MacBook PRO M1 A2338 stuck at 5V

[Mabot17]

Hello,i want to repair this mainboard mod.820-02020.It is visually speaking in perfect condition,no signs of damage burn,no spilled,no corrosion,and i'm pretty confident that nobody has opened the device before.
The problem is that is not booting at all,and it's not boosting to 20v.
Can you help me to do a correct diagnose of main voltage rails (AON and others),to track down the issues?
i have tools boardview and schematics so i can do measures no problem,
i know that i can do that and learn with your help,
one important note
i attach pics of the two usb-c ports that are drawing different currents at 5v(stable and not floating up and down).
thanks

[Mabot17]

I found this cap near UF400 that is almost short in diode mode,it reads 0,0046v(those caps nearby reads ok in diode mode CF409 CF405 CF505 CF508 CF509,they reads all about 0,500v ).

[mon2]

Flux and carefully remove this cap. Then test the pcb pads without power if the short is gone. Test the logic again with your power adapter.

[reformatt]

Openboarddata for that cap lists diode mode as 0.5V. It's an internally generated 3.3V LDO rail from the CD3217 so with any luck it's a shorted cap on that rail (e.g. CF408 or CF260). Other components from this rail are resistors or the EEPROM UF260.

From experience with the T2 machines, the T2 power sequence stops when one of the CD3217's isn't talking. M1 should be the same.

[Mabot17]

Thank you for the help guys,i removed the cap,but no luck hehe line is still shorted.Cap is good and it should be 10uf if i measured it right.

[Mabot17]

Hmm what you suggest now? Remove UF400 to confirm that is internally shorted?Something else?what EEprom UF260 does to CD3217,is that some sort of bios?I saw a guy on youtube that sell a programmer for UF260 to solve 20v boosting issue,could it be related to my problem?

[mon2]

What is the voltage to ground of PPBUS_AON @ F5200? Check both sides of this fuse.

What is the resistance to ground of this rail? Measure in ohms.

Would you have an adjustable power supply? If the short's resistance is low enough then you can inject 1 volts onto this shorted rail and check who is heating up. This ACE controller may be defective.

Re: Your last post, wait on this reflash issue. The flash that is needed to boot the firmware for the 20V resides inside the part that is powered from this missing 3v3 LDO rail. So this rail must exist first before the firmware can load to bump to the 20v power delivery contract. In summary, your flash may be ok.

[Mabot17]

PPBUS_AON reads 12,27V on F5200 fuse.RTG is high on both sides,circa 0,8 Mohms.
Ok injecting a bit of current is a good idea,so if only the cd32 will heat up i will know for sure that is defective?

[Mabot17]

Ok it seems that UF400 is heat up in the left upper part of the chip,it does not draw much current,power supply set at 1V 1A,it only drops voltage from 1v to 0,8v and heats up,but i’m not 100%sure because i use a shortkiller and current is pulsating injected due to avoid short damage,but something is really going on that chip

[mon2]

The current setting for the injection tool is low. We also have the shortkiller but it can spike upto 20A / 30A varying with the purchased model. Allow this tool to support higher current then you will know for sure. The suspect is with this power delivery controller. Be sure to review how to purchase a spare of this part because being a more recent model of the logic board, there are many restrictions on which exact part can be used onboard. From my understanding, you need to be sure the part is from a donor board of the same model for starters.

[Mabot17]

Aww that is a bad news,because i don’t have a donor board,hmm maybe i will try gambling on Aliexpress or some ebay seller that has it on stock

[Mabot17]

hi I found a new CD3217 chip on ebay, I replaced it, the short disappeared, now I have stable voltage values in both controllers. 3.3v and 1.5v on the input caps are now present and I also have a stable 5v on the 2 output fuses. PPBUSAON measures stable 12.27v, 3.8v and 5V are present and stable on the coils. Unfortunately, however, I'm still stuck at 5v and the board doesn't boost at 20v. I don't know, it could be the chip is not compatible, or is the card in DFU? how can I check?

[mon2]

The boost process is configured over the SMBUS lines of these buck/boost controllers ISL9240/ISL9239, etc.

Carefully, measure the voltage to ground of:

PP3V3_UPC0_LDO ; powers the SPI Flash BOOT rom for the firmware used by the CD3217 ACE (PD) controllers

I2C_SMC_PWR_1V8_SDA
I2C_SMC_PWR_1V8_SCL

I2C_SMC_PWR_3V3_SCL
I2C_SMC_PWR_3V3_SDA

[Mabot17]

Measured at test points,
3,255V and 1,794V stable
PP3v3LDO gives 3,437v stable.

[mon2]

Can you attempt a DFU? We will know if there is an additional fault or not based on this next step.

Do review this thread as well:

A2338 820-02020-A 5V, no screen, unable to revive/restore - Badcaps

Be sure that your USB Type C cables are suitable for 5A power delivery support = 100W rated.

[Mabot17]

Good day,actually i’m using this setup to power on logic board,DC power supply set on 20v 3A,and BY-3200 power cable.

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of each inductor on the board. Checking for low resistance measurements. List all suspected inductors.

[Mabot17]

All big coils are pretty high resistance,and i also measured coil soc and ausiliary power supply voltages using this template and they are all good and stable

[mon2]

Try a DFU.

[Mabot17]

Can you explain me how to do the DFU?