A1990 820-01827

[ipetro]

the board starts at 20v\0.780a and then drops to 0.289a and freezes.

when examining the board I found that the c6700 literally exploded!

I checked PP5V_G3S=21 ohm (should be kilo-ohms), there is no short circuit!
there is no circuit for this board, so I use 820-01041, which complicates the identification of chips.

under the thermal imager the only thing is that the unknown chip heats up a little, when it is removed the resistance on the PP5V_G3S=21 ohm line remains unchanged 21 ohm.
need help from professionals

 

[2informaticos]

Only using IR camera can find the culprit, injecting 5V into 5V_G3S power rail.
You can go up to 5.5V safely.

 

[ipetro]

That's exactly what I did, I applied 1 volt and raised it to 5 volts and only one element barely heated up, the one in the photo (I don't know what kind of microcircuit it is). The 5V_G3S line consumes 0.17 A when applying 5.5 volts

 

[2informaticos]

https://es.aliexpress.com/item/1005006330806484.html

 

[ipetro]

I removed both ISL95870H on this line and I still have 11 ohm resistance on 5V_G3S

 

[2informaticos]

Check any other chip connected to 5V_G3S.
There are also some 10uF capacitors near each chip.

 

[ipetro]

after replacing U8110, U3500, UB700, the 5V_G3S resistance dropped to 0.766 com. the MacBook turns on and charges! the touchbar, keyboard backlight, etc. work, but there is no picture on either the external or internal display (I put the board in another case with a tested display, nothing changed)

 

[2informaticos]

Check diode mode readings at pins 1 & 3 of J8500.

Did you test external video with internal LCD diconnected?