Macbook Pro A1990 - No image or backlight - 820-01814

[Roccolade]

Hey!

I got this Macbook I’m working on. A Macbook Pro A1990 (820-01814) from 2018. It has no image – or backlight for that matter.

No history of liquid spills or anything. It's fully functional on external monitor - and the webcam works.. But it doesn't seem like the internal display is even detected in the settings.

The backlight has been lighting up a few times when entering recovery-mode.

I tested the panel on another Macbook, and the display worked perfectly. So, I know it’s well and working.

I get 0 volts on PPVOUT_S0_LCDBKLT. Tried diode-mode on PPVOUT_S0_LCDBKLT and got a reading of about 1950. I’m not I entirely sure what that tells me.

I really can’t figure out what the problem is. Can’t seem to find any defect components or anything.

All the best

-R

 

[2informaticos]

First of all, welcome to the forum!

Check presence of 3V3_S0SW_LCD and DP_INT_HPD, when LCD is connected.
Don't waste time searching for backlight, if no image yet.

 

[Roccolade]

Thank you sir!

I get 3.3V on both 3V3_S0SW_LCD and DP_INT_HPD when LCD is connected.

 

[2informaticos]

Check diode mode to ground on pins 1 & 3 of J8500.

 

[Roccolade]

Pin 1: 348
Pin 3: 495

 

[2informaticos]

For diode mode readings, there is big difference.
That points to damaged U9850; change it.
Be sure no corrosion sign on that side of J8500.

 

[Roccolade]

Thank you! I'll try changing the U9850 and get back with the result.