Backlight Out but can see picture with flashlight Vizio E320-B2

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Vizio Television

Repair guides and support for LED, LCD, HD and other Vizio TVs.

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Jon Stombaugh @jonstombaugh

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Опубликовано: 30 мая 2020 г.

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Backlight Out but can see picture with flashlight Vizio E320-B2

When turned on the Vizio logo comes up dim and flickering and then appears to turn off. The picture can still be seen with a flashlight on the screen. Sound is fine. Based on what I’ve read it is most likely the power supply or the backlight but I’m not sure how to test or what parts to order. Included below are pictures of the boards.

I have a multimeter but not sure what I should be testing. Any help is greatly appreciated!

EDIT: Voltage Measurements of CN3 pins:

Turned Off

25 mV
7.3 V
20.3 V
36.5 V
50 mV
1.7 V
7.1 V
20.3 V

Turned On

1. 50 mV

2. 16.3 V

3. 30.5 V

4. 47.2 V

5. 40 mV

6. 19 mV

7. 16.2 V

8. 30.7 V

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jayeff @jayeff

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hi,

I don’t know the TV but if you only have a multimeter, locate the LED power connector on the power board and test the voltage there.

If it is >220 VDC then I suspect that the problem is in the backlight strips as there is no current flowing through the LEDs and you are measuring the open circuit LED voltage supply from the power board.

If it is <50 VDC then most probably it is in the power board.

Be safety aware when testing as there is exposed lethal voltage on the power board. Also ensure that the meter’s test probes do not accidentally bridge across any connections shorting them out and causing more problems

Alternatively, if you’re not comfortable working near lethal AC voltage, it may be safer to get a TV backlight tester - example only and use that to test the backlights

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Thanks for the response I will try this and report back. Any advice on locating the LED power connector on the power board?

31 мая 2020 г. из Jon Stombaugh

@Jon Stombaugh

In the 1st image you posted it looks like it is the one at the lower right side. Moreso as it has a high voltage symbol on the board next to the connector ;-)

The cable should disappear into the panel.

There are videos on YouTube on how to test the backlights using a DMM and a backlight tester

31 мая 2020 г. из jayeff

Thanks for the info! I checked all the pins on the connector in the bottom right (with the high volt symb, CN3). I checked the voltage of all of them with the TV plugged in turned off and turned on. I watched a number of videos of people checking the power supply but none of them were my model. I haven't yet been able to find any documentation on what the voltages should be. Based on what you've said though it appears that the power supply may be bad? I'll include the measurements below (There were some pins that were hovering between 20-100 mV. Should I just consider those as 0?) Thanks so much for your help so far. Should I just buy another power supply board? I'll include measurements in comment below EDIT: I've tried to mpost measurements in another comment but they are not appearing..... EDIT2: added meas. to original post

3 июн 2020 г. из Jon Stombaugh

@Jon Stombaugh

I can't find a circuit for the power board so maybe you could try a new one -(find a supplier with a no questions asked returns policy or at least a returns policy that will minimize the cost if the PB is not the problem) as it may also be the mainboard not telling the power board to turn on the backlights.

3 июн 2020 г. из jayeff

Got a new power supply board, plugged it in and...same problem. Vizio logo comes up dim when turned on and then flickers/fades to darkness. Pretty sure I hooked it up right as there are only a few plugs and not at much I could mess up haha. Guess I'll go ahead and return the power supply board. Any advice on next steps I could take to diagnose the problem? Seems a shame to scrap the TV though I understand I guess sometimes it's not worth it. Thanks for your help thus far. Any point in trying a new mainboard??

9 июн 2020 г. из Jon Stombaugh

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Thanks for the response I will try this and report back. Any advice on locating the LED power connector on the power board? — Jon Stombaugh
@Jon Stombaugh

In the 1st image you posted it looks like it is the one at the lower right side. Moreso as it has a high voltage symbol on the board next to the connector ;-)

The cable should disappear into the panel.

There are videos on YouTube on how to test the backlights using a DMM and a backlight tester — jayeff
Thanks for the info! I checked all the pins on the connector in the bottom right (with the high volt symb, CN3). I checked the voltage of all of them with the TV plugged in turned off and turned on. I watched a number of videos of people checking the power supply but none of them were my model. I haven't yet been able to find any documentation on what the voltages should be. Based on what you've said though it appears that the power supply may be bad? I'll include the measurements below (There were some pins that were hovering between 20-100 mV. Should I just consider those as 0?) Thanks so much for your help so far. Should I just buy another power supply board? I'll include measurements in comment below EDIT: I've tried to mpost measurements in another comment but they are not appearing..... EDIT2: added meas. to original post — Jon Stombaugh
@Jon Stombaugh

I can't find a circuit for the power board so maybe you could try a new one -(find a supplier with a no questions asked returns policy or at least a returns policy that will minimize the cost if the PB is not the problem) as it may also be the mainboard not telling the power board to turn on the backlights. — jayeff
Got a new power supply board, plugged it in and...same problem. Vizio logo comes up dim when turned on and then flickers/fades to darkness. Pretty sure I hooked it up right as there are only a few plugs and not at much I could mess up haha. Guess I'll go ahead and return the power supply board. Any advice on next steps I could take to diagnose the problem? Seems a shame to scrap the TV though I understand I guess sometimes it's not worth it. Thanks for your help thus far. Any point in trying a new mainboard?? — Jon Stombaugh

Vizio Television

Backlight Out but can see picture with flashlight Vizio E320-B2

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