Asus Laptop N550JK eDP Port Backlight bad Repair

[richi]

Hello,
I haven't had a little odyssey with my laptop. First was the display cable with a sporadic defect. I exchanged the cable and unfortunately the display broke  on the inside or on the back when I removed the plastic frame. The original was lp156wf4 and today I installed a B156HAN02.3. And as luck would have it, the connector on the display kept slipping out during installation. So I tested the whole display without the case and it worked.
It then happened on the 3rd installation attempt.... when the cable was plugged into the mainboard, the laptop was obviously started and there was a short circuit with sparks. But who takes out the battery when you want to test.
Now the new display is functional, but I have hardly any brightness. I usually set the brightness to minimum under windows, everything seems ok, one level higher it also gets brighter. But from the 3 level it gets darker again. And also the old cracked display shows the same behavior when I plug it in.
It seems to me that the supply voltage for the LED collapses or it is the PWM signal.

There is no scorched component visible on top of the mainboard.
I assume that a converter for the LED lighting is installed somewhere on the mainboard and that it is defective.
Does anyone happen to know the Asus board for the N550 series and can help here?

the short circuit was in the J4501 in the area of the first pins. Is pin 6 the PWM?

How would you go about fixing that? If something is on the underside of the board, I can't test it when it's dismantled. What voltage should be applied to Backlite Power?
Oszi Rigol is available but becomes difficult to control and measure without 5 hands.

[richi]

now a little update, i have now found Time for fix it :-)

I have remove mainboard, and i found a burn out coil.

I found on internet 2 sites who have fix it.. but with different  values.
there was also talk that it doesn't matter and is only for protection and that it also works with a wire bridge.

What values should the coil have? 120ohm 3A or 220ohm 3A or other ?