A2159 dead, no known damage

[Fyod]

Hi all,
I'm looking at buying and fixing an A2159 for myself.
Seller says his son brought him the laptop saying it just suddenly turned off. Pretty sure they tried charging/booting.
No mention/sign of liquid damage or drop.
Are there any known issues on these models like sudden CPU death?
I know it's just wild guessing, but I would like to have some idea of what to expect before diving in.
Cheers!

[mon2]

Re: A2159 dead, no known damage

The new models are based on very small (cell phone) style of parts. Like all repairs, it is a gamble. Do you have the tools like a multimeter & soldering tools (hot air + standard soldering iron) + flux, etc. ? It will be a learning experience but may result in a non-working unit. If you are ok with the risks then proceed.

Source a USB Type C Power meter so that you can review the current & voltage draw from the external power adapter. Start from there.

[Fyod]

Re: A2159 dead, no known damage

Yes, I have all the tools needed and have done laptop repair in the past.
I have found the BV and schematics for the model as well.
My question is mainly in regards to the CPU, because I know that models like the 12" Retina just suddenly die irreparably.
Guess I'll try.

[Fyod]

Re: A2159 dead, no known damage

So I got the laptop. Seller either didn't know or lied, either way there was corrosion from liquid on about 5 spots. Seems like water as there was no gunk or sugar.
On first try, the input (original 96W charger) read 5V, 0.4A.
After a thorough ultrasonic clean and dry, I get 20V and jumping current between 0.04-0.09A. So at least I got PD negotiation back.
I have gone over the board under the microscope and I do not see any obviously damaged/burned parts.
There was only a smoke trail on the thunderbolt connector itself, looks like a short from 20V (pin 57) to gnd (pin 1), possibly the charger took the hit.
I have not found any blown fuses.

Here are the bus voltages based on other threads:
PPBUS_G3H 12.26V
PPDCIN_G3H 20.30V
PP20V_USBC_XA_VBUS 20.30V (depending on which is connected)
PP20V_USBC_XB_VBUS 20.30V ^
PP3V3_G3H_RTC 3.3V
PP3V3_G3H 3.3V
PP5V_G3S 0.02V jumps to 5V every 3 seconds or so, 21kOhm to gnd

What should I look for next?

[mon2]

Re: A2159 dead, no known damage

Pins 7 & 8 of U7650 are responsible to measure the current of the PP5V_G3S rail. Confirm the voltage readings for each leg. Specifically, need to be sure that R7672 is present.

Without power, measure the resistance of R7672 to confirm it is 4k42 (according to the schematics).

If either of these legs is broken due to corrosion, then the U7650 regulator will enter chirp mode if it believes to much current is being drawn by this rail.

[Fyod]

Re: A2159 dead, no known damage

R7672 0.945k
P5VG3S_CSP1 (pin 7) pulsing 5V, pin 8 same
No corrosion, both look ok.

Edit: R7673 is 0.945k as well,

[mon2]

Re: A2159 dead, no known damage

The resistor readings are not correct for either resistor.

Recommend to carefully remove each out of circuit and measure them again. These are 1% tolerance so should be close to the schematic values. The lower values may be throwing off this regulator.

Respectively consider to replace with fresh 0201 1% parts.

[Fyod]

Re: A2159 dead, no known damage

I'm still looking around the board for a short (so far unsuccessfully) before I replace the resistors.
Is 3.4Ohm to ground normal for CPU rails?

[Fyod]

Re: A2159 dead, no known damage

I have noticed that PPBUS_G3H dips from 12.36V to about 12.24V, PP3V3_G3H dips from 3.3V to 2.6V at about the same interval as PP5V_G3S jumps to 5V.

There has got to be a short somewhere when PP5V_G3S is supposed to turn on, just can't find it.

[Fyod]

Re: A2159 dead, no known damage

After installing the board back into the chassis (incl. connected battery) the input goes from 5V to 20V 0.4A to 20V 1.2A to 20V 2.2A to 20V 0A.

The moment it hits ~40W, U3200 gets very hot.
With thermal paper, i can determine that the upper left side of the chip is where it is hot. This is where all of the connections to PPDCIN_XB_G3H_F are.
Same situation on the second USB port, but I do not know if the second chip gets hot as well, as it is currently on the underside.

What do these chips have in common that could be shorted?
PPDCIN_XB_G3H_F does not seem shorted (100kOhm).

[mon2]

Re: A2159 dead, no known damage

U3200 should not be as hot as you are observing unless something is wrong with this component.

Remove all power. Meter in resistance mode.

Check the resistance to ground of fuse F3001, pin # 1 & # 2. (you just updated this value so ignore)

You can consider to desolder the fuse @ F3001 and this should remove U3200 from the equation (by removing the flow of PPDCIN_G3H to this ACE controller).

Respectively, U3200 cannot be used to power the logic board but you can use the other ACE controller.

It appears that U3200 will need to be replaced.