820-00840-A/A1708 No image, no BL, no boot, no caps lock

recycle66

New member
Hello to all! I am a new member and this is my first post!
I have a A1708 in for liquid damage.
Corrosion near BL circuit small spec on a cd3215.

Changed both CD3215s and now have 20V 0.49A 384-390 mAh. mAh seem to be raising from 384-39and so on very slowly as I write this.
Caps lock doesn’t work, fan spins for less than a minute then shuts off. CPU gets warm/hot.

I have 13V on ppbhsg3h.
mAh is now 401..

CPUVR_SW1 is 0.947V
CPUVR_SW2 is 0948V
PPVCCCPU_S0G_PH1 is 0.942V PH2 is 0.943V
device is now at 20.1V 0.53A and 429 mAh, CPU is pretty hot.

I’m not sure where to go from here any help is appreciated thank you.
 

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

0.9V at CPU core means the board is on but doesn't boot; it drops to 0.6V when does it.
There should be something more affected by liquid.
Check the USB-C redriver chip, on the opposite side of CD3215 chips.
It doesn't appear on the available schematic/boardview.

Be aware, leakage from backlight output voltage to some data lines could damaged the CPU.
Do you get PLT_RESET_L?
 

recycle66

New member
First of all, welcome to the forum!

0.9V at CPU core means the board is on but doesn't boot; it drops to 0.6V when does it.
There should be something more affected by liquid.
Check the USB-C redriver chip, on the opposite side of CD3215 chips.
It doesn't appear on the available schematic/boardview.

Be aware, leakage from backlight output voltage to some data lines could damaged the CPU.
Do you get PLT_RESET_L?

thank you for the welcoming !

the USB-C redriver seems suspect but since it was brushed by a prior shop it’s very hard to tell.. PLT_RST_L is 3.3V, diode reading 0.369.
 

2informaticos

Administrator
Staff member
Redriver chip has any sign of burnt?
You should remove it, if suspect.

BTW, do not quote an entire post visible few centimeters above.
Please, maintain forum aesthetic...
 

recycle66

New member
No signs of burnt.

not sure what else to check on this one besides thing it’s the CPU

sorry didn’t realize I could just reply
 

2informaticos

Administrator
Staff member
You can try known good BIOS, just in case.
But I suspect something more damaged by liquid.
Maybe corroded traces, or resistors.
Is also possible to have accumulated crap under some BGA chips.
 
Top