No Picture at all with Vizio M470VSE

[lottathought]

Hi all
I have been doing a ton of reading but I am still very new at troubleshooting this TV.
I have a Vizio M470VSE.
When I try to power it on, the Vizio Logo lights up. But that is all.
I am not seeing any backlights and if there is any picture there at all, I am not finding it with the flashlight.
It was on HDMI so I cannot tell if there is any sound..but I hear nothing.

I have tested the voltage on the Power Supply board.
I am getting 3.3v on standby and 12.5v when I power on. This seems to match the print on the board. It also seems to indicate that the Main Logic board is responding.

When I jump over to the led driver board (bypassing the TCON) .....
I believe that this only has 2 LED strips? One at the top and the other at the bottom? I read that someplace and it seems to match the wiring.

The connection coming off the LED driver board going to the led backlights has all black wires except for 2 Red ones. I am thinking that the 2 red ones are the + current for the two strips?
When the TV should be powered up and the Vizio Logo is lit up, I am getting 40v from these red wires.

I have not been able to find any info on what the test volts on what the LED driver board output should be....but the numbers seem to indicate to me that it is responding and sending a signal and power to the LED strips.
And I am guessing that all the previous boards must be working correctly to get me to this point.

So does it sound like LED strips?
Or have I missed something?

Thanks for any input.

[dskall]

Re: No Picture at all with Vizio M470VSE

When you say the Vizio Logo lights up. Do you mean the screen or the light at the bottom?
This appears to be edge lit with 2 strips. If you pull the led connector off and measure the voltage as soon as it powers on what do you get?

[lottathought]

Re: No Picture at all with Vizio M470VSE

When you say the Vizio Logo lights up. Do you mean the screen or the light at the bottom?
This appears to be edge lit with 2 strips. If you pull the led connector off and measure the voltage as soon as it powers on what do you get?

The Vizio Logo on the bottom of the TV frame lights up.
I see nothing from the LED strips. I have the back off and have confirmed from both the front and the back that I am getting no light.

I am guessing that you are talking about the two red wires going out to the LED strips?
These go up to 40volts when the TV is powered on...and hold there.

Actually....digging further, after I posted the question.... I found an old post.

The OP was having a slightly different issue ....but he was kind enough to post his test results for this model of TV.
They are listed in posting #3.

What caught my attention was the voltage he was seeing on those same 2, red wires (VLED wires), going to the led strips.
He was getting almost 60v.....where I am only getting 40v. (Like I said, I hold at a steady 40v)
In fact, not only did the red wires not match, my CsOuts were very low next to his too. (The remaining black wires from the LED Driver to the LED strips)

I went back and checked the power supply board connections to the LED driver and my results match his. (Or come very close)

So if my LED Driver board is getting the same input as his board...and my board output is low, across all the outputs, I would think it is a no-brainer to replace the LED Driver board.

BUT.......and this threw me.....he fixed his problem by replacing the main logic board over an eeprom issue. This was under the advice of ShopJimmy.

And this has me questioning where the LED driver board is being told how much power to put out.
(Now granted, he has much higher volts than me...so I may be overthinking this...)
But is this a case where the LED driver board is failing and is not delivering enough volts to cause the LED strips to light up?
Or...is this a case that the LED Driver board is not delivering enough power to light up the LED strips because the eeprom is stupid and telling it to not deliver enough power?

Oh..and if you are wondering what the wires going from the main logic board to the LED driver are getting in volts....there aren't any wires. It looks like any communication from the main logic board is routed back to the LED Driver board through the power supply board.


Here is his thread.
https://www.badcaps.net/forum/showthread.php?t=37387