Vizio TV E470VL SMPS Flucuation Output Voltage - Badcaps

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dholley

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#141

02-18-2022, 05:58 PM

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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nomoresonys

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#142

02-18-2022, 10:16 PM

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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dholley

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#143

02-19-2022, 02:40 AM

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Negative side of big cap
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nomoresonys

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#144

02-19-2022, 05:51 AM

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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nomoresonys

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#145

02-19-2022, 06:21 AM

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

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

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#146

02-19-2022, 06:25 AM

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Did you test the new zener diode before replacement?
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nomoresonys

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#147

02-19-2022, 06:42 AM

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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dholley

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#148

02-19-2022, 06:51 AM

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Originally posted by nomoresonys

Did you test the new zener diode before replacement?

Yes
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dholley

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#149

02-19-2022, 06:52 AM

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Originally posted by nomoresonys

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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dholley

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#150

02-19-2022, 06:53 AM

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Originally posted by nomoresonys

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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dholley

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#151

02-19-2022, 06:59 AM

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Originally posted by dholley

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
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dholley

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#152

02-19-2022, 07:50 AM

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Originally posted by nomoresonys

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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nomoresonys

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#153

02-19-2022, 09:54 AM

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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dholley

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#154

02-19-2022, 03:42 PM

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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nomoresonys

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#155

02-19-2022, 04:26 PM

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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dholley

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#156

05-02-2022, 10:31 AM

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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nomoresonys

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#157

05-02-2022, 12:30 PM

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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