Macbook pro 13'' A2338 late 2020 stuck at 5V

[mariusm28]

Hi,

I bought a waterdamaged macbook pro A2338 , late 2020 EMC 3578, its stuck at 5V 0,06mA.
The 3V8 (U5700) chip is shorted out, atleast the PPBUS_VMAIN_VIN_ISNS Cap is and a bunch of resistors. It also seems that a resistor is missing. Does anyone have a boardview to tell me wich resistor goes where arround the U5700?

And for the macbook to boot it requiers 20V am I right? Wich chip tells the charger that it is a Macbook and not a phone?

Thank you so much!

[mon2]

Re: Macbook pro 13'' A2338 late 2020 stuck at 5V

which chip tells the charger that it is a macbook and not a phone?

cd3217 @ uf400 & uf500.

Confirm the LDO rails on each CD3217 but proceed with great care as to not short anything.

For the 20V to be negotiated, each CD3217 (aka ACE controller) needs to be functioning as well as the local flash rom needs to be operational.

Q: What is the voltage @ PPBUS_AON before and after F5200 (fuse) ?

For now, U5200 will take in 5V and BOOST the voltage to create PPBUS_AON.

Once 20V is supplied by the external power adapter, then U5200 will act like a buck regulator (high input voltage to a low output voltage) and supply again the PPBUS_AON rail.

[mariusm28]

Re: Macbook pro 13'' A2338 late 2020 stuck at 5V

Thanks for the quick answer!

I measured 5V1 on F5200 both after and before the fuse.

CC331, C7742-C7746 al measure 4 ohms to ground. I guess there are many more shorts in this circuit. Allthough the damage is nearly invisble I hope U7700 is still healthy.
I'll try and look for a short around U7700. Same for UC300.

[mon2]

Re: Macbook pro 13'' A2338 late 2020 stuck at 5V

Start slowly to locate the source of the shorts.

See attached.

If you remove RC327 (0201 = tons of fun). Where is the short now ?

Is it on CC331 or AFTER the RC327 part you just removed ?

My bet is on the downstream bulk caps as per attached.

[mariusm28]

Re: Macbook pro 13'' A2338 late 2020 stuck at 5V

Thanks alot for the information and help!

It's going to be a challange. As I was measuring, CC333 just crumbled to dust. RC327 seems fine. I do have to check if the removal of RC327 clears the short on the caps. Bulkcaps CC335 and CC334 measure 4 Ohms. I reflowed UC300, didnt remove the short on CC331. I say short but I measure 4 Ohms over CC331.

I'll get back to you shortly!





To get back to your first few questions:
F5200 measures 12v both before and after the fuse. I confused it with FF200. UF400 and UF500 both get 5V1 and CF405 gives me a clear 1V5. CF505 however measure wierd, voltages vary between 0,300/0,155.

[mon2]

Re: Macbook pro 13'' A2338 late 2020 stuck at 5V

CF505 however measure wierd, voltages vary between 0,300/0,155.

Remove CF505 and see if this LDO rail is restored to 1v5.

Likely the ACE controller UF500 is defective if this LDO rail is not stable like the other controller.

From memory, believe