00281 with extremely hot mosfets

hi, i got this thing back to life by replacing the ISL. Everything checks out, ut upon handling the board i noticed that both QB300 and QB400 get extremely hot (burnt my finger on them). when using the corresponding USBC ports.
I know mosfets can get pretty hot in general, but this is extreme. Could this point to anything? Or should i just go ahead and replace them?
The fets on the other end of the board dont get anywhere near this hot when usbc charger is connected on that end.


Staff member
Compare diode mode readings on test points of corresponding MOSFETs.
Maybe one section is not enabled and internal diode gets really hot in such case...
sorry was in a rush and just replaced them, mosfets are now running at normal temps.
The Mac now boots into the critical update.. before this everything was booting just normally...pfffft
No difference with an external screen, but now it decided to boot to a question mark folder, so the SSD is not seen.. fucking hell, the NANDS are getting all their voltages (3v3, 1v8 1v2 and SSD_CORE 1v0 ) and are getting pretty warm.. what a trolling board.
Gonna check some more and see what the hell is going on.
sorry, should have added that info.

it had liquid damage.
Found some damage to U7000 area, replaced U7000 and this brought back the enable for pp3v3_g3h which was missing.
after that ppbus and 3v3_g3h came up, but board wasnt booting.
Then found corrosion under the 1v8 pad of C8028, which was disconnected from the 1v8 rail.
Ran a jumper to the cap and the board fully worked after that. (it booted into my testdrive and i could see the onboard SSD and browse its files)

i then noticed the burning hot mosfets UB300/400 and decided to replace them.
Afterwards, the board still booted, but this time coming up with the Critical Update thing.
After a couple of tries, the board can't see its own SSD anymore


Staff member
You probably have corrosion on the SSD area too.
Clean Lifeboat connector and be sure to get all SSD voltages.
Geez, so it decided yesterday to not boot up at all, it would draw 20v at 1,5amps, but then cut out.
I put my finger on the cpu and in the few seconds that it was drawing 1,5amps, the CPU got scorching hot... this is probably a fucked CPU...