for your help!!
    Attached Files
    Last edited by SMDFlea; 01-21-2022, 02:27 AM. Reason: E470VL

    #2
    Re: Vizio TV SMPS Flucuation Output Voltage

    opto isolator(s)
    feedback sets the output, if the feedback is screwed then the output will be screwed.

    Comment


      #3
      Re: Vizio TV SMPS Flucuation Output Voltage

      Is F102 the main fuse? was it open (blown)?
      Have you tried replacing C104 & C105?
      Last edited by R_J; 01-20-2022, 04:35 PM.

      Comment


        #4
        Re: Vizio TV SMPS Flucuation Output Voltage

        F102 is not the main fuse. It was open. It is near one of the big filter capacitors, C809.
        My ESR meter shows C104 & C105 to be ok. Should I test with capacitance meter?

        Comment


          #5
          Re: Vizio TV SMPS Flucuation Output Voltage

          Touch up some of those solder joints.

          Comment


            #6
            Re: Vizio TV SMPS Flucuation Output Voltage

            Ok, I see which fuse it is, What voltage do you get on the 12 volt output? It is supplied by the same transformer so maybe it is loaded down and effecting the +5 volts as well.

            Comment


              #7
              Re: Vizio TV SMPS Flucuation Output Voltage

              I don’t think it is on. Can you tell me how to jump the pins to turn it on or is there another place I can measure that will accommodate your request?

              Comment


                #8
                Re: Vizio TV SMPS Flucuation Output Voltage

                It is hard to trace the circuit using pictures, I will guess there is a transistor that switches the +12 volts, likely the to220 next to C201.
                It would seem ic101 is shutting down, what is the number on ic101?
                The pin to turn on the power supply seems to be STANDBY, but I don't know if it needs to be grounded or taken to +5v with a 1k resistor.
                The ON/OFF pin seems to be for the backlight circuit

                Comment


                  #9
                  Re: Vizio TV SMPS Flucuation Output Voltage

                  I just measured, there is NO 5 volt or 12 output. The 5 volt was fluctuating from 3 to 4 volts but is now 0 volts. The big capacitors were at 167 volts they are now at 171 volts. I don’t know what happened.

                  Comment


                    #10
                    Re: Vizio TV SMPS Flucuation Output Voltage

                    When say Ic101, do you mean U101? If yes that is the pulse modulating chip. 00465R

                    Comment


                      #11
                      Re: Vizio TV SMPS Flucuation Output Voltage

                      Did that fuse you installed go open again? Yes that should have been U101, I think that is FSQ0465R
                      Last edited by R_J; 01-20-2022, 08:24 PM.

                      Comment


                        #12
                        Re: Vizio TV SMPS Flucuation Output Voltage

                        The fuse is good. I think you are correct Q0465R

                        Comment


                          #13
                          Re: Vizio TV SMPS Flucuation Output Voltage

                          If you have 165vdc on u101, pin 1 (drain) I suspect the ic is bad

                          Comment


                            #14
                            Re: Vizio TV SMPS Flucuation Output Voltage

                            Using a big cap for negative, red lead of multimeter to pin one of the IC, there is a huge fluctuation anywhere from 34 to 151 volts

                            Comment


                              #15
                              Re: Vizio TV SMPS Flucuation Output Voltage

                              I had the multi meter set incorrectly, the voltage is 170.1 volts

                              Comment


                                #16
                                Re: Vizio TV SMPS Flucuation Output Voltage

                                Check the u101 vcc voltage, if 0 check that zd104 zener diode is not shorted, Also check that R105 is not open
                                Last edited by R_J; 01-20-2022, 08:43 PM.

                                Comment


                                  #17
                                  Re: Vizio TV SMPS Flucuation Output Voltage

                                  It is a fuseable resistor at 0.10 ohms. Did You see my previous post 170.1 volts at the drain?

                                  Comment


                                    #18
                                    Re: Vizio TV SMPS Flucuation Output Voltage

                                    Originally posted by dholley View Post
                                    It is a fuseable resistor at 0.10 ohms. Did You see my previous post 170.1 volts at the drain?
                                    I edited my post after seeing yours

                                    You can check the voltage one each side of R102 (using hot ground, main cap negative) one side will be 165vdc the other side will be the ic's str voltage that supplies the internal vcc startup cell, this needs to be above +12vdc and usually around 20vdc
                                    Last edited by R_J; 01-20-2022, 09:04 PM.

                                    Comment


                                      #19
                                      Re: Vizio TV SMPS Flucuation Output Voltage

                                      VCC Fluctuates between 9 and 11 volts, zd104 is not shorted, r105 is not open testing in circuit

                                      Comment


                                        #20
                                        Re: Vizio TV SMPS Flucuation Output Voltage

                                        Originally posted by dholley View Post
                                        VCC Fluctuates between 9 and 11 volts, zd104 is not shorted, r105 is not open testing in circuit
                                        This tells me the ic is supplying the startup vcc but T201 is not supplying the run voltage.
                                        Check the voltage On D102 cathode, that should be around 20v

                                        Comment

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