820-3437 dont turn on

[Dozer]

got this macbook air with liquid damage

cleaned it in ultrasonic, after visual inspection dont found anything what immediately catches the eye

orange/green light on macsafe
3.42V present
PPBUS_G3H is 1.5V

open the F7140 is 8.52V

there is no short to ground in PPBUS_G3H but i can measure only 0,110 in diode mode, should be about 0,165

pulles out F7700 but same result

measured resitance on L7130, about 150 ohm, a good board shows about 500

with thermal camera i found Q7630 goes about 45 Grad Celsius

After replacement of Q7630 I go 500 ohm resistance and a fan spin

but seems still like brain death, measured on the U6100 pin 5, 6,7 got in diode mode high value (more than 1.04...

Tryed another u6100 from 820-3437 programmed it with the clear me , now, diode values are good. starting the board fan is spinning, after about 8 sec it turns off and start again

soldered back the "old" u6100, now here the values pin 5,6,7 are good as well
but board starts and thats it fan spins, after a while with full power, nothing happens and no cycling.


need some help please

 

[2informaticos]

This board should restart 2 times before turns on.

If Q7630 was bad, there is a big chance to have bad PCH.

Check all SPI Bus Termination resistors and their traces.
Clean J6100, if looks uggly; remove it, if not possible to clean properly.

Did you reball SMC?

 

[Dozer]

ok. before i replaced Q7630 the PCH was heating up quick to about 45C
J6100 removed already
SMC not reballed

 

[Dozer]

found no problems with SPI Bus Termination resistors
so i decided to replace the mainboard, i think you are right, PCH is bad