Vizio M421VT LED no display

[budm]

Re: Vizio M421VT LED no display

That is really strange, so you are getting 40V at the +/- pin of the bridge as before. I do not see what else can cause that voltage to be that low.

[ryan74]

Re: Vizio M421VT LED no display

I only get 40v pulse for a second when I first turn it on then it drops to 0v almost instantly. Iam thinking maybe a short in lighting so it doesnt even hit full voltage before it shutsdown but im guessing at this point. All that is left is led lighting, main board, or a tiny board above main board that is wired to panel frame. It is possible I ordered a bad board from ebay but I have the same symptoms as with old board. I think I will ship back the pc and power boards I ordered.

[budm]

Re: Vizio M421VT LED no display

That can be the possibility that the used board is bad. Did you get it from Shopjimmy?

[ryan74]

Re: Vizio M421VT LED no display

pc board i tried was from shopjimmy. power supply was ebay. shopjimmy is out of stock on power supply otherwise I would order from them.
Im willing to reorder a power board but I don't know who is reputable. About 30% of my ebay purchases end up bad.
If anyone knows a relaible parts supplier that has 080GL1927LT power board(for a reasonable price) please share.

[ryan74]

Re: Vizio M421VT LED no display

This is the only board I can find in stock and I think there based in china and affiliated with aliexpress. I dont know if these guys are reputable.
http://www.buyqual.com/3pcgc10021a-r...27lt-lips.html

The pics below are of the led and cables for backlight. The site I got the pics from listed the same panel but a different model tv(M421NV).

[budm]

Re: Vizio M421VT LED no display

I ran out of idea on what to check next.

[ryan74]

Re: Vizio M421VT LED no display

I may buy the used led kit I found for $45 just to plug into power supply and try.
They list a different model tv but the panel number LC420EUH match.
I assume this will work but
Do the numbers in brackets matter? such as (SC)(A1)?
The reason I ask is the wires in pic above are different colored(red,blue,white,grey) than mine(blue,white,grey). The connections look correct. I think everything is the same except their red wire is grey on my panel.

It is alot more work to open panel to check. Im hopeing this can be used to bypass led's in my panel. If the tv powers on and the new led's go on, then I know I have to open panel and replace led lights.
Or should I just try another power board first.
Opinions?

[cmpeng]

Re: Vizio M421VT LED no display

Have you made any progress on your M421VT?

[ryan74]

Re: Vizio M421VT LED no display

I tried another power board and everything works.

[smithtv]

Re: Vizio M421VT LED no display

We have two M421VT tv's that have no back light, but have video. On one the Vizio led blinks 96 times before it stops and the other blinks 36 times before it stops. After each one stops blinking we can press power and get video, but no backlight. We have voltages on the connectors similar to what you reported.

Are you reporting that the problem on yours was solved by replacing just the power supply? Can you tell me the part number on the supply?

[willburn]

Re: Vizio M421VT LED no display

I am also having a problem with this model vizio.....I do not want to hijack, but last member seems done with his problem...

My problem is the power buttons and remote do nothing.....tv does nothing. When I plug it in, the vizio logo lights white, but does nothing else but stay on white, no change and power button does nothing, only way to turn off unplug. When I plug it in again, or reset it "hold power button 1 min unplugged, plug in power on" it does nothing to help.

so I tested the voltages at the power supply board and all my voltages are WAY OFF or non existant.

I find mainly 70v across board components on hot side everywhere,
The clips are only giving me 3.3v and 5v where designated, where the clips are labled 12v and 24v, I get no voltage, I am not getting any on vled or power_on either, so I am thinking it is the power supply board....

can someone help me test through it real quick?

I am an electrician/computer engineer repairing it myself.....

Donations will follow.

[kevin009]

Re: Vizio M421VT LED no display

How I ended up fixing mine

I also have the Vizio M421VT television set. I lost video and sound at the same time while watching a movie off of my Blu-ray player. I tried power cycling to no avail all I got was a blinking Vizio logo no sound, no picture of any kind, and no backlights. I had a tech company come out to fix my TV they replaced the power board and mainboard which did not resolve the issue. They put my old parts back in and said it was an unrepairable panel issue. I was not happy about this I called them and asked them to come out again and try replacing the T-con board, but they insisted it would not fix the issue I had, so I was on my own.

I replaced the T-con board myself got a recertified one from vizparts.com and the TV is working again like new. I had to send the first T-Con board they sent me back it only partially worked I had ghosting, and blocky horizontal lines on the picture, but I had some video and audio so I had hope. The second T-Con board they sent me was good. I am posting this because a lot of the information out there says if you lose audio replacing the T-con board won't resolve the issue well it does in this TV. It seems if the T-con board fails completely in this model TV you lose audio, video, and the backlights hope someone else with this model TV gives it a shot before trashing it worth the shipping cost of the part if it doesn't.

[bartendersimon]

Re: Vizio M421VT LED no display

I am also having a problem with this model vizio.....I do not want to hijack, but last member seems done with his problem...

My problem is the power buttons and remote do nothing.....tv does nothing. When I plug it in, the vizio logo lights white, but does nothing else but stay on white, no change and power button does nothing, only way to turn off unplug. When I plug it in again, or reset it "hold power button 1 min unplugged, plug in power on" it does nothing to help.

so I tested the voltages at the power supply board and all my voltages are WAY OFF or non existant.

I find mainly 70v across board components on hot side everywhere,
The clips are only giving me 3.3v and 5v where designated, where the clips are labled 12v and 24v, I get no voltage, I am not getting any on vled or power_on either, so I am thinking it is the power supply board....

can someone help me test through it real quick?

I am an electrician/computer engineer repairing it myself.....

Donations will follow.

Im having the same problem you have, did you get it fixed and how?

Thanks

[budm]

Re: Vizio M421VT LED no display

"I find mainly 70v across board components on hot side everywhere," That is because the wrong GND ref for the meter is used, you do not use chassis GND as the GND ref for the meter, when you are making measurement the primary DC side of the circuit, you use the negative leg of the main filter cap as the GND ref.
@bartendersimon, did you do any Voltage measurements on the power supply board?
Please up load good clear pictures of YOUR TV by showing the whole back sdie of the TV so we can see all the boards, and then the pictures of each boards, that will be the start.