VIZIO VT420M back light/no picture

[mpbarber]

Re: VIZIO VT420M back light/no picture

To measure the voltage on the fuse, power up the TV and set your meter to DC volts with the black meter probe connected to chassis and red meter probe to the fuse. Check the voltage reading at both ends of the fuse.

Hello,
I measured 0.91 - 1.01 volts on both ends of the fuse. Shouldn't it be 12 volts?

[budm]

Re: VIZIO VT420M back light/no picture

As already indicate in my Post #14, the main board is not sending 12V.
We will need good clear pictures of the main board, especially around the LVDS connectors to locate switched MOSFET that supplies the 12V to the T-CON.

[mpbarber]

Re: VIZIO VT420M back light/no picture

Hello, Sorry, I'm not being very thorough reading the responses. I've attached some pics of what I believe to be the main board along with some close ups but not sure I've captured what you are asking for.

Please let me know if you want additional pics.

Again, I really appreciate your help and your patience while I try to give you the information you require.

[tvtimmy]

Re: VIZIO VT420M back light/no picture

Those are pic of the power supply. The cord going to the wall gave it away. The mainboard will have the HDMI inputs on it.

[mpbarber]

Re: VIZIO VT420M back light/no picture

Those are pic of the power supply. The cord going to the wall gave it away. The mainboard will have the HDMI inputs on it.

Sorry... try these.

[budm]

Re: VIZIO VT420M back light/no picture

Your pictures are not straight shot and clear enough to identify anything much.
There are many versions of the main board: https://www.badcaps.net/forum/attach...6&d=1534252651
I cannot see all the numbers on the barcode sticker.
BTW, you do know how to do SMD works, correct?

[mpbarber]

Re: VIZIO VT420M back light/no picture

Your pictures are not straight shot and clear enough to identify anything much.
There are many versions of the main board: https://www.badcaps.net/forum/attach...6&d=1534252651
I cannot see all the numbers on the barcode sticker.
BTW, you do know how to do SMD works, correct?

Here are more pics.
I don't know what "SMD works" is.
I can get close up pics if you can tell me where.... I don't know much about the names of the electronic components.

[mpbarber]

Re: VIZIO VT420M back light/no picture

I took a closer look at my photos and realized that by using the macro setting on my camera it focused on the surfaces that were close to the lens and blurred those that were further away.

My main objective here is to see if I can identify one particular board that should be replaced.

Any further help/advice would be appreciated.

[budm]

Re: VIZIO VT420M back light/no picture

Put everything back in place and have every thing hooked back up, then test the Voltage at point A, B, and C with ref. to circuit GND when TV is off and when power switch is activated.

[mpbarber]

Re: VIZIO VT420M back light/no picture

Great! Thank you! I'll get the measurements today.....

[mpbarber]

Re: VIZIO VT420M back light/no picture

Here are the measurements you suggested I make. Please let me know if there's anything else I can do.

Thanks again,
mike


ps Not sure the attachment feature worked but I have attempted to attach a pdf file with the measurement information.

[vinceroger69]

Re: VIZIO VT420M back light/no picture

Here are the measurements you suggested I make. Please let me know if there's anything else I can do.

Thanks again,
mike


ps Not sure the attachment feature worked but I have attempted to attach a pdf file with the measurement information.

i have added a picture in case people cant view the pdf im sure budm will confirm these voltages soon

[budm]

Re: VIZIO VT420M back light/no picture

Since you have about 12V on point 'B' on the bottom pin of the inductor, then you need to check the Voltage on the top pin of the inductor, if you do have 12V then you should have 12V at the T-CON fuse unless the LVDS cable is bad or just an error in your measurement. You can also check the resistance between the SMD fuse on the T-CON nad point 'B' it should show < 1 Ohm.