[help] 820-01958 dead: 20v not switching

[phantomEVO]

Mon: I don't understand: Why should I put it in dfu? With its original rom it switch to 20v and try to boot!

https://www.dropbox.com/scl/fi/mid7t...=qlwapj9j&dl=0


it goes directly in dfu if I use a different rom taken from internet!

AND IT STAYS AT 5V!

[phantomEVO]

ok if i try to force it to dfu mode, it goes, but after a lot of time, it give me error 4042.....

[phantomEVO]

mon?

[phantomEVO]

is it possible that i'm missing some power rail? i'm missing P5VG3S_EN signal too

[mon2]

Confirm each of the rails on u7800 noted on this webpage:

https://repair.wiki/w/MacBook_Air_A2...VG3S_EN_repair

[phantomEVO]

All present (bootlooping) except

• PPVDDCPU_AWAKE ~ Normal voltage ~ 1.06v

it is 0,75 boot looping

[mon2]

Measure the resistance to ground level of:

PPVCC_S0_CPU

Repeat to test in diode mode. Post each measurement.

[phantomEVO]

96 oh, 0,236

[phantomEVO]

at the beginning i had

5v on both ports, stable voltages but PP3V3_G3H unstable from 2,52 to 2,66 and ppbus_g3h@ 12,31

no change after reprogramming u4770 with a dump from internet

no change after changing u7650

PP3V3_G3H fixed at 3,3 and all voltages stable chaning u7800 but still 5v on both ports

device recognized in dfu...error Unexpected device state 'DFU' expected 'Recovery' (Probably forced into DFU mode externally) [com.apple.MobileDevice.MobileRestore – 0xFAE (4014)

no dfu anymore after reflashing u4770 with my original backup

all voltages present but in loop. both ports now at 20v

[phantomEVO]

what do you think if i try to see if it goes to dfu erasing the eeprom?...i don't what else to do

[phantomEVO]

just a an annotation....pp3v3_g3h_rtc is super stable, even ppbus_g3h

[mon2]

Review this thread:

https://boards.rossmanngroup.com/thr...roblems.61662/

[phantomEVO]

the machine isn't in dfu mode....with original eeprom...

at this moment, all main voltages are present but goes to zero,

both ports are @ 20v

pp0v9_ssd not present. line is not shorted , is diode value is 0,480

[phantomEVO]

with eeprom erased, always error 4014 (dfu logo disappear and reappear super fast then error 4014 (unexpected device status dfu expected recovery). all voltages STABLE


SAME IDENTIC VOLTAGE OF THE LINKE YOU GAVE ME:
PP1V2_AWAKE 1.2V

PP1V8_AWAKE 1.8V

PP3V3_AWAKE 3.3v

PPVDDCPU_AWAKE 0.755v

PPVDDCPUSRAM_AWAKE 0.802v

PP0V8_SLPS2R 0.800v

PP1V8_SLPS2R 1.8v

PP1V25_SLPS2R_SMC_AVREF 0.234v

PP1V1_SLPS2R 1.1v

[mon2]

What about:

PPVCC_NAND_SSD0
PP0V9_SSD0_S4E0_VDD_PLL
PP1V8_VCCQIO_SSD0
PPVCCQ_ANI_SSD0

[phantomEVO]

Why don't you care about PP1V25_SLPS2R_SMC_AVREF ??? 0,234 exactly like the macbook in the post you have linked me?

changed u4780, no i have 1,24v on PP1V25_SLPS2R_SMC_AVREF 0.234v!!

eeprom repogrammed ! still no boot

here power metere:

https://www.dropbox.com/scl/fi/zgfty...=x6f01hvt&dl=0


ppbus_g3h is "unstable" because it goes from 12,31 to 12,4 to 12,59 without any logic and come back to 12,31 (with charger and battery). with charger only, stable at 12,31

all other voltages, still in loop: from the right voltage to 0

[mon2]

Error 4014 is often NAND related so best to check their voltages are present and stable.

Remove all power. Meter in resistance mode. What is the resistance measured across C7020? This is the battery current sense resistance path.

[phantomEVO]

Don't you remember that all voltages are unstable?

[phantomEVO]

resistance measured across C7020 is 2 ohm

[mon2]

Good measurement. The battery charge leg is the proper resistance.

Repeat for Vin into the PPBUS_G3H regulator (U7000) and measure across C7023. This should also be 2 ohms.