820-00138 - Not Turning On

[mccafe]

Hello,

I receive a MacBook Pro that does not want to turn on. I found there was a shorted U7310 (unsure if CPU is fried already). Replaced, fan spin and was ready to put together to test, but no longer getting a fan spin after unplugging and replugging charger. Checked ALL_SYS_PWRGD not present. Removed PWRGD resistors one by one and finally Q8150 which brought ALL_SYS_PWRGD back. Fan spins again, however there is 0 volts CPU vcore on all coils. I tried replacing U7200, no go. Measurements I think are pointing back to U7200, but is there anything else I should check?

Any advice? Thanks!

 

[2informaticos]

Q8150 is a redundant protection; you can leave it out.
However, be sure 3V3/5V_S0 and 1V35_S3 are all present.

"I tried replacing U7200"
Any reason to do that?

I bet for dead CPU, because of overvoltage cuased by U7310.
Just in case, compare diode mode to ground at L7310/20/30 with a good board.

 

[mccafe]

Alright, I kept Q8105 off. 3V3/5V_S0 and 1V35_S3 all present.

I replaced U7200 again and CPU Vcore all 3 coils went between 1.2 to 1.6 volts, fan spin for a good 5-10 seconds and then went dead again. Replugging the power and it did the same thing. Did it a 3rd, 4th, 5th time, etc and now it's just dead 0 volts - no fan spin. Intermittent issue where if I keep it unplugged for longer then plugging it back in allows the fan to spin and a pulse on vcore. Perhaps U7200 is bad or this is consistent with a fried CPU. I don't have a good board to test it against.

I have more U7200's coming in and will try replacing all 3 mosfets too since I replaced only 1 (is that a good idea?).

There are some PGOOD signals I want to check, but the board view I have is not exact making it pretty difficult to troubleshoot some parts of the board.