A2442 820-02098 after liquid damage, for data revovery

[adrko]

A2442 02098
Liquid damage, data recovery is a priority
Lots of damage everywhere, I replaced and reworked 70-80% of stuff that I thought is critical

When I start diagnostics - 5V 0amp on cable, out of the chasis
After PMIC U8100 replacement I'm getting 5V 0.25-0.3 amp
Nothing is getting warm, I didn't discover any shorts

Whats giving me a head ache is the U8100
Pulled it from my own 100% working A2442
So:
- logiwiki says it should turn on bucks if PMU_VDDHI ~4.7
I was getting 3.2 ish
- outputs of U8100 are unstable
- schematics says both resistors there should be 200k
- one resistor(R8170) from the damaged board was corroded, so I assume it's out of spec(?)
- To limit potential errors I pull both from previously mentioned known good board
- I check both of them, one is 290k, other is 1.07M

Schematics says both 200k

I check with online voltage divider calcs, 2 different combinations of this give either 10V or 2.6V
Is it my lack of knowledge or the information is wrong somewhere?
When I removed both, on cable 5V, 0amps of course - so perhaps I looking at the right place?

But I need help - I'm not able to fully understand how the U8100 works.
And if I'm missing power on signal or something like that?


PP1V8_S2 unstable 0-1.8
PP5V_S2_MAIN unstable 5.2-0
PP1V2_AON stable 1.199-1.2
PP1V2_S2 unstable 0-1.2
P5VS2_TPS_PWR_EN unstable, on/off - from what I understand this is turning on UC260 which produces PP5VS2_MAIN
PP3v8_AON 3.8 stable
PPDCIN_AON 5.155-5.148
PPBUS_AON 12.30-12.29

 

[2informaticos]

"I check both of them, one is 290k, other is 1.07M"
Do you mean resistors removed from working board?

If R8170/1 are equal, then PMU_VDDHI must be half of PPBUS_AON.
Considering R8170=1.07M (1-1.2M possibly) and R8171=290K (possibly 300K), then PMU_VDDHI will be around 2.5V aprox.
This make sense also, as this signal triggers MPMU around 1.5-1.6V (mentioned in schematic).
Stable PPBUS_AON (12.3V) should never trigger this MPMU input.

Before going to PMU bucks, you should get stable LDOs from both PMUs.
Probably PMUs detect some problem on secondary power supplies.

Heavy water damage boards are nightmare.
You can expect bad CPU; in case its power supplies have been affected.
Is the machine recognized into DFU?
PMUs LDOs should be stable, if you can eneter DFU.

 

[adrko]

Thank you for your reply. Yes - resistors measured when completely pulled from motherboard, removed from motherboard that was 100% working during daily use past 6-7 months. I tested them with two different multi meters.

Oh, I see now - it is clearly mentioned on the same page in the schematics, thank you for pointing that out. My measurements make sense now.
I put the resitors back, 12.3V PPBUS_AON and 3.089V PMU_VDDHI.

U8100 LDO:
VIN_LDO - PP3V8_AON_MPMU_ISNS - 3.8V stable
PP3V3_S2 - 1.4 - 1.7 - 3.29V - cycling
PP1V8_S2SW_CLVR_VDDC1_LDO - 0.7 - 0.8 - 1.8V - cycling
PP3V3_AON - 3.29V - stable
PP0V8_S2_CLVR_VDDDIG - 0.34 - 0.60 - 0.79V - cycling
(90% sure this one was shorted with 3V8, corrosion and liquid was there)

PP1V8_AON - 1.8V stable
PP1V2_AON - 1.19 - 1.20V
PP1V5_AON_VCORE_MPMU - 1.49V - stable

U770 LDO:
PP1V2_S2 - 0.7 - 1.22V - cycling
PP1V8_S2 - 0.8 - 1.79V - cycling
PP3V8_AON_SPMU_ISNS - 3.79V - stable
PP0V72_S2_VDDLOW - 0.5 - 0.74V - cycling
PP1V2_AWAKESW_BLC - 0V - in diode mode - 0.400V and rising
PP1V8_AON_SPMU - 1.79V - stable
PP1V2_AON_SPMU - 1.2V - stable
PP1V5_AON_VCORE_SPMU - 1.49V - stable


It was not detected with dfu, but I used finder built in tool, not apple configurator.

Can you please tell me what U8432 is responsible for?
PP1V8_AON - 1.8V stable
P5VS2_PWR_EN - 0.6-0.8-1.8V - cycling
P5VS2TPS_PWR_EN - 0V
IPD_PWR_EN_PMU - 0V
IPD_PWR_HOLD - 0V

 

[adrko]

Forgot to mention - U5200 and UP800 were seriously corroded all around, I replaced UP800 with one from donor, but U5200 I just reballed, because I did not have anything to pull from. Didn't want to touch working motherboard just yet at that point.

 

[2informaticos]

U5200 is good now, if you get stable 3V8_AON.
The advanced corrosion could caused voltage spikes on the outputs; CPU may be damaged actually.

"PP0V8_S2_CLVR_VDDDIG - 0.34 - 0.60 - 0.79V - cycling
(90% sure this one was shorted with 3V8, corrosion and liquid was there)"
Bad news also; almost 500% overvoltage...

 

[adrko]

Hello

Thank you for the help, that's an okay news for me. To be honest I am glad I can stop working on it.

A bit off topic - would you be so kind and point me in the right direction?
I want to have better understanding of how laptop/consumer electronics work, and to be able to understand schematics better.

I really struggled with understanding how anything worked on this particular mac.

Google would be best probably but I feel like I'll have to go through lots of worthless websites to find anything meaningful.

Thank you and have a pleasant day

 

[2informaticos]

The forum goal is to help in process repair.

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