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My display backlight switch off after a few seconds

Hello !

I have a display HP La2405wg.

When I power it on, it will display a few seconds, and then the backlight is turned off.

I can still see (barely) the display so I guess the LCD is working.

I was wondering what could it be ?

Best regards,

Frederic

Mise à jour (24/04/2018)

Hi !

I tried with and without computer (2).

OSD works a few secondes too, I can also see it a little (barely) after the backlight is gone).

I opened the display and checked the board.

Here are a couple of pics:

Block Image

Block Image

The area on "T101" (transformer) and 2 diodes (D101 and the one next) seems like it heated a lot.

I removed the 2 diodes to tests them. They seems alive.

I measured the both transformer and I can see similar impedance on both (measure in circuit).

I think this area is called the "inverter" but I dont know how it works: I'm in electronics engineering, but have very very limited knowledge on displays...

The driving IC (SO14 package) seems to be an OZ9938ON (from what I can read on it).

I found this: http://dalincom.ru/datasheet/OZ9938GN.pd...

The board seems to be this one:

https://goo.gl/KeTDGB

Any idea welcome :D

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Hi @raymong ,

Do the OSD menus work OK?

What make and model computer is the monitor connected to?

Have you tried it with another computer to prove whether the fault is with the monitor or the computer?

da

Hi sorry! I'm new on Ifixit too :) I wanted to answser and I updated my question instead ;)

da

Here is a picture of one of the backlight connector, there are 2 like this.

[image|1434147]

Any idea if I can check for shorts between some of those pins ?

da

Replaced two capacitors (680uF/35V) on the left side of second photos, it should be work.

da

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Hi @raymong ,

The 'heat' mark on the board may be caused by a problem with the "load" rather than a problem with the supply.

As your monitor uses a CCFL backlight perhaps this video may be of some interest

Update (04/25/2018)

Hi @raymong ,

No you cannot test it this way.

Without a schematic (or service manual) for your particular power board ( or monitor) the best that you can do is to replace the board.

I cannot verify if the board in the link you provided in your question is the same as yours as the link is down at the moment.

As long as the board number matches your board number exactly then you'll have no problems (hopefully- if the power board is the problem that is).

Did you look at the "video" that I posted in case your problem seems to be the same?

Good luck.

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Sorry for stupid question, I just noticed in the IC datashee5 that it's for CCFL

da

Hi @raymong ,

No questions are ever stupid.

Not asking questions when you don't know is stupid.

Cheers.

da

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Hi !

Here is a view of the backlight connector (if it helps for something).

Block Image

I measured open circuit between all wires...not sure it's possible to diagnose this way :(

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To fix your HP Compaq LA2405WG 24” lcd monitor you will need a backlight assembly, here is the link:https://www.ebay.com/itm/Samsung-LTM240C...

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