A2442 820-02098 Heavy liquid Damage and short on PPBUS_AON

[it-solve]

Bit shooting in the dark here without schematic and boardview.

I can detect shorts in the PPBUS_AON fuses.
I pushed 2V through the shorted PPBUS_AON line but did not pull any current. Perhaps too low voltage to trigger any short. Anything to consider before I ramp up the injected voltage to detect a short location?

Also, shall I UC the board as it is very sticky after the energy drink spillage and seems heavy oxidation around the SSD, audio amplifier chips in particular?

Lift up the F5200/01 fuses, and it seems short is on the PPBUS_AON side.
PP3V8_AON - 0.156
PP5v_S2_MAIN - 0.397
PP1v8_S1_CLVR_VDDH - 0.101


Not sure what area to concentrate on first.

 

[2informaticos]

What is the exact ohm reaidng for that short?
Compare its value with the big coils readings.
If you don't get similar reading on any coil, then is safe to inject voltage.
Remember to set amp limit to max on your lab PSU first.
If there is pure short, 1-2V should be enough to find the culprit; but you need at least 10A (recommended 20A) PSU.

 

[it-solve]

Fuse Side - 50Ohm. I cannot find the same or lower value on any coils. The closest I get is 120Ohms.
I usually use this little buck converter with a Lithium battery limited to 2V and 2.5A.

I also tried with the 1V and 2V 15A linear bench supply. But not pulling any current. Strange.

PPBUS_AON - ~ 12.00v. Measurable on the 2 fuses at the edge of the board, adjacent to the battery flex marked "12." (See photo below for reference.)

Diode mode reading: 0.430

- https://repair.wiki/w/A2442_2021_14"_MacBook_Pro
is described in Repair Wiki, that should be over 50Ohms right?

 

[2informaticos]

50 ohm doesn't allow you to heat anything with low voltage injected.
Please, read Ohm law and get some basic electronics knowledges also.

2V into 50 ohm generates 40mA; which means 80mW in power disipation (no heat detected).
Not strange at all.

Ohm scale is used for low readings, like under 0.010 in diode mode.
So post diode mode readings, on both ways; red to ground, also black to ground.

Remove F5200/01 and check where the low reading remains.
If is for sure on PPBUS_AON power rail, is safe to inject until 15V, getting 4.5W (for 50 ohm); enough to detect heat on the board.
16V filter caps resist until 18-20V, but is not recommended to stress them too much; let more time the 15V applied eventually.
However, be very sure the low value doesn't come from a secondary power supply; like L5800, L9400/20, etc.

 

[it-solve]

I am aware of the Ohm law, but I haven't thought of how it will apply in this scenario. What first-hand materials would you suggest for basic electronics knowledge?


My 50Ohm on the PPBUS_AON fuses now measures 150Ohm. PPBUS_AON - 0.152 (both ways in diode mode), still lower than TCSR reported at 0.430

I took measurements around the coils, and there are no coils measuring below 0.105 red probe to the ground. Snapped some measurements in this photo both ways red probe to ground (Green Measurements) and black probe to ground (Red measurements)


Red probe to the ground in diode mode
PP3V8_AON coils measure - 0.160
PP5v_S2_MAIN - 0.397
PP1v8_S1_CLVR_VDDH - 0.101

 

[2informaticos]

"I am aware of the Ohm law"
Then you should know that is impossible to adjust voltage and current at same time, when inject voltage (into a fixed resistor).
You can only set a max current over the expected one for a giving voltage; to avoid PSU going into protection mode.
Actual current is decided by the voltage applied; you can't change resistance value on the board.
That's the reason you can't use 2.5A PSU for this purpose.

You should get big difference between diode mode readings on PPBUS_AON.
In reverse way (black on ground) should rise much more.

Check direct resistance (ohm scale) between PPBUS_AON and 3V8_AON.

For basic electronics I recommend to read old electronics papers, available now for download on Internet; like Elektor, Electronica, Tehnium, Radio, etc...

 

[it-solve]

Thanks for the explanation. Much appreciated.
I use this portable buck converted with CV/CC protection, and I usually set/limit it to 2.5A with 2V when injecting, and if nothing heats up, then I start ramping up the current (if CC triggers) or voltage(if line permits). This time it was not pulling any current, hence didn't see the reason for ramping current limitation.

