840-00840-a No Power

[Ludedude1992]

Out of a 2017 MBP. No history on board.

U7650 and surrounding does show some signs that someone before me had attempted some repair.

PPBUS_G3H - 13.04V
PP3V3_G3H - 3.4
PPDCIN_G3H - 0


Suggestions on where to start?

 

[2informaticos]

Really no voltage at R7020, with charger alone?
How do you get PPBUS_G3H then?
Strange to have 13V from battery alone.

If is the case, disconnect the battery, work with the board alone on the desk.

 

[Ludedude1992]

R7020 - 0v
PPBUS_G3H - 13.04

This is with board out , no battery attached.

 

[2informaticos]

PPBUS_G3H comes from R7020; if no battery present.
There must be at least 5V!!!
Please get a better test point for PPDCIN_G3H; just to confirm.

We cannot help if you do not provide accurate information.

 

[Ludedude1992]

Sigh. My voltmeter took a dump. Haha. New voltmeter in hand.

New readings
PPBUS_G3H - 13.0v
PPDCIN_G3H - 20.3v

 

[2informaticos]

Please, put a bit more effort.
Check coils voltage.
What about 3V3_S5/SUS?
We discussed so many times about power on sequence (on the forum); which signals did you check???

 

[Ludedude1992]

PP3V3_S5 - 0
PP3V3_SUS - 0
PP5V_S5 - 8.5V

My apologies. Not really used to the newer stuff. Power alias a tad confusing

 

[Ludedude1992]

PPBUS_G3H - 13.04v
PPDCIN_G3H - 20.3v
PP5V_S5 - 8.5v
PP3V3_G3H - 3.4v
PP3V3_S5 - 0v
PP1V8_S3 - 0v
pp3v3_sus - 0v
Buf_smc_reset_l - 3.4v
smc_pm_g2_en - 3.4v
PPBUS_PMIC - 13.03v
PP3V3_LDO3V - 3.19v
PMIC_SHUTDOWN_L - 3.16v

 

[2informaticos]

"PP5V_S5 - 8.5V"
This is really strange, change U7650.
Post diode mode to ground at L7670/90.

 

[Ludedude1992]

Will do. I will update tomorrow.

 

[Ludedude1992]

I am at a bit of a loss. Before replacing u7650 today I powered on the board to do some more tests quick.

Next thing you know I smell electrical and it appears U7800 fried. No idea why. Anyways, PPBUS_G3H is now gone and short to ground. Can this BGA chip even be replaced?

 

[2informaticos]

Can be changed, of course.
Pay atention, do not stress the board too much (with heat).

 

[Ludedude1992]

I did some searching and could not find that chip available. At least in the united states.

 

[2informaticos]

Buy scrap boards from Aliexpress, is the best option to make stock.