[SOLVED]820-2936 backlight autogoal :(

[TheSkualo75]

Hi Rossmang Group,
today i have resolved an issue with a only one usb port. A bad usb cable, burn the L4600. Everything ok...donor board...solder...et voilà issue resolved..... but unlickly...connect the battery and my screwdriver fall in to the board...damn hell ....so backlight don't work... anyway i have this tensions:
ppbus_g3h before and after the fuse f9700=11.9v
bkl_en=2.9v
lvds connetor gnd /21= 19.9v
when the laptop restart after the chime, for a moment the backlight seems to want go on...but blink just a micromoment...
ps.i'm a newbie, don't beat me strong

 

[dukefawks]

Voltage on BKL_PWM?

 

[TheSkualo75]

thanks for your answer,
BKL_PWM is= 3v (mesured with multimeter fluke187, not oscilloscope at the moment)

 

[dukefawks]

This seems to be a dead backlight chip. What is the voltage on both sides of R0910?

 

[TheSkualo75]

tension btw r0910= 0volt
form gng to pin1 of r0910=12,151v
from gnd to pin 2 of r0910 = 12,151v

 

[dukefawks]

Yeah, I would say the LP8550 is dead.

 

[TheSkualo75]

Thanks Duke! When the LP8550 arrives to me, i will change and update the post if i resolve. Anyway, where i can find the correct voltage to diagnose the other things? thanks

 

[TheSkualo75]

Solved, i replaced lp8550! thanks a lot!!