Vizio M261VP no Backlight!

[XmouseX]

Ok so I am working on a Vizio M261VP for my master bedroom. I found that it will power up, but there is no back light. I have checked all the fuses, looked for bad capacitors and tested the voltage regulators. I am so lost....This is the first LED TV I have worked on. Please someone give me direction, because I am out of Ideas.

[MisterD]

Re: Vizio M261VP no Backlight!

Go to the first page of this forum and look on the right side where it says "search this forum" and type in No Backlight, see what you can find from others that have posted this type of problem, other than you can wait and see if anyone replies. Good Luck

[XmouseX]

Re: Vizio M261VP no Backlight!

I always search the forum first...I cannot find info on this thing anywhere...

[XmouseX]

Re: Vizio M261VP no Backlight!

Ok. So I found that the backlighting cable has only 0.6V going through it. I am sure this is not enough. So I have back tracked to a (what I believe to be)voltage regulator. It has a input, ground and output. With the TV on, the input reads 19V and the output reads 0V. The number on this regulator is 540N. I can not find any information on it. Any help would be appreciated. thank you!

[smason]

Re: Vizio M261VP no Backlight!

Which cable? Careful measuring! The actual cable going to the lights is over 700v.

Pictures would help. The first 2 things to check if you have no backlights is supply voltage to the inverter board (usually 24vdc) and the BL_on signal (the main board telling the inverter board to light 'em up)

[XmouseX]

Re: Vizio M261VP no Backlight!

Ok, so on this TV, there is just a main/power board, a T-Con board and a board that has the LED lights on it.

[budm]

Re: Vizio M261VP no Backlight!

Any good clear pictures of the boards?

[XmouseX]

Re: Vizio M261VP no Backlight!

Here it is...I hope these pics are good enough.

[XmouseX]

Re: Vizio M261VP no Backlight!

Bump...I really am stuck on this one

[budm]

Re: Vizio M261VP no Backlight!

OK, this thing uses LED backlights.
Need good clear and focused pictures in circle, that is the LED backlights power supply.
Also good closed up pictures of all the connector of that same board.

[smason]

Re: Vizio M261VP no Backlight!

OK I'm reeeeally tired, but I see no power supply. Is it an external supply?

[budm]

Re: Vizio M261VP no Backlight!

It uses AC adapter since LED's do not draw too much current.

[XmouseX]

Re: Vizio M261VP no Backlight!

Ok so the picture of the(what I think is) voltage regulator 540N. It has 19V on the input and 0V at the output.

[smason]

Re: Vizio M261VP no Backlight!

It uses AC adapter since LED's do not draw too much current.

Wow 3 times through this thread and I finally noticed he DID say LED.
Need sleep. Bad.

[budm]

Re: Vizio M261VP no Backlight!

OK, the pictures are not focused enough for me to read the P/N on the components or traces. I am trying to look and see if there is any surface mounted fuse for this switching power supply for the LED strings.

[XmouseX]

Re: Vizio M261VP no Backlight!

I can answer that for you The surface mounted fuse for the backlight power supply is next to the other one which are located where the AC adapter plugs in. They are both good. As far as the pins on the on the mosfets. The mosfet in the upper left of the picture read 0V - 19V - 0V left to right. The mosfet located in the right lower hand reads output -19V, Gnd - 0V and input 19V.

[XmouseX]

Re: Vizio M261VP no Backlight!

P/N for thos IC's is 9998LN. Also there is no voltage present on the lower 2 caps. There is voltage present on the large upper caps.

[budm]

Re: Vizio M261VP no Backlight!

Need to locate the spec sheet for the IC next to see how they are used.

[XmouseX]

Re: Vizio M261VP no Backlight!

I will start looking. Do you find it weird that the mosfet only has input power?

[XmouseX]

Re: Vizio M261VP no Backlight!

http://eletranton.en.alibaba.com/pro...al_9998LN.html - this is all I found