Backlight problem Acer LA-031P

[grbo92]

Hi,

i have one acer Nitro 5 without backlight on my desk.

Mainboard model: LA-L031P GH53Z REV 1B

Attached schematics and boardview are REV 1A, slightly different as REV 1B.

11411_LA-L031P-Acer_Nitro_5_AN515-45_AN517-41-GH53Z_Rev_ (1).zip

Repair history: customer cleaned dust and changed thermal paste, shortly after that there was no light

Notebook boots without problem and shows only image without backlight, HDMI output working. Optical inspection done, no burned or broken components. Tested also with a new display module.

Voltages measured and noted on the attached image. Forgot to write ENBKL line on the image, is pretty low 0.05V

Would appreciate any help.

Thanks

[grbo92]

Just a quick update, the problem is SOLVED!

As i wrote earlier only available schematics for this model was a revision 1A, which is slightly different from our 1B. Because of that i have decided to trace the lines manually to EC and CPU to find the right ones. The ENBKL was first measured on the wrong spot, that is why it was pretty low.

After tracing the lines i was concentrated on the following two circuits ENBKL and INVTPWM. The ENBKL circuit was working without problems but i have found a problem on the INVTPWM line which wasnt 3.3V on the output. Input from the CPU on the pin 2 (INVTPWM_R) was at 1.8V but and +1.8VALW was also present just like the +3VS on the resistor. The problem was that the output pin 4 was partially shorted to the pin 3 GND.

So i lifted the pin 4 and borrowed the 3.3V from ENBKL line and the light came back to life.

[Fzero90]

Gracias por la información ,me sirvió y pude reparar mi notebook acer.

Thanks for the information, it helped me and I was able to repair my Acer notebook.