820-00840 no boot!! A BIG MISTERY

[phantomEVO]

motherboard super clean...i don't know the history..

i have ppbus_g3h at 13v fluctuating

20v on both usb ports...

from power supply, it seems to reboot in loop like you can see her

https://www.dropbox.com/scl/fi/8urbo...=xlamh0kw&dl=0



In this video you can see also the motherboard under thermal camera


after dismantled from the frame,...i don't know what happen: now i have 5v on both ports...ppbus_g3h is 0v (no shorted)

with battery connected, .ppbus_g3h is 1,3v

3,3 1,1 1,8 present on both controllers but unstable....like in loop

display of amp meter power off and then on in loop after 4/5 seconds

SMC_RST is 3,0v unstable

[mon2]

Remove all power. Meter in resistance mode.

Measure the resistance to ground of PPBUS_G3H @ fuse F7000. What is the resistance in ohms?


Connect the power adapter.

Share the voltage to ground of the following:

PPVIN_G3H_P3V3G3H @ D6905, pin # 3 - stable?

PP3V3_G3H @ R6999 - stable?

SMBUS_BATT_SCL ; battery connector
SMBUS_BATT_SDA ; battery connector

[phantomEVO]

Remove all power. Meter in resistance mode.

Measure the resistance to ground of PPBUS_G3H @ fuse F7000. What is the resistance in ohms?


Connect the power adapter.

Share the voltage to ground of the following:

PPVIN_G3H_P3V3G3H @ D6905, pin # 3 - stable?

PP3V3_G3H @ R6999 - stable?

SMBUS_BATT_SCL ; battery connector
SMBUS_BATT_SDA ; battery connector

resistance to ground of PPBUS_G3H @ fuse F7000 70K
PPVIN_G3H_P3V3G3H @ D6905, pin # 34,75 NOT STABLE
PP3V3_G3H @ R6999 3,4 NOT STABLE
SMBUS_SMC_5_G3H_SCL 0,430K
SMBUS_SMC_5_G3H_SDA 0,430K

[mon2]

Remove all power. Meter in resistance mode.

Measure the resistance to ground of D6905, pin #3.

[phantomEVO]

I REALLY don't understand




[URL unfurl="true"]https://www.dropbox.com/scl/fi/gasqw54fwf4bt6udr8mqt/820-00840-2.mov?rlkey=w6a7y1zd9svxbtfqp18bb8mgm&st=py1tnl05&dl=0[/URL]


pin 3 35k 0,556 in diode mode

[mon2]

Check this:

https://repair.wiki/w/MacBook_Pro_A1..._at_20V_repair

[phantomEVO]

Check this:

https://repair.wiki/w/MacBook_Pro_A1..._at_20V_repair

you see the video? because sometimes i have (totally random) 20 v, but then after some seconds goes to 0 and then to 5v...

most of the time i have 5v with the amp meter that reboot it self after some seconds in loop

ps i have not PM_EN_P1V8S0

[phantomEVO]

i really don't understand!!

https://www.dropbox.com/scl/fi/xx7fv...=rrq8q06a&dl=0

[mon2]

https://logi.wiki/index.php/CD3215_Bootup_Sequence

[phantomEVO]

what should i check ?

[mon2]

Everything. Start at the top of the checklist.

[phantomEVO]

UPC_XA_GATE1 4,8V

UPC_XA_GATE 0V

UPC_XB_GATE1 10,9

UPC_XB_GATE2 6,3V

SMC_RST (i've found SMC_RESET_L) is 0V and not 3,3

[mon2]

Ok. Confirm (without power) that the resistor @ R7072 is present on the board. Confirm the resistance of this part is ~1k ohms. Confirm that you have the same incorrect voltage @ R7072, pin #1.

re: your post # 7 - yes, you do have this in the design.

Label is PM_EN_P1V8S0.

[phantomEVO]

Ok i've done some magic (rehot both usb controller) and now i have (i hope) 20v rocksteady on both ports, but no boot




You see here the amp meter




[URL unfurl="true"]https://www.dropbox.com/scl/fi/ul599f9jp9thqpuf9i8k0/820-00840-4.mov?rlkey=gd8pla7y94c4mi9ers4zbjrrv&st=cfhcinkb&dl=0[/URL]

[phantomEVO]

ppbus_g3h is 13v

pp3v3_s5 and pp5v_s5 presents

[mon2]

Good job on the 20v fix.

Attached.

[phantomEVO]

sorry mon, what should i do now with all those schematics^

[mon2]

The numbers inside each circle indicate the order of the sequencing performed by this board. Starting with (1) - the 5 volt rail is supplied by the power adapter, etc. You will need to review each step to determine at which point the board stops to boot. From your posted videos, the board is power cycling. You reach ~500mA and then power cycle.

You can review the board with a thermal camera to determine if you have a shorted part that is forcing an excessive current draw - perhaps even a shorted capacitor.
You can do the same by removing all power -> measure the resistance to ground of each power inductor. Each inductor is linked to a power rail. If there is a shorted part, the local regulator will power down that rail.
Perhaps an issue with the local bios.
Perhaps a missing part on a local current sense loop circuit which will force the local rail to power down again.
The posted diagrams will also help.

[phantomEVO]

this is what i see under thermal camera

https://www.dropbox.com/scl/fi/szvcn...=zbqta7c5&dl=0

[phantomEVO]

all_sys_pwrgd is 3,3 and then goes to 0