Vizio M470NV - No Picture, but has sound backlight

[jortgonfreit]

I own a Vizio 47" M470NV that just decided to stop displaying anything on its screen.

There is still sound and it still has a backlight, but just no picture. I did take a flashlight to it just to be sure and no dice. It doesn't display anything when booting up, no logo, nothing. Also, when I change the volume or channel that display doesn't show up either.

I've read conflicting things across the internet and this site on this subject. Some say it could be the power board, others say it could be the mainboard. Has anyone had a similar experience with a Vizio TV?

I have not opened up the TV yet to look for any scorch marks or blown or swollen capacitors. I'm willing to take a multimeter to the boards to check it out, but does anyone have any idea where to start and what things I should measure first?

[CapLeaker]

Re: Vizio M470NV - No Picture, but has sound backlight

check out the tcon. since there is sound etc. maybe you want to borrow a oscilloscope and check out the LVDS signal. Then you know fast what's going on

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

I don't think there is a T-Con board. I looked and found nothing.

I only see a Main Board, Daughter Board, and Power Board. There's also a Wifi Board, a board for the Infrared sensor, and another board for the power button.

I've attached the main, daughter, and power boards. The main board has the wifi board attached to it at the top. All of these pictures are rotated so that the bottom of the picture is the part of the board facing the floor.

After taking a look at all of the boards I don't see any capacitors that are bulging or leaking. There are also no black spots on the board either.

What are some good next steps for troubleshooting this problem? I do not think I'll be able to get access to an oscilloscope.

[CapLeaker]

Re: Vizio M470NV - No Picture, but has sound backlight

Another pic of the whole back of the tv with everything connected, please.

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

Here you are.

You can see at the very bottom of the television what appears to be the infrared sensor board. And the very right of the television is the board for the power button.

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

That board at the bottom is a bluetooth board.

[CapLeaker]

Re: Vizio M470NV - No Picture, but has sound backlight

See the board in the middle of the tv with the big black heatsink? That's the t-con. With all the boards connected like it should be, check if the t-con gets any power (5V) from the PSU. Check fuses TF1 and F4 on the t-con.

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

I'll try that when I purchase a multimeter today and let you know the results.

I'm a bit confused why you call it a t-con board and it's called a daughter board here: http://www.shopjimmy.com/vizio-3647-...hter-board.htm

[TVRepairNoobie]

Re: Vizio M470NV - No Picture, but has sound backlight

Possibly the board has the T-CON chip on it. so, most would call it that.

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

When the TV is both on and off fuse f4 is around 5.14 volts.

When the TV is on fuse tf1 is 12 volts. It's zero when it's off.

[CapLeaker]

Re: Vizio M470NV - No Picture, but has sound backlight

both sides of the fuses?

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

Yes. Both sides.

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

I just decided to buy a new Daughter (or TCon) board off eBay. It was only $40 and if that fixes it then it was worth it.

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

So I swapped out the T-Con (or Daughter) board and still have the same issue.

What is the likely culprit at this point? I've got two options here. The main board or the power board.

[jetadm123]

Re: Vizio M470NV - No Picture, but has sound backlight

Try checking the 3 fuses on mainboard. I can't read the part number of U24 in the lower right corner of the mainboard. It might be a voltage regulator. Check it's output voltage.

[CapLeaker]

Re: Vizio M470NV - No Picture, but has sound backlight

borrow a 100Mhz oscilloscope and check the LVDS. This makes sure that either Video is or isn't coming out of the main board.

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

Say I get an oscilloscope to measure the LVDS signal. What exactly am I looking for and how would I measure this signal?

[CapLeaker]

Re: Vizio M470NV - No Picture, but has sound backlight

What you do is to turn the TV on and probe the LVDS connector on the mainboard. Not on all pins is the LVDS carried, but you will find it no problem. Now take the remote and turn the menu on and off all the time while probing the LVDS connector and if the mainboard works, you will some pins on the connector that will change the signal on the LVDS each time you press the menu on and off.

https://www.youtube.com/watch?v=WeYFzugvH4c

[jortgonfreit]

Re: Vizio M470NV - No Picture, but has sound backlight

Thanks for your help. I've located a place in my city that offers access to oscilloscopes. I'll test this out on Saturday.

If I am able to determine that this is the issue is there any way to fix it beyond replacing the mainboard entirely?

[CapLeaker]

Re: Vizio M470NV - No Picture, but has sound backlight

If you find that the signal changes each time you turn the menu on and off, that main board would be o.k. and the trouble lies further down the chain. Then do the same thing on the T-con board.