Macbook pro a1989 - 20v not turning on

[obelix24]

I just got Macbook Pro a1989 that when connected to charger is getting 20V and up to 1,3A (when battery is connected) 0,8A when battery is not connected.

but after few seconds it jumps to 0A and restarts (No chime, no picture)

every port is taking 20V so all CDxxxx should be ok.

there was corrosion on LCD connected (enough to clean no pin is burned) - so i cleaned it and it looks ok.

I've checked under termal camera and there are 2 hotposts on U7800 (but this chip looks spotless) i've checked all
L7821,22,20,19
L7817,16,14,15
L7809,08,07,06

all diode values (according to FlexBV looks ok)

hotspots are in the corner where pin 1 is located and then on opposite side around pins 90-180

is this normal behaviour ? or it is possible that U7800 is faulty ?

[mon2]

Sounds faulty. At least remove and check under the device to see if there are any issues.

[obelix24]

ok I've replaced this U7800 and not MacBook stays on it draws healthy 20V and charge battery.
but there is still no chime or display.

I've connected it to another MacBook and revived, restored via Apple Configurator 2 (successfully finished)

but still no chime or anything on the screen.

I'm able to put MacBook to DFU mode and execute restore but nothing on screen, Touch Bar, CAPSLOCK light is also not working

but trackpad is clicking so this means T2 is ok ... also Revive was finished so BridgeOS should be also ok.

I'm using know good screen + keyboard.

I've tried to connect this MacBook via HDMI to TV to see if there is any output and nothing (I've tried with internal screen connected and also disconnected (no difference still no output)

Any idea what to do next ?

[mon2]

What is the current draw? Do you see power cycling on the USB C meter?

[obelix24]

With battery connected it climbs to arround 20v 2,5A a stays around
with battery disconnected it goes to 20v 0,6A

it's stable no cycling

[mon2]

What is the voltage to ground of PPBUS_G3H?

[obelix24]

With battery disconnected i got stable 12,65V on PPBUS_G3H - on USB-C meter i get 20V 0,6A
When battery is connected it slowly rises from arround 11,4V to 12,46V (here it stays) - on USB-C meter i get 20V 2,63A

[mon2]

Test the smbus voltage on the battery pack with the adapter connected.

Review the current sense resistor path at the input to the isl controller that creates ppbus_g3h.

[obelix24]

both SMBUS_3V3_BAT_SDA and SCL i'm getting 3,3V

i've removed CPU heatsink and checked with thermal camera (compared to working icloud locked board) and i have one hotspot approx in the middle of the CPU

I've checked EDP_INT_AUX_P and it looks ok - Diode mode 0,2

[p0cas]

I have the same problem you find a solution ?

[obelix24]

No i haven’t i’ve used T2 from that board to another icloud locked to make it usable again.