Motherboard: NEW90 L21 No LED Backlight on Display

[Reech]

I can faintly see image on the display with flashlight but screen has no brightness at all. Laptop was dropped; replaced the power jack and LED display cable. Both were damaged and the left hinge was snapped off and flopping around. The LED cable must have shorted something since the display was working prior to the repairs.
The 2 fuses on back of the LED display check good.
I could not locate any other fuses on the motherboard.

[selldoor]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Double post _ double post

[dj_ricoh]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

first find the schematic
2nd what voltage you got on the ribbon connector from lcd

[Reech]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Sorry for the double post but I couldn't find any answers to this issue.
Can't find a schematic. I'll take some pics of the mobo, top and bottom.
Thanks

[khaahk]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

become friends with google, it took me 30 seconds.
https://cdn.badcaps-static.com/pdfs/...efbeaa87f2.pdf

[Reech]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Wow the schematic is great! Wish I could decipher where the fuses would be.
I am attaching to pics of the mobo hopefully someone could lead me to the fuses. Thanks

[Reech]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Sorry, here's other side

[khaahk]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

first ones to check - L12, L13

[dj_ricoh]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

that is a normal led screen.
the only difference in this led screen and a ccfl its the tube.
yours got a led stripe.
find a smash and test like that.
don`t open the mobo and start poking around

[MDY]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Did you check KBC? It send sime signals to LED screen...

[Reech]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Thank you to all for the replies, much appreciated!
kkaahk, I will check L12, L13 (are they top or bottom of board?) Any directions appreciated.
Dj Ricoh, what do you mean find a smash and work like that?
MDY, are you saying KBC (key board connector?)

[dj_ricoh]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Test the mobo with another screen.

[Reech]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

I don't have another screen to test. I am also not that high a level as you all seem to be at re: testing and probing these tiny components.
Not sure where to test the voltages going to the screen.
There must be something either the led backlight or voltages to it or a fuse along the way that was shorted at some point. As I said it boots great, you just can't see anything since the backlight is not functioning.
If it's the mobo it's just not worth the $$$'s at this point.
Thanks to all for your great replies! Much appreciated!!!!

[Reech]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Khaahk, I checked - L12, L13 and they check for continuity.
Are the L s the fuses?
Thanks

[selldoor]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Can you stop one of these threads running - looking through them both is very time consuming.

[khaahk]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

The L-s should be also working as fuses, they are ok. Power on the mainboard and do some careful voltage measurements (not to touch other pins while measuring or you might end up with dead mainboard) with the panel attached and power turned on.
Start counting the pins from the white triangle (right to left).
1-3 - should be adapter voltage
4-6 - should be 3.3V (which you have or else you would not see any picture on panel)
7 - should be also 3.3V (on stby also)
8 - maybe 1.5-3V (depending on screen brightness setting)
9 - should be above 2V
12 - not sure above 2V maybe digital signal, here should some info about brightness also

Write back the results, lets see then.
You also might have broken backlight on panel...

[MDY]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

I have the same problem. Can you post that tension you have on screen conector on pin 1,2,3,,36,38,39,40?

[Reech]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

selldoor, I just spent `15mins searching on how to stop/delete a thread and cannot find anything. I will try again later, Thanks

[selldoor]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

You Cant !! What you can do is put a post on saying please put
any future replies to ...... and put the link in for the other thread.

If you want to make a good job of it copy and paste the questions and answers
from the thread you are stopping to the thread you are keeping.

[Reech]

Re: Motherboard: NEW90 L21 No LED Backlight on Display

Closing this thread, please post to:
https://www.badcaps.net/forum/showthread.php?t=34610