Macbook A2337 Not turning on

[Instafixx]

Device came in for screen replacement. We check the OEM screen and installed it on this device and every thing was fine.
Now the device will not turn on and pulls 5V with very low amps.
Sometimes it goes up to 20 V with zero amps.

Ppbus is 12.2

Device not in dfu.
Pp3v8 vddmain is present

Pp5v_s2 absent with no shorts.

Thermal inspection show U7700 heating up at on point.

 

[2informaticos]

Tested without LCD assembly?

 

[Instafixx]

Above readings are with board on a desk

 

[2informaticos]

What about U8100 and U7700 LDOs?

 

[Instafixx]

Upon further checking
PP5v_s2 is missing
P5Vs2_EN is also missing with no shorts.
PPBUS_P5VS2_VIN is consistent with PPBUS_AON

PP3V3_S2_UPC is present.

For a very brief time I found one c port making the amp meter reboot

 

[Instafixx]

Followed the slight heating at one corner of U7700 and found that PP0V805_S1_VDD_FIXED is shorted with diode reading of 0.004.
As per opneboard data the reading should be 0.240.

Should we inject 0.5V and see ?

 

[Instafixx]

Please guide

 

[2informaticos]

You can go up to 1V.
Anyway, yo will need a good thermal camera to find the culprit.

 

[Instafixx]

Tried that. Nothing got hot.
Removed all the caps and resistors of this line .
Still the short is there.

Bad M1 chip ?

 

[2informaticos]

You can't get anything really hot.
Just look on IR camera where is the higher temperature.
Remove CPU heatsink first.

 

[Instafixx]

There is no place where there is high temperature . Heat sink is off.
Moreover all the caps and resistors of this line is off the board now. still a short exists.

 

[2informaticos]

Very likely CPU problem...