820-00875 PPBUS_G3H boosting after liquid damage

[nik1981]

Now to find a UK supplier of the chip

 

[nik1981]

Replaced U7000. Getting 5v on VDDA & VDDP now. Still have an issue with PPBUS_G3H as it?s jumping between 3.6v and 12.95 continuously.

I can?t get it to start in SMC bypass either, I just get a fast fan for 2 seconds and it goes off again

 

[nik1981]

20.3v dcin now though

 

[nik1981]

ALL_SYS_PWRGD is jumping from 0v to 3.2v continuously also

 

[nik1981]

Ive taken F7000 off the board to see if PPBUS_G3H fluctuates on the pin one side of the fuse when its not continuing on to the system. Its still fluctuating but not as much (or my meter can't see it) it looks like its going from 7v to 12.95v repeatedly

 

[2informaticos]

You must get stable PPBUS_G3H when F7000 is removed (pad 1).
If not, check other volyages for U7000...

 

[nik1981]

I'll check the voltages into U7000 then.. problem is, I'm not 100% sure what they are meant to be for some

 

[nik1981]

While testing the voltages, U7000 stopped working again. I got 20.2v on pin 10,15,20 before it stopped. I ordered two U7000, so I guess I'll be changing it again

 

[2informaticos]

Reflow the one you have on the board now.
Random function can be generated by bad solders...

 

[nik1981]

Tried that but no change. Just trying the second one now

 

[nik1981]

The other one was giving a happy dance while reflowing so it should have been okay solder wise.. I probably poked something I shouldn't while testing I imagine

 

[nik1981]

New one on and back to 20.2v but still have PPBUS_G3H fluctuating on pin 1 of F7000

 

[2informaticos]

Post again basic voltages for U7000.

 

[nik1981]

VDDA Pin 2 - 5.02v
VDDP Pin 17 - 5.02v

PPDCIN Pin 10 - 20.2v
TBA_CSIR_N Pin 15 - 20.2v
TBA_CSIR_P Pin 20 - 20.2v

TBA_AUX_DET Pin 18 - 5.01v
SMC_AUX_OK Pin 28 - 3.396v

 

[nik1981]

LX1 Pin 31 is fluctuating between 0v and 36mv
LX2 Pin 6 is also doing the same

Thats only with a multimeter though so it may be jumping higher but its too quick to catch

 

[2informaticos]

3V42 and SMC_RESET_L stable high?
Check for any moved component around U7000.
R7020 gets steady 20V?

 

[nik1981]

If you mean 3v3_g3h on pin 30, that is stable at 3.396v
SMC_Reset_L is also stable at 3.396v

I can't see anything wrong around U7000

R7020 is a stable 20.2v on both sides

 

[nik1981]

I started testing all caps and resistors on the PBUS side between U7000 and F7000, found R7062 (which should be a 1ohm 0201 resistor reading as 147ohms so U7000 probably thought there was a ton of drain with that at 147ohm.

Swapped R7062 out and now I have a solid 12.95v on PPBUS_G3H up to F7000

Now to reattach the fuse and cross my fingers

 

[nik1981]

Damn it.. I get noise to say the charger is plugged in and an apple logo for 1 second

 

[nik1981]

Seems the keyboard is interfering. If I disconnect the keyboard, it turns on fine and stays on. Power button held on maybe.

Anyone know what to short to trigger the equivalent of pressing the power button? I don't have a spare keyboard for this model.