Acer Aspire 5742 backlight not working

i broke the LED screen of my acer aspire 5742. i replaced it with a new screen bought from ebay. now there is a picture but there is no backlight. before i installed the new screen, the backlight was working even with a cracked screen. Now the backlight is not working on both of the screens. Any ideas?

 

Try double checking the connections. If it's still dim, contact whoever you purchased it from for a replacement.

 

Hi, Just wondering if you fixed this as I have exactly the same problem?
Backlight worked on cracked screen so replaced with new screen now no backlight on either??

 

I also have exactly the same problem!

In an attempt to fix this I have replaced the power button board which I believe has the lid sensor, and also replaced the LED CMOS cable(cable from mobo to screen) Still no good!!

This is a laptop I'm working on for a client, and am getting a little desperate.

Help!!!!

Thanks!

 

What display model are you guys using?

 

I have the same problem on a 5742 also after changing the LED screen.

It seems that there is an issue when changing the screens similar to the dell 1545 that blows the fuse.. but unfortunately the 5742 doesn't use a fuse for the LED screen.

Here's what we have tried:
We have tested the (identical screen) replacement screen on another laptop and it does work fine.
Re-fitted the original broken screen and no backlight on that either. (there was originally)
We have tried a brand new screen cable also and this didn't make any difference.
We have the schematic for this laptop and have tested that there is voltage getting into the screen backlight.

The only thing we can think of is that the LED driver uses constant power in and throttles the grounding (probably with a transistor) out to allow for dimming.

Only problem is, we cant see on the schematic whats controlling the out!

Has anyone else found a solution or got any ideas?