[help]820-01700 "mistery problem"

[phantomEVO]

Hi to all, i don't know the real history of this board.

the technician who gave me this board says: "i don't know the history of this board, it not switch to 20v. i have changed ub300 and ub400, than i've discovered to have short on 5v andi i have changed u7650. still 5v not switching"


so under microscope i've found

- shorts on rb246,rb401,rb400

- u7650 (tps51980b) changed with (tps51980A)

- j6640 melted (maybe some one has reflowed or changed u3100 or u3200?)

so i've bouth another identical board anche changed all 4 usb controllers respecting the order., installed tps51980b and removed all shorts

then i've changed u2890

after this, finally switch to 20v but no boot

like you see here.

https://www.dropbox.com/scl/fi/8tssh...=5f5pb348&dl=0


i'm stuck, i don't know what to check

i have no 0,9/1,8/2,5 on nand

i have no shorts around nand...i'm missing something

those voltage are not present even when i try to restore in dfu

i've tried to restore in dfu mode with error 4042...


help!!

[phantomEVO]

1,8 3,3 5 g3s not present

[mon2]

Measure the resistance to ground of each and every inductor on the board. Each inductor is linked to a power supply. You may have a shorted part on one or more of these power rails.

[phantomEVO]

inductors are all goods....maybe i'm missing some power rail?

[mon2]

What is the voltage to ground of PPBUS_G3H?

[phantomEVO]

ppbus was shorted!

PPBUS_G3H_SSD0_SNS and PPBUS_G3H_SSD1_SNS

removed cleaned and reballed u9580! no short anymore on ssd0_sns ! still short on ssd1_sns. reballed u9800 still short. changed with another one from a donor board, short disappeared and ppbus_g3h not in short! amps draw is different but no boot! under camera i see u9080 becoming super hot! but no shorts around...it

https://www.dropbox.com/scl/fi/k4cfw...=6xjjypd0&dl=0

[mon2]

If PP2V5_NAND_SSD1 is truly not shorted, suggest to replace U9080.

[phantomEVO]

ok changed u9080 with another one that doesn't warm up.

ppbus is 12,3 but unstable

https://www.dropbox.com/scl/fi/02tp4...3iqv4z&dl=0

[phantomEVO]

PP2V5_NAND_SSD1 is 68 ohm

[mon2]

Do you now have a stable voltage on PP2V5_NAND_SSD1?

[phantomEVO]

i have no voltage at alll

[mon2]

Measure the voltage to ground of the following:

SSD_PMU_RESET_L

SSD1_VR_P2V5_EN

SSD1_VR_P2V5_EN_R

PPBUS_G3H_SSD1_SNS

[reformatt]

Personally, I wouldn't spend much time on a board that's been fucked with and has this many issues. When I get a board 2nd hand, you can guarantee they have tried to do a DFU with a fault present. This just makes it worse as you now have a T2 that potentially has a corrupted ROM. 68 ohms sounds too low on the NAND's, should be 170 ohms or so at room temp. Check all other NAND power rails as well and compare to the openboardview diode readings.

[phantomEVO]

i'm an idiot, because i've tried to reprogram t2 rom with a dump from internet.

i have had a lot problem writing it with my minipro ....so according to this video,

https://www.youtube.com/watch?v=8x15Ye406uY

i've bought a ch341 programmer. it seems to program the chip without problem, but now the macbook is DIRECTLY in dfu mode, and trying to reflash it with apple configurator,, it give me everything error 4014 (like it can't exit from dfu). i've tried even with my original dump, wihtout luck..

[phantomEVO]

now, i'm waiting t48 programmer....hoping this is only a programming problem....

do you have a 100% WORKING T2 ROM DUMP?

[mon2]

T2 reflash request was suggested about 50+ posts ago in the original thread.

[phantomEVO]

i don't understand: could you explain me better mon?

[phantomEVO]

Personally, I wouldn't spend much time on a board that's been fucked with and has this many issues. When I get a board 2nd hand, you can guarantee they have tried to do a DFU with a fault present. This just makes it worse as you now have a T2 that potentially has a corrupted ROM. 68 ohms sounds too low on the NAND's, should be 170 ohms or so at room temp. Check all other NAND power rails as well and compare to the openboardview diode readings.

you are right, but i would like to fix it!!!

know removing and reflashing soc rom with another dump, i have done big mistake, because now it goes directly in dfu and obviously it doesn't flash corretly t2 give me error 4014.....

i've tried to reflash my original backup, but still the same...directly in dfu


i was wrong before: PP2V5_NAND_SSD1 0,43k

[phantomEVO]

i think it's normal that it goes in dfu after removing and/or flashing old buck or a dump from internet....problem is that now not having 20v anymore, is quite impossible (for me) to find the original problem...

[phantomEVO]

Help 🥲🥲