Macbook A2442 820-02098 boot and display issue

[obelix24]

I've replaced U5000 with U5000 from M1 (a2338), recreated all missing pads now i don't have hotspot on U5000 and also all readings arround U5000 are fine.

But Macbook is behaving same (no backlight and only apple logo that bootloops)

[obelix24]

I was measurring with power connected and i or something shorted U8100 (there is short to ground on PP1V8_S2. After injecting 1V only thing that gets hot is U8100 (there is hotspot)

Does anyone know if U8100 can be replaced with U8100 from 2020 M1 a2338 (820-02020) ?

[obelix24]

ok i can;t use U8100 as it's different

[mon2]

No experience with this, yet. What are the topside markings of the original U8100 that was onboard? Post a pic or link to this device.

[obelix24]

It looks same problem is orientation. On 2020 a2338 is rotated so when i want put it on 2021 m1 pro the dot (first pin) is on different location

m1 pro (a2442) 820-02098 - U8100
APL1098 343S0051
N05FX2LOLM 2227

m1 (a2338) 820-02020 - U8100
APL1096 343S00438
POA4B000LL 2122

[mon2]

New Original A2337 A2338 APL1096 343S00438 Power Supply Chip IC Chipset - AliExpress 7

[obelix24]

yes i know it's same dimmensions but orientation and possition of pin 1 differs.

I will probably need to buy icloud locked board to have donor and comparission

[obelix24]

ok i finaly got some 16" m1/m2 pro's i've replaced U5100 and it's back to 20V but the problem remains ...

No Backlight and when screen is connected (JP600) it also reboots (there is bootloop - only apple logo (without backlight) and reboots)

Any idea ? what can cause that when screen is connected (via JP600) there is no backlight and bootloop) but when it's disconnected macbook works fine.

[obelix24]

Does anyone have Diode readings from JP600 ? I want to compare if there is something

[obelix24]

ok so it looks like this issue (bootloop + no backlight) is due to backlight issue on display (not on motherboard).

same issue :
https://www.facebook.com/Logicboard....UKu6sqpSVwqaol

[Stephen]

I just did a beautiful replacement on an A2442 LCD and restoring True Tone back with Pro Motion Display. The A2442 LCD was cracked and destroyed but the housing was fine, had to remove the original broken LCD, (ordered a genuine lcd replacement on AliExpress) those lcds due require you swap the two chips to restore True Tone and to make sure those pesky squares do not show up. I did it successfully with ease however the first time I had an issue with the backlight, I discovered that the backlight itself is very prone to failure, I learned that by purchasing another backlight on eBay (a broken A2442 lcd with a good housing and turns on) took off the faulty screen again and then popped in the new screen that already had the chips on. The backlight came back on. There was no mistakes made on that backlight, however it just seems that the backlight cable or the backlight itself could go out. I believe this will be a known flaw in these models over time. Sadly you cannot replace that backlight unless you remove the LCD first. And it is a very very veryyyyyy hard job to do when the LCD is not broken, if it is broken, then you can just remove with easy if you crack it here and there no big deal, but if you are trying to retain the LCD without cracking, you have to remove the rubber seals from the LCD that is underneath the LCD itself. Very very time consuming and risky. Replacing the LCD is the best option, just do not forget the True Tone and the chip that is married to the board. I wish you luck on this repair. It took me a few times to perfect it but its worth it once you figure it out.

[obelix24]

Only problem is i'm not aboe to find any cracked lcd for this macbook on ebay (in europe)

[obelix24]

ok so I got another a2442 that looks like will be not repairable so I decided to switch the board where I have backlight issues to see if it's really problem on display side ...

and to my surprise MacBook started right away fully working not restarting ... BUT there is no backlight ...

I've replaced UP800 - still the same

I've checked Diode mode readings everywhere I was able to find anything with BKLT in description (everything ok). I've checked all pins JP600 and JP900 if there is any abnormality everything OK.

Only thing left from my point of view is to replace UP710 and UP701 (even if all diode reading are ok) because I really don't know what to check

I also tried to decrease and increase brightness via F1 and F2 and no difference only difference was when I put it all the way down the screen goes off (as on normal working MacBook)

Any idea ? According diode readings I'm comparing it in FlexBV with reading that are available for my board.

[obelix24]

what is the exact name of Backligh power ? is it PPVOUT_LUXE_XW ?

[obelix24]

maybe possible to inject 15V to PPVOUT_LUXE_XW when the MacBook is on to see if the backlight will appear ? (I saw this made Sorin - in Electronics repair school on some laptops)??

[obelix24]

any idea ?

[obelix24]

according to repair wiki (https://logi.wiki/index.php/Backlight_Troubleshooting) if you switch display backlight can be off until lid off and on signals are send ...

I've tried with original lid sensor from screen (but still no backlight - it was turning off as keyboard backlight turned off)

i also tried 2 other LID sensors (original one from original screen, new i also tried to program it with nerd.tool1 but still no backlight)

i tried to put board back to original case and still the same issue when screen (all cables are connected there is no backlight and only apple logo bootloop)

so from this i guess there is not problem with LCD but on the board itself ... but where ?

[obelix24]

I've checked more arround UP800 and i noticed that on RP830 (pins LUXE_LG2 and LUXE_LG2_R) i'm getting 0V ...
but on RP833 (LUXE_UG2 and LUXE_UG2_R) i'm getting 5V

RP830 is connected to QP803 - i tried to replace it but nothing and diode readings are ok

also on PPVOUT_LUXE_XW i'm getting 0V (when screen is connected)

[obelix24]

i'm trying to get to understand schematics for this board (and also overal) As i don't have any voltage on LUXE_LG2 and LUXE_LG2_R does the voltange goes in that way i draw ? So from my basic understanding only things that can be wrong are the 2 (or at least one) mosfet QP803 or QP801 or UP800 (but i don't think this is the problem as i've replaced it 3x and still the same result (i'm using donor boards). Or is there anything alse that can cause there is 0V on LUXE_LG2 and LUXE_LG2_R ????

also if i understand PPVOUT_LUXE_XW is voltage for backlight and it should have 15V and this 15V should be generated by QP801 and QP803 am i correct ?