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820-01987 all power rails but no boot

J

jadao

Member
Got this liquid damage board. I have 20V on usb-c meter.

With battery I get 20V 2A so it seems charging well, the fan spins also with and without charging cable. Without battery I get 20V 0.55A.

Board reacts to power button, opening the lid, pressing the trackpad or a keyboard key. I can see the fan stopping with 0A on the usb-c meter. an it goes back to 20V 0.55 when I press again the power button.

There is no image, no backlight and no boot, tested also hdmi with external monitor and disconnected internal lcd cable.

I have these voltages at the coils:

L7030 : 12,60V

L7690 : 3,3V
L7670 : 5,0V

L8410 : 0,08V (backlight coil)

L8100 : 1,2V PP1V2_S3
L8102 : 0,959V PPVCCIO_S0_CPU

L7702 : 1,035V PPVCCEDRAM_S0_CPU
L7270 : 1,021V PPVCCSA_S0_CPU

L7210 : 0,824V PPVCC_S0_CPU
L7220 : 0,825V PPVCC_S0_CPU

L7410 : 0V PPVCCGT_S0_CPU
L7420 : 0V PPVCCGT_S0_CPU


Tried a DFU revive then restore but nothing changed. SMC bypass also doesn't change anything.

Tried also the board with nothing connected and noticed suprisingly that without the trackpad cable plugged in the board will go to 20V 0,12 ->0,55A then after 3 secondes come back to solid 20V 0A at that time I will only have 3.3V and 5V. If I press the power button it will simply repeat 20V 0,12 ->0,55A for few seconds and come back to 20V 0A.

I don't know at this point what to look or check further...

Thanks
 
J

jadao

Member
Yes it seems I completed the dfu, both revive/restore I had no error but nothing happened on device under dfu.

As for recovery, I don’t see how I could start it, I have no chime, I don’t see anything on internal lcd or external monitor, No capslock or usb mouse light, same with usb keyboard.
 
2informaticos

2informaticos

Administrator
Staff member
Restore option in DFU should continue with macOS fresh installation, as internal SSD is erased.

T2 machine remains in off state, once DFU completed?
 
J

jadao

Member
Yes exactly, that's what I noticed on machines where a dfu restore solved the problem.

And yes this T2 machine remains in off state once dfu is completed, I don't see the apple Logo that bring you to the question mark or any process to install a fresh OS...

I am not sure if it's normal on this machine the trackpad cable trick...seems odd to me that if I disconnect it the machine stays at 20V 0A.
 
Last edited:
J

jadao

Member
Areas affected by liquid:
ISL9240 had some greeny crap corrosion, U3710 WLAN serial EEPROM, J6410 (speaker).

I have just discovered 2 test points TP5905/06 completely gone ISNS_HS_OTHER3V3_P (and /N) but it seems there is no U5440 on this board...
I will look again carefully and do an ultrasonic.
Thanks
 
J

jadao

Member
After an ultrasonic I don’t have anymore 20V, I have 5V 0.16-0.20A and loops on both ports usb-c meter.

I still get 12.25V on PPBUS_G3H, 3.3V on PP3V_G3H and 5V on L7030.
No more PP5V_G3S...
It doesn’t enter DFU mode anymore.

Checked around both usbc mux chip and didn’t find any short on signals or power rails…Surprisingly, no matter witch usbc port is plugged in, I will find 5V on both usbc mux associated fuses.(2020 boards?)

Something should be wrong under bga as the ultrasonic changed the state of the board.

I found them difficil these recent boards, specially with the sensistive cpu, easy to loose confidence?
 
2informaticos

2informaticos

Administrator
Staff member
Looks like T2 doesn't work; not properly at least.
Do you get all AWAKE and SLPS2R voltages?

"find 5V on both usbc mux associated fuses"
As per schematic, both fuses are connected together.

If you didn't use sweep function, ultrasonic clean could damaged the board; read about ultrasonic hot spots.
Check now for knocked off components, or broken traces.
 
J

jadao

Member
Hello 2informaticos,

Sweep function is embedded by default in my ultrasonic cleaners. I have no way to use them without sweep function.
I think I have a good idea about cavities, transducers, dead or hot spots and standing waves.

This board didn't have the acid very agressive damage that we are used to see from time to time, not the kind of damaged board where components come off alone. After ultrasonic, the board is in pristine state not the greyed discolored components from over ultrasoniced board.

Unfortunately I had to return the laptop, If I had time, I would have check the SLPS2R and AWAKe voltages and probably reflow slightly the T2...

Thanks as always.
 
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