820-3787 no video

[jadao]

This board has no liquid damage, it chimes and fully boot i can see activity with pendrive, caps lock keyboard and the sound in osx when i press keyboard keys.

I have no image and obviously no backlight.
It is missing LCD_PWR_EN
All the following gpu sequence rails is missing:
P3V3GPU_EN
P1V8GPU_EN
GPUVCORE_EN
P1V35GPUFB_EN
P1V05_S0GPU_EN

Is there any common denominator to check or hopeless board?

Thanks

 

[JohnB8812]

Any history? Liquid damage drop etc?

 

[jadao]

No drop according to the client and the laptop body.
no water damage, i just noticed the screen looks like it's a replacement...but for now i don't have video, pramed the board still no video.

 

[2informaticos]

Did you try BIOS?
Do you get voltage on pins 28-30/J8300, at least first few seconds when power the board?
LCD_HPD should then go high.
Be sure to have compatible screen.

 

[jadao]

No I didn't try a bios yet.
I dont get voltage (0V) on pins 28-30/J8300 because LCD_PWR_EN is missing so no Vout on u8300.
I don't have image on external monitor also.

Should I still try a bios, or more things to check for gpu circuit?

 

[2informaticos]

You must check pins 28-30 of J8300 in the first seconds, when board is powered up.
LCD_PWR_EN should be high in that moment, even without LCD connected.
The voltage is maintained only if LCD_HPD goes high!

Reflow GMUX U9650...