M1 A2338 screen and touchbar issues after cleaning up liquid damage

[mon2]

Ok here. No issue.

Review battery mosfet Q5265 next. No power to the board; meter in resistance mode.

Measure the resistance across:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement in ohms.

[jkruns]

Q5265
Source to drain: 1.8MOhm
Source to gate: 3.9MOhm
Gate to drain: 5.8MOhm

The other boards are in the same ballpark.

Q5270
Source to gate: ~360KOhm
Gate to drain: 2.25MOhm
Source to drain: 2.04MOhm

I also checked Q5230 and Q5240. Both seem fine, resistance gates to drains is consistently in the MOhms range.

[mon2]

Resistance in the K ohms are suspects.

Q5270
Source to gate: ~360KOhm

Flux and remove this mosfet and confirm this measurement again while the mosfet is on your work table and not influenced by the logic board. This mosfet may be defective.

[jkruns]

I'd love to practice my hot air skills, but the resistance across source & gate are exactly the same on the other 3 boards.
This suggests the K Ohm value is ok, do you agree?

[jkruns]

Two more observations.

• PPBUS_AON is a touch on the low side (12.02). OBD says 12.4 but on other boards I've seen 12.95V. Maybe nothing.
• I've read several posts from people who've either installed a new battery or depleted their existing battery over a long time, whose macbooks show the same symptoms. Could it be that the issue is not with the board itself but rather these boards really don't like deeply discharged batteries?

[jkruns]

Here's what the OS registers about the battery and charging.
Other than "IsCharging" = No I don't know what to make of this.

[mon2]

Good report and confirms the battery is detected but concerned about the battery temperature that is sensed.

Can you run the same test on a known good box and post the logs?

[jkruns]

Here's the output of the test on a known good box.

[mon2]

Transfer the keyboard + trackpad from the other known good unit onto this logic board. You also are facing keyboard issues and there are sensors inside of the trackpad.

[jkruns]

Transfer the keyboard + trackpad from the other known good unit onto this logic board. You also are facing keyboard issues and there are sensors inside of the trackpad.

These issues had already gone away. The only remaining problem is the battery not charging when plugged in or booting from battery only. I'm testing this board with the paired touch id sensor transplanted into a chassis with all 100% tested and working components (display, sound, touch bar, battery, touch pad).

It may be worth mentioning I'm testing this with the board not fully tightened down with all the screws and also without the bottom cover (I do connect all the flex cables every single time I test though). I'm assuming the missing bottom cover will not mess up my test results, is that correct?

[mon2]

Do you have normal fan spin or is it still a higher than normal fan spin?

[jkruns]

Do you have normal fan spin or is it still a higher than normal fan spin?

It's barely audible, so I'd call it normal fan spin.

[jkruns]

As it turns out the battery was bad. The other three batteries are fine, but they didn't work because I missed a crucial bit of information: the large T5 screw that holds down the board onto the battery pcb does more than connect to ground like I assumed. I tested the other batteries without this screw in place, primarily because I removed the batteries from their chassis.

It's still a mystery to me why the battery failed. My working theory is some component on the battery pcb broke. So far I haven't been able to tell the difference between a working battery and the dead one with regards to voltage drop to ground in diode mode, or resistance. That said, some parts are covered in glue.

Thanks again mon2, for helping me figure this out. It was well worth the effort to learn new skills.