820-01598 not detecting or running on battery after liquid ingress.

joshAU

Member
Hi all.

I'm working on a 820-01598 that had water damage.
It originally came in not turning on.

The only signs of corrosion was on the bottom side of the board.
There was a small amount of corrosion on the battery PCB,
On the logic board, there was a small amount of corrosion near F7000.

I'll attach an image of the logic board.
The other areas that had corrosion do not seem to be related to the battery charging.

I cleaned off the logic board and battery PCB and tested it.
The unit powered on and booted OK, however the battery reported 1% and failed to charge at all.
If I disconnected the USBC, it would immediately turn off.

I shut it down, and tested with a new battery.
The unit powered on and was charging the battery - the charge increased from 70-80% while charging.
The System information correctly detected the battery, and said the new battery had a charge count of zero.

I left the job on the bench last Friday.
This morning I again powered it on, and it doesn't detect the battery at all.

I tried PRAM/SMC reset.
I re-seated the battery.
I tried with another new battery.
None of the new batteries detect, charge, or will run on the battery alone.

I tested with USBC connected, with the customers genuine 3A charger, and a workshop 4A charger as well.

F7000 is not shorted, reads 12.61v with USBC connected.
On the battery BMU Flex Solder Pads, PPVBAT_G3H_CONN also reads 12.61v.

I don't think it is related, but near F7000, a zero ohm resistor, R6700, reads open resistance.
It measures 12.61v on pin1, PPBUS_G3H and 0v on Pin2, PPVIN_S4_TPAD_FUSE.
The location on the board for F6700, the TPAD Fuse, is not populated.

I'm not sure where to start diagnosing this.
I've had little experience with batteries in these units, usually once I can get them working they've charged and worked on battery fine.

Any help greatly appreciated.
 

Attachments

  • 820-01598-3.jpg
    820-01598-3.jpg
    644.4 KB · Views: 0

2informaticos

Administrator
Staff member
R6700 is not battery related.
You must resolder it anyway; PPBUS_G3H is needed by the trackpad actuator.

First check SYS_DETECT and SYS_DETECT_L signals.
Wrong values may be caused by corroded R6956, or Q6955.

D6950 is another suspect.
Check diode mode on SCL/SDA lines before and after Q6950.
 

joshAU

Member
Hi 2informaticos.
Long time no speak. :)
Thanks for your suggestions.

SYS_DETECT 3.29v
SYS_DETECT_L 0v

R6956 is 10K ohm. 3.29v on both pins.
Q6955 0v on pin3 (SYS_DETECT_L)
Q6950:
Pin1 1.8v
Pin2 1.8v
Pin3 3.3v
Pin4 1.8v
Pin5 1.8v
Pin6 Fluctuates slightly between 3.24v and 3.29v

Diode mode, red to ground:
Pin1 428
Pin2 -721 (beeps)
Pin3 431
Pin4 428
Pin5 -722 (beeps)
Pin6 431
 
Top