820-3332-a not turning on

[BCN_Techs]

Hi,

Got 820-3332-a that cutomer changed U8900. No liquid damage, as he says just display randomly was shutting down. Changed U8900 again with new one ( it wasnt soldered good). The machine still not turning on. Green light ok. PPBUS_G3H 2.2V and almost shorted to ground with 11ohms ground resistance.


With magsafe contected U8000 is getting warm enough. Already checked ISL 625 and 17/18 and 27/28 resistance seems to be ok. Also resistance in that area.

I guess that when was changind U8900 first time heated up too much and fucked GPU. CHecking in that area doesnt see anything strange.

Any idea?

 

[JohnB8812]

This now has a dead GPU or CPU shorting PPBUS to ground. This one is done. You can confirm by measuring resistance between the PPBUS fuse and the CPU/GPU coils

 

[BCN_Techs]

Resistance between F7040 PIn 2 and L8360 ( i think this u mean with GPU coil) is 190 ohms and with L8310 390 Ohms

 

[BCN_Techs]

what is the normal resistance value? I have 3 logic board like that all 3 dead but they all giving different values. from 300ohms upt to 3mhoms between F7040 and L8360

 

[2informaticos]

Post diode mode to ground on F7040 and L8930/60; there is GPU VCORE.
You can also remove Q8930 and check if PPBUS_G3H has then correct value.

 

[BCN_Techs]

Customer doesnt want to wait. So thanks for help, Macbook was given to it's owner.

 

[JohnB8812]

For the best they fucked it not worth the time