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Vizio TV E470VL SMPS Flucuation Output Voltage

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    Re: Vizio TV E470VL SMPS Flucuation Output Voltage

    In the attached picture these two MOSFETS, voltages seems weird, is it normal that when I measure in DC VOLTS at the drain, voltage starts out as high as 27 volts and lowers down to 9 volts?
    Attached Files

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      Re: Vizio TV E470VL SMPS Flucuation Output Voltage

      Are you using the neg. side of bridge rectifier or neg. leg of main filter cap for ground? either is ok when checking voltages in the hot side, use caution HIGH voltage on hot side.

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        Re: Vizio TV E470VL SMPS Flucuation Output Voltage

        Negative side of big cap

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          Re: Vizio TV E470VL SMPS Flucuation Output Voltage

          Not sure what we've covered, you do have around 160v on the big caps when in standby? powered up it should go up to around 390v.

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            Re: Vizio TV E470VL SMPS Flucuation Output Voltage

            Do you have a steady standby voltage or is it still 0?

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              Re: Vizio TV E470VL SMPS Flucuation Output Voltage

              Did you test the new zener diode before replacement?

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                Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                not sure, maybe test Q101 and 131, and test every resistor in that area, the values should all be marked see the tiny writing, make sure the ohms reading is close to the value marked on the resistor.

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                  Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                  Originally posted by nomoresonys View Post
                  Did you test the new zener diode before replacement?
                  Yes

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                    Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                    Originally posted by nomoresonys View Post
                    Not sure what we've covered, you do have around 160v on the big caps when in standby? powered up it should go up to around 390v.
                    167 volts on the filter caps

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                      Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                      Originally posted by nomoresonys View Post
                      Do you have a steady standby voltage or is it still 0?
                      No standby voltage, no output voltage of any kind

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                        Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                        Originally posted by dholley View Post
                        In the attached picture these two MOSFETS, voltages seems weird, is it normal that when I measure in DC VOLTS at the drain, voltage starts out as high as 27 volts and lowers down to 9 volts?
                        Any ideas why there is changing voltages on these mosfets? The mosfets just above them are steady and stable at 167 volts

                        Comment


                          Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                          Originally posted by nomoresonys View Post
                          not sure, maybe test Q101 and 131, and test every resistor in that area, the values should all be marked see the tiny writing, make sure the ohms reading is close to the value marked on the resistor.
                          How do test Q101 and 131 in circuit with a multimeter?

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                            Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                            yeah, i guess, see if its short, i believe you test drain to gate and drain to source, might be middle leg to each outer leg if continued beep or close to 000 in diode mode its probably shorted. Dont get it confused with both outer legs because they can show continuity and be ok. Prolly best practice is get the datasheet of the component to be sure of the pinouts.
                            Last edited by nomoresonys; 02-19-2022, 10:57 AM.

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                              Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                              There is only 1 volt at Q707 at the drain. Picture attached. For orientation it is right next to big filter cap, cap farthest away from input power. Any suggestions?
                              Attached Files
                              Last edited by dholley; 02-19-2022, 03:44 PM. Reason: Attaching photo

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                                Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                                make sure resistor R704 is ok, it looks beat up from the picture.

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                                  Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                                  I wanted to thank everyone for their help in trying to fix this power supply. I was not available to fix it an ended up buying replacement at BuyQual.com at a reasonable price.

                                  thank you and God's Blessings,
                                  Danny

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                                    Re: Vizio TV E470VL SMPS Flucuation Output Voltage

                                    well we gave it our best shot, thanks for update, it would probably be a lot easier to determine what's wrong with it now that you have a working board to compare with, thanks for the blessing, right back at ya.

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