820-02020 Liquid damage - short on PPBUS_AON.

it-solve

Member
Just got this in today with liquid damage. When connected to the charger with a battery it gets 5V 0.33A and the Apple chips get very hot. Noticed it has a short on PPBUS_AON with removed F5200.

Seems like will have to buy FlexBV to be able to go through the board view. Where shall I start? Is it worth it, considering apple chips are getting hot?

Thanks
 

it-solve

Member
Only the three coils (3.8V power supply) next to the Apple chip seems to be 33Ohm with removed Fuse
1631786577193.png

Lifted them and seems all three are connected to one spot on the Apple chip side. And the short is on that side. PPBUS_AON short is gone once they are lifted up
 
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it-solve

Member
If you are referring to the MOSFETs between those three coils and the caps in the picture above. They do not seem short. The left side of the coils towards the apple chip, are joined together and is 33Ohms. PP3V8_AON side I believe

Seems like I need to get the board view, but either way no donor board for these MOSFETs.
 

2informaticos

Administrator
Staff member
I cannot see too much in that small picture.
If you get 0 ohm between PPBUS_AON and these coils, then one of mentioned chips is shorted.
These chips must have a marking code, which identify them as dual N-channel MOSFET.
 

it-solve

Member
For some reason, i could not post a bigger picture.
I've lift them up at X places and short is here
1631793408910.png

Seems like VDD of U7700. Perhaps busted u7700? Is that the Apple chip?
 
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2informaticos

Administrator
Staff member
33 ohm to ground could be correct value on 3V8_AON, but not on PPBUS_AON.
I said to check for pure short BETWEEN PPBUS_AON and 3V8_AON, not to ground!
Such short may only be induced by one of Q5800/20/40.
 

it-solve

Member
You were right the one in the middle is shorted. Any suggestion what donor board I can have this mosfet on? I have A1990 and A1706 boards from never gen macs. Do you have an idea of the specs of the mosfet. AONE36196, DA37EK search didn't bring much?

IT-Solve_Repair_21-09-17_06-11-40.jpg
 

it-solve

Member
Got the mosfets today. Slightly different markings 36196 .
Replaced the shorted one in the middle and still stuck on 5V 0.15A

Seems like the 3.8V controller is heating up to 38*C at room temp 20*C. Cant measure any other shorts
 

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2informaticos

Administrator
Staff member
Do you get correct PPBUS_AON now?

One of the chips powered from 3V8_AON can be damaged by overvoltage through the burnt MOSFET; possibly U7700, or U8100.
U5700 is also suspect.
 
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