Apple 16" macbook pro 820-01700 stuck at 5v

[razer94]

Hi I have a 820-01700 board that will not boot. Can yall guide me on trouble shooting. It has had previous water damage but was cleaned and working until recently
It is taking 5v through usb-c and taking 0.05a

PPBUS_G3H - .297v
F7000 resistance to ground is 33ohm
PPDCIN_G3_CHGR - is 5.07V

I'm not sure how to proceed at this point any help would be appreciated

[mon2]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

See attached.

Remove the 2 fuses @ F7000, F7001.

Then power up again and measure the voltage to ground of PPBUS_G3H @ pin # 1 of F7000 or F7001.

Post your measurement.

PPDCIN_G3_CHGR - is 5.07V

Check again after the above fuses are removed.

[reformatt]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

If you are lucky, most common issue is a shorted cap on PP2V5_NAND_SSD1 (C9091, C9092 etc) or worst case, U9080 has decided to short out. The low impedance on PPBUS_G3H isn't a great sign though. Check around the NAND's and U9080 for a short.

[razer94]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

See attached.

Remove the 2 fuses @ F7000, F7001.

Then power up again and measure the voltage to ground of PPBUS_G3H @ pin # 1 of F7000 or F7001.

Post your measurement.


Check again after the above fuses are removed.

So with both fuses removed voltage at pin #1 is 12.31v. So I am assuming that that side is okay?

[mon2]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

PPBUS_G3H is better but still not the correct voltage.

See here:

https://boards.rossmanngroup.com/thr...s-12-3v.62475/

1) What is the rating of the power adapter being used? It should be 96W or higher.

2) Is the adapter @ 20V now or still @ 5v for the input voltage ?

[razer94]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

I'm using a bench power supply with by-3200 power cable.
Input voltage is still 5v

[mon2]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

If I understand the BY-3200 power cable correctly, your bench power supply is dialed up to 20 volts ? That is, if the logic board is truly requesting 20V, this BY-3200 will supply it?

The logic board should be @ 20V but only if the ACE controllers are working properly.

Check the voltage to ground of each of the LDO rails on each ACE controller.

[razer94]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

Should i still check this with the fuses still removed.
And yes the power supply is 20v and if it need 20v it will supply

If I understand the BY-3200 power cable correctly, your bench power supply is dialed up to 20 volts ? That is, if the logic board is truly requesting 20V, this BY-3200 will supply it?

The logic board should be @ 20V but only if the ACE controllers are working properly.

Check the voltage to ground of each of the LDO rails on each ACE controller.

[mon2]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

Yes, fuses off since the consumer side of ppbus_g3h has a short.

The adapter voltage should be 20v if the ace (cd3217) controllers are working. Check the LDO rails of each cd3217 ace controller.

[piernov]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

PPBUS_G3H must come first to feed power to T2 for USB-PD negotiation.

[razer94]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

so with fuses removed is there no point to measure the LDO at the ACE controllers?
Low impedence in the G3H line is still another problem too

[razer94]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

So i measured the resistance from c9091 pin 1 and c9081 pin 1 and there is 6ohms.i I also see 27ohm from c9091 to ground. Does this mean the NAND is gone?

[reformatt]

Re: Apple 16" macbook pro 820-01700 stuck at 5v

So i measured the resistance from c9091 pin 1 and c9081 pin 1 and there is 6ohms.i I also see 27ohm from c9091 to ground. Does this mean the NAND is gone?

Usually yes. Very common issue unfortunately. The buck converter shorts PPBUS directly to the NAND's. Game over and you have to replace all 4 from another board. Really bad bad design.

Remove U9080 and see if your partial short on PPBUS is gone. If it were just one of the 2.5V caps shorted, then you wouldn't have the short on PPBUS_G3H. This points to failure of U9080 and destruction of the NAND's in turn.