Macbook Pro M1 X A2484 820-02100 short on PPvin_5vusbc23 line

[fricosu007]

Hello friends, today i got an A2485 820-02100-A in a desd state, found visual short on PPVIN_5VUSBC23 line, removed tantalum capacitor, installed same same value from other donor board, now there is no short on any of the rails but when i plug either magsafe3 or usbc inget 5v stable with 0.00 amps drown, no cycle, just these steady values, board is not in dfu mode, checked with magsafe and with usbc. Only value that i find on the board is ppdcin_aon which is 5v… i dont get 3,3 aon, 3v8 aon .. all missing, where should i start looking please !

[fricosu007]

Would u5700 be the issue ?!

[mon2]

Remove all power. Meter in resistance mode.

What is the resistance to ground of PPBUS_AON_REG ?

Measure on each side of the fuses @ F5200 / F5201.

[fricosu007]

I get 0.560 MΩ on both fuses
i replaced u5700 also … same 0 amps draw

[fricosu007]

CG801 was the blown capacitor if any help

[mon2]

No shorts here with such a high resistance.

What is the voltage to ground of PPBUS_AON_REG ?

[fricosu007]

only 0.3v

[mon2]

What is the (input to the buck / boost regulator @ U5200) voltage to ground of PPDCIN_AON_CHGR ?

You can measure @ C5201 or C5202, etc.

[fricosu007]

5v

[mon2]

Flux and carefully remove F5200 and F5201. This is to remove the downstream / consumer side of this power rail. There does not appear to be a short on the consumer side of the fuses but this step will isolate this regulator. Then power up again and measure the voltage to ground of PPBUS_AON_REG.

Do review U5200 for any possible damage or on surrounding parts. You can also post close up pics of this part.

[fricosu007]

0.02v and the u5200 is mint allaround it ..

[fricosu007]

Found something new just now, UD102 BLOWN

[mon2]

This is the AHA moment

Not sure why it is damaged but will need to be fluxed and carefully removed. Be sure to allow ample time for the solder to be in liquid state.

This part is a level / voltage shifter for the SMBUS interface.

[fricosu007]

Looking now for donor boards that have this part… LSF0101-i2C
i can only find LSF0101-DRY i will check if same comonent trough the datasheets.. i dont have a 820-02100 for parts, this is a first… i will solder back the fuses and test again

[mon2]

I think it is the same. The suffix is just Apple lingo to remind the viewer that this is used for I2C level translation.

LSF0101 1-Channel Auto-Bidirectional Multi-Voltage Level Translatorfor Open-Drain and Push-Pull Applications datasheet

[fricosu007]

Yep, replaced also, still in the same state, steady 5v 0amps, so back where we have left …

[mon2]

What is the voltage to ground now of PPBUS_AON_REG ?

Test each USB Type C port -> same 5 voltage and current draw?

Rotate the USB Type C port by 180 degrees to test the bottom side of the USB C port's blade. Suggest that you unplug the main power from the wall so that the power adapter is discharged / dead -> insert onto your macbook -> then plug into the wall.

Same current draw on every port? The LDO rail of each 3217 should be reviewed to confirm the power delivery controller is functional. At 5 volts, the default power on voltage is being fed onto the logic board. The communication over the CCx pins has not taken place to dial up the VBUS rail to 20V.

[fricosu007]

Sadly i need to pause the all above for at least 8 hours since here its already midnight, my brain is fried at this point ... its nice that we create a stepby step guide to determine the solution of this issue. Many thanks for your patience, i will get back with you in 8-10 hrs !

[fricosu007]

I've managed to test all the 3127 and removed the 3128 just because i dont yet have one, inwas getting 1v3 on the ppbus_aon_reg tryed changing the UF800 just to be sure, same values on 0amps draw, 1,3 v inhave changed the raa489900 with isl9240 since from the schematics it looks the same, same result, i have replaced all the cd3127 just because i had them around, same result .. 5v 0amps the only thing that changed is the PPBUS_AON_REG that changed from 0,3 to 1v and easy increasing voltage up to 1,5…1,6v …

[mon2]

3127 and removed the 3128

3217 and removed the 3218 - took a bit to figure this out. As far as I know, you cannot expect the power delivery (PD) circuits to operate unless each PD controller is functional and onboard.

Also, not sure if raa489900 = ISL9240 so best to keep that controller to the original or source one from a donor board / reliable store on Aliexpress.