Vizio M470NV Backlight

[Primez]

Alright, so I just picked up a Vizio M470NV TV sitting outside that someone left behind thinking "All hope is lost". I however am much more optimistic and figured it was something simple such as maybe a fuse.

The problem I am having is with the backlighting.
When turning the lights off I can see the picture while shining a light on to the screen. I also have no issues with sound. It seems that the only issue is with the backlights.

What I'm asking for is some assistance in pointing me into the right direction on where I can find the fuse for the LED power supply to find out of that's the issue or if I need to search deeper into the strips themselves? I'm hoping someone in the community has had experience with this TV.


-Thanks!

[XmouseX]

Re: Vizio M470NV Backlight

We are trying to figure the same thing out on my Vizio LED edge. I will let you know when we have a conclusion

[drpj23]

Re: Vizio M470NV Backlight

I've just messed with a M470.
The power supply should connect to a smaller LED driver board. There may be a smd fuse on that.

Also check the voltages coming from the psu to driver board and I believe there was also a ribbon from the main to the driver board; you can check that as well.

If for some reason you conclude its the actual strips (rare in my opinion), I do have those. (Though mine wasn't a NV).

[Primez]

Re: Vizio M470NV Backlight

Edit - Typo'd

[budm]

Re: Vizio M470NV Backlight

@XmouseX, I wonder if his board use that 540N regulator IC, if it does, then we ask him to take the voltage reading at the output pin for us!
Never mind, his board is way different than yours.

[Cosmo66]

Re: Vizio M470NV Backlight

I had a Vizio 47 inch lcd with the same symptoms. There were 2 bad caps and one blown small surface mount fuse on the inverter board

[budm]

Re: Vizio M470NV Backlight

You can disconnect the wires that go the the LED String assembly which are connected to the two blue connectors, per printed on the circuit board, it should have 145Vdc output, be careful not to slip the probe!
http://www.shopjimmy.com/vizio-0500-...upply-unit.htm
There are white connectors on the bottom row, look for BL_ON PIN and see if it has >3VDC on it, that pin is used for turning backlights ON/OFF, ON = >3vdc.

[Primez]

Re: Vizio M470NV Backlight

@budm - On the blue connectors, my readings across the pins are:
VLED: 114v
4-1: 12v
4-2: 10v
4-3: 12v
The voltages are the same for the other 3 "groups"

As far as the white connectors, they all have the proper voltages as well as the BL_ON pin is >3VDC

[budm]

Re: Vizio M470NV Backlight

BL_ON pin is >3VDC is good and it is turning on the power supply for the LED OK. So connected the LEDs cables back in and see if you will still have the 114V.

[Primez]

Re: Vizio M470NV Backlight

Sorry, that was with the cables connected.

[budm]

Re: Vizio M470NV Backlight

4-1: 12v
4-2: 10v
4-3: 12v

I will need to figure out what these voltage readings mean.

[Primez]

Re: Vizio M470NV Backlight

I have a feeling it is something with the LED backlights themselves and not necessarily a power issue. I don't think that voltage drop is the problem because it's pretty consistent throughout the plugs.

[budm]

Re: Vizio M470NV Backlight

4-1: 12v
4-2: 10v
4-3: 12v
The example of the voltage readings are done at the LED return connectors, you do have the VLED feeding the LED strings OK, the voltage on the return lines just do not look right. Need to see how they do the current control of the LED strings.
Can you look and see how those 4-1,4-2, etc are connected?