MOTHERBOARD REPAIR ATTEMPT

[Bazel]

Failed attempt to fix faulty MacBook Pro motherboard.
There is a constant power cycle 0V->5V->19V.
The following was noted and the actions taken:
* There was a short circuit on line PP1V85_S2_IPD so components ut101 and ut102 were replaced. This fix solved the short problem.
* When the power cycle reaches 19V, there is a short on PPVBAT_AON_CHGR_REG for a second and the power falls back to 0V and cycles again.
* PP5V_S2_MAIN also shorts to ground during the power cycle (multimeter short test shows that a short circuit comes and goes). U5700 was replaced but the issue persists.
* Q5420 was also replaced.

The attached video shows the power cycle sequence.

 

[2informaticos]

I'm not sure if I correctly understood, please clarify.
Do you check in diode mode (or ohm scale) with power applied on the board???

Also tell us the motherboard code.

 

[Bazel]

diode mode
820-02100

 

[2informaticos]

"diode mode"
Do NOT do that ever again!!!

Remove both F5200/1 and check if C5250 voltage is stable.

 

[Bazel]

Ok thanks for advice
when F5200/1 removed, reading on
C5250 is 12.36v

 

[2informaticos]

So your problem is on PPBUS_AON side; resolder the fuses.
Check diode mode to ground at 3V8_AON and PPBUS_AON.

I supposed you've got stable voltage at C5250.

 

[Bazel]

So your problem is on PPBUS_AON side; resolder the fuses.
Check diode mode to ground at 3V8_AON and PPBUS_AON.

I supposed you've got stable voltage at C5250.

Yes stable 12.36v on c5250
No short on PP3V8_AON
No short on PPBUS_AON either

 

[2informaticos]

Check diode mode on all other secondary power rails; like 3V3/5V_S2, etc...
Also check at U8100 and U7700 LDOs; pages 41 & 37.

BTW, any reason to quote an entire post, visible few centimeters above?
Please maintain forum aesthetic...