MacBook Pro A2442, board 820-0298-A, no backlight

[survivalbloke]

I'm working on a MacBook Pro A2442, board 820-0298-A. This device was liquid damaged and had no power. After I repaired the liquid damage, I find the device powers on and works with external video, but backlight is not working.

Anyway, I really want to improve my fault tracing skills, instead of having to rely on others to always tell me where to look and what to check. In this case, I have a question about navigating schematics. If I wanted to trace the backlight power circuit, how do I find where that circuit begins? If I search for "lcd" in the schamtic, it is listed on many pages.

[mon2]

I think you mean 820-02098?

Check the voltage of PPVOUT_LUXE to ground.

[obelix24]

i will pin myself as i have same macbook with same issue. I've 0V on PPVOUT_LUXE

[obelix24]

survivalbloke have you fixed this ? i'm having same issue,.

[obelix24]

Ok so i found the problem 🤣 i was missing one resistor in backlight near UP800 (it was i think RP832). After adding this resistor backlight start working again.

[mymacdz]

I SUGGEST THAT YOU CHECK THE CAPACITOR

[PITERPENY]

on new devices all have a problem with the display tilt sensor. check first

[guruji]

hi i have the same issue with A2442, the resistor RP805 5V_s2_main the volateg was dropping and the impedance of ic was 15ohms which sure shot ic bad after replacing the 5V_s2 across the resistor RP805 was okay.The LUXE_ppvout now is 14V but still i dont see the backlight i see the apple logo for 2 sec and all blank while the laptop is still on.is 14V_okay for luxe_out.
thanks

[mon2]

LUXE_ppvout

???

[guruji]

Ppout_luxe for backlight I get 14.5v and still no backlight on.

[mon2]

PPVOUT_LUXE - suggest to cut & paste the exact netname from the schematic. Otherwise the label cannot be found.

Is this backlight rail stable?

Do you see the graphics on the display when the lid is opened?

Consider to review the lid sensor where the angle read by the sensor can consider the lid to be open or closed. This lid sensor does require calibration if the display assembly was replaced.

Watch this:

https://www.youtube.com/watch?v=M6TeqUQ26iE

and

https://boards.rossmanngroup.com/thr...-sensor.64047/

There are some techs on this board that own this tool and they can comment more on this topic.

[guruji]

The backlight supply remains stable and when I open the lid I hear the chime and see graphics but no backlight .the display assembly was not changed

[guruji]

ok finally i confirmed with another panel the problem is with the backlight inside the screen.

[lord]

Hi,
Also water damage induced backlight problem. I have checked with a known good board - and backlight works - so it's not the lid angle sensor or the lcd.
I have transfered all the components damaged from a known good board and checked all damaged traces and fixed them. Clearly am missing something. Can't find a short anywhere on the board so i'm thinking logic. Last thing i did was bought a new RAA209100B from LRF (it does not look the same as original but it is the same part number) - and still no luck. I then checked the feedback traces and current sense resistors traces which are all fine.

Clearly i am missing something... Any advices?
Did anybody order replacement RAA209100Band replaced successfully?

[mon2]

Measure the voltage to ground of IPD_LID_OPEN_1V8 @ UR330 / RR331. The lid sensor is a combination of the LCD display and the trackpad. Only if the lid is deemed to be open will the backlight enable.

[guruji]

Hi all
okay this is very a complex backlight problem they have a very thin led backlight circuit booster inside . I have finally opened the screen carefully and now will change the backlight board inside. Attaching photos so most of us know how deep we are going with this .
cheers

[lord]

Measure the voltage to ground of IPD_LID_OPEN_1V8 @ UR330 / RR331. The lid sensor is a combination of the LCD display and the trackpad. Only if the lid is deemed to be open will the backlight enable.

Hi,
Thank you for your answer and helping out.
As you requested I soldered a wire on pin 14 of the trackpad connector JT400: the voltage IPD_LID_OPEN_1V8 signal is 1.8V when the lid is open, and 0V when lid is closed. I mentioned that i tested the computer with a known working board and the backlight was working so i figured it must be a problem in the logic board, not the peripheral components. Do you agree?

[lord]

Hi,
Thank you for your answer and helping out.
As you requested I soldered a wire on pin 14 of the trackpad connector JT400: the voltage IPD_LID_OPEN_1V8 signal is 1.8V when the lid is open, and 0V when lid is closed. I mentioned that i tested the computer with a known working board and the backlight was working so i figured it must be a problem in the logic board, not the peripheral components. Do you agree?

Could it be the CPU? Anybody have datasheet for RAA209100B?

[guruji]

Finally this led backlight they have made controls every cell of the led on the board like when we switch on the apple logo you have only the center led come on and the. The entire backlight lights up .also the colour of the led is blue.now the only thing is a need the right tape to seal can anyone tell me which tape and the size
thanks all

[guruji]

Also if the lid sensor is disconnected the backlight will come