After change screen no video

[MDY]

Hi,

After change screen maybe with battery on, no video on screen. I do have video on VGA out. Screen is LED 40 pins. What can I check on it? I do have 19V on LVDS cable.

[dj_ricoh]

Re: After change screen no video

the cable its bad
p.s. did you saw sparks? if not your ok. i know that case but it makes sparks then your f k

if it makes sparks it will not even power

[fddizon]

Re: After change screen no video

dj,

y sparks happen?

[dj_ricoh]

Re: After change screen no video


i change the mobo then ( the problem then it had no backlight and i forgot the bat on)
dude i`m sorry for you. if you manage to fix it i wanna work for you as a apprentice.

[lefos]

Re: After change screen no video

Have you checked for any fuse near the lvds connector? Does it have picture but no backlight?

[kisk]

Re: After change screen no video

What is the laptop model? Were you changing a cracked screen or a different screen with no picture?

[Francisco.s]

Re: After change screen no video

Hi,

After change screen maybe with battery on, no video on screen. I do have video on VGA out. Screen is LED 40 pins. What can I check on it? I do have 19V on LVDS cable.

Probably the sio (embedded controller) has died. Usually the pins that control brightness, have no serial protector resistance, (connected directly) so current trough this pin became extremely high, destroying this sio output.
Try to cut this trace, and supply a fix 3,3v at connector brightness pin.
The schematic will help.

[MDY]

Re: After change screen no video

Thanks to all for replay. I do have image, but no backlight.

I checked datasheet of screen LP156WH4 and I have:

pin2 3.3V
pin3 3.3V
pin4 3.3V

pin 36 (LED_EN) 0,26V
pin 38,39,40 - 19V

I think problem is pin 36 (LED_EN) 0,26V. I checked the same pin in motherboard and I have the same 0.26V
I think in this pin I should have 3V to enable backlight on/off, right??

[Th3_uN1Qu3]

Re: After change screen no video

Yes exactly. I have the exact same problem with a Lenovo X200 that someone brought in a couple days ago. The backlight died after a water spill on the board. I have managed to fix the 20v power trace (a fuse blown and some corrosion), but i have LED_EN shorted to ground, so still no backlight.

I'll let you guys know if i manage to fix it.

[Th3_uN1Qu3]

Re: After change screen no video

I did fix the Lenovo - i lifted the BACKLIGHT_ON (aka LED_EN) pin from the display connector and wired it to 3.3v from somewhere else on the board. The laptop lost ability to turn the screen backlight off but that's better than no backlight at all. It does turn off when the laptop is put into sleep or shut down, so that's good enough. It's back to the owner now.

[nickscott818]

Re: After change screen no video

I had the same problem when I had replaced the sony vaio screen. It was not showing anything on the screen. I double checked the wires again found that the cable connecting to the mother board was out.

[MDY]

Re: After change screen no video

Hi Th3_uN1Qu3

I found that pin 34 is System PWM Signal input for dimming and also has to have 3V

By the way, what did you put on the cable to aislate?

[Th3_uN1Qu3]

Re: After change screen no video

Hot glue.

[MDY]

Re: After change screen no video

Hot glue.

Yesh, but do you use this one? http://www.leroymerlin.es/img/r25/04...2218640_ls.jpg

[Th3_uN1Qu3]

Re: After change screen no video

Something like that.