Vizio M261VP no Backlight!

[budm]

Re: Vizio M261VP no Backlight!

This is what I found so far, it is more likely to be OZ9998B, 4-STRING MADE BY O2MICRO.

I will see if I can download spec sheet that may show application notes which will show how to use it.

Try disconnecting that cable which is from the LED assemblies and see if you will get voltages at those caps.

[XmouseX]

Re: Vizio M261VP no Backlight!

With the cable unplugged, I still get NO power at the lower caps

[XmouseX]

Re: Vizio M261VP no Backlight!

What are your thoughts on the 540N mosfet?

[budm]

Re: Vizio M261VP no Backlight!

I just look at the picture of the board at shopjimmy:
http://assets.shopjimmy.com/media/ca...2600820150.jpg
Those two 3-pin device have designator as U9, U10 and they look like voltage regulator. The picture is not clear enough.
Can you verify or take close up pictures?

[XmouseX]

Re: Vizio M261VP no Backlight!

I have only 19V at the drain....0V on the other 2 pins

[budm]

Re: Vizio M261VP no Backlight!

Sorry, you are correct, they are regulator and it does have input but not output. I can see it has G, O, I around the pin?
So 'O' has zero volt?
Take the resistance reading between the Out (O) pin and Ground to see if it shows really Ohm reading.
It also looks like the IC's are driving the LED string directly.

[XmouseX]

Re: Vizio M261VP no Backlight!

here they are

[XmouseX]

Re: Vizio M261VP no Backlight!

10.2Mohms between (O) pin and ground.

[XmouseX]

Re: Vizio M261VP no Backlight!

In this photo you can see (IN) printed under the center pin.

[budm]

Re: Vizio M261VP no Backlight!

So the U9 (540) has 0V at the output pin, its output feed two low ohm resistors, and it does not show shorted circuit (10.2M Ohms reading). At this point, it shows that it is bad. Will have to find out what the output should be on this one. I will do more searching.
The U10, does have output, right? Will search for that part also.
Thanks for better pictures on your last post. I think you may have located the failed component.

[XmouseX]

Re: Vizio M261VP no Backlight!

Yes U10 does have 19V output.

[XmouseX]

Re: Vizio M261VP no Backlight!

Thank you very much for the help budm! It is always great to be able to get second opinions from like minds. You have helped me more than once

[budm]

Re: Vizio M261VP no Backlight!

I still cannot find out what this 540N 05L4 is yet!

[XmouseX]

Re: Vizio M261VP no Backlight!

All I can find is IRF540N

[budm]

Re: Vizio M261VP no Backlight!

Can you take another good picture around that 540N so I can see where the output pin is connected to? I can see two resistors but would like to see where they go to.

[XmouseX]

Re: Vizio M261VP no Backlight!

Hope this one works for you

[budm]

Re: Vizio M261VP no Backlight!

It looks like R22, 23 are current sensing resistors, they are pretty good size, and since they are using two of them, it means a lot of current is used. I can see that the output is feeding those two 9998LN IC's.
I still have no luck locating the 540N Regulator or the 9998LN LED driver ICs yet.

[XmouseX]

Re: Vizio M261VP no Backlight!

yeah. I love that Vizio uses un-findable parts.....I was trying to figure out what voltage I could inject into the output, but I need to find info on 540N in order to do that..

[budm]

Re: Vizio M261VP no Backlight!

https://www.badcaps.net/forum/showth...709#post280709
If we can ask him to see if it has 540N on his board, then he can take the measurement for us, he may even have the same failed 540N.
Never mind, his board is way different than yours.

[XmouseX]

Re: Vizio M261VP no Backlight!

Well I guess I should just look for the whole board? I am not having any luck finding that part...