When measured this morning, both ways, it measured at 0.350 at first, then dropped to 0.155

490 Ohms between PPBUS_AON and 3V8_AON
1.2 MOhms between PPVBAT_AON_CHGR_REG and 3V8_AON

 

[2informaticos]

Do you actually get any voltage at PPBUS_AON?
If not, remove the fuses and check C5250 voltage.
If still nothing, check R5220 voltage presence.
Try to detect basic connections of U5200, using 02100 schematic; P_IN, AUX_DET, VDDA/P.

 

[it-solve]

Using the magsafe charger stuck at 5V
PPBUS_AON - 0.169V with fuses on; 12.93V with removed fuses. Seems like U5200 is fine. Shall I lift up all coils and determine where it is reaching?

Particularly audio amplifiers look bad , but no direct short

 

[2informaticos]

If these caps are connected to PPBUS_AON, remove them and clean all area.
Then check again diode mode.

 

[it-solve]

It turned out that the caps on the other side were shorting. PPBUS_AON is stable now. However, that middle amplifier had corroded pads and had to remove it. together with a bunch of filtering caps around it. It seems to be the same amplifier as -02100 SN012776B0YBH



Without it, it turns on now and pulls 20V 0.4 without battery and 2.2A on battery. Works for a minute (with no screen) and shuts off, then turns on by itself. Repeats about five times then shut down to 0.02A draw. Until reconnect the charger to MagSafe, then repeats.

I wonder if this model can fire up without the one amplifier chip, they seem to be 3.

Voltages on big coils seems to be stable, except this one.


Not sure what area this chip covers. I could not locate these markings on 02100


Shall I run it by UC first, as this gunk becomes harder to remove each time I reheat? I am not even sure if the 70*C UC batch can clean it.

 

[2informaticos]

Gently scratch the affected areas, around components; be aware don't knock off components, or damage traces.
Then clean with IPA and toothbrush.
Use ultrasonic cleaning only if you note corrosion under BGA chips.

 

[it-solve]

OK managed to bring it to life, it turns on now, and I can load the system. Though due to the missing amp seems like the sound is not working okay and not getting recognised. Comes up with an error message - "Could not load up sound preferences".

It turned out that the caps on the other side were shorting. PPBUS_AON is stable now. However, that middle amplifier had corroded pads and had to remove it together with a bunch of filtering caps around it. It seems to be the same amplifier as -02100 SN012776B0YBH

Does anyone have an idea where I can get it online? Apart from a donor, 02100 or 02098 boards.

Also, does anyone experience missing audio on these M1s that may cause a video not to play? When I load Youtube/Yahoo videos, it is just stuck on one frame. If I forward it to another frame, it just stays at it without playing it. I erased and reinstalled it to eliminate Software issues. Wonder if Sound related issue may cause it. Magnetic charger models will happily play audio without a sound chip.

 

[2informaticos]

The audio codec must be recognized, even audio amps are missing.
The problem is that these amplifiers are powered from PPBUS_AON.
Such advanced corrosion caused leakage to M1 data lines, directly connected.
I don't see a solution for this case.

You can find the corroded small caps in older MacBook boards for sure.
But changing them don't help.

Do you get audio on HDMI at least?

 

[it-solve]

Yes Audio Amps were nasty, probably still corrosion underneath, haven't UC'd yet. This is how it was when remove dthe middle one




HDMI Audio is working
BT Audio is working

Video start playing now once I get it connected, it keeps playing when disconnected too.

 

[2informaticos]

So you get audio on the speakers now?

"Video start playing now once I get it connected, it keeps playing when disconnected too."
Disconnecting what?

 

[it-solve]

Sorry I wasn't clear. No audio on speakers. Audio plays over HDMI/BT. The video keeps playing with no sound when disconnected HDMI/BT. While before I connected HDMI, it would stay stuck on a frame but show playing.

 

[2informaticos]

I bet for T2 internal damage, caused by leakage from audio amplifiers.

If you still want to use it in laptop mode, get a portable USB speakers.