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820-00923-A not turning on - 20V 180mA on the charger

F

Fanfwe

Member
Hi,
I have this board from an A1706 which is not turning on.
I do get 20V from the charger.
Checking power rails and big coils on the board, I can see that I'm not getting PP5V_S4_T_USBC and PP5V_S4_X_USBC (enable signal is driven low by CD3215s)
Also PPVCCEDRAM_S0_CPU is not present (created from PPVCCIO_S0_CPU which is present, but enable signal coming from CPU CPU_ZVM_L is low).
And obviously, missing VCore: PPVCC_S0_CPU and PPVCCGT_S0_CPU are not present.

No sign of liquid. CPU gets warm but not hot.
 
2informaticos

2informaticos

Administrator
Staff member
Mentioned 5V_S4 are only used to power external USB-C device.
Of course, no voltage if no device connected.

Any history available?
Did you try known good working BIOS?
 
F

Fanfwe

Member
There's not much to say about history. This is in fact a laptop that comes from a friend of mine. It stopped working a while back, and he just stopped using it and got a new one. He eventually gave it to me so I could take a look, just in case I could revive it.
He said it just stopped working one day, it wouldn't turn on anymore.
He also said that it was possible that there could have been a bit of liquid spill at some point, but wasn't too sure.
And after taking the board out of the case, I don't think there was any liquid ingress, the board looks perfectly clean after inspection under microscope. No sign of liquid or corrosion anywhere.

I have not tried messing with the BIOS yet, but this was indeed on the top of my list after I did the first analysis I posted up there. But I wanted to get some other opinion first. So you think I should try reflashing a clean BIOS ?
 
F

Fanfwe

Member
So, I have borrowed a SPI ROM from another board that works. I know ME region is not compatible and so on, but I think it shouldn't matter and I should at least be able to boot with it.
But it didn't work, still stuck at 180mA 20V, except that I noticed something which I didn't pay attention to before. It does a few boot loops 180mA, back to about 20mA and then tries again, 180mA, and so on a few times, until it stays at 180mA.
 
F

Fanfwe

Member
Yes of course. All the measurements above were done with the board alone. The test with the ROM swap also.
 
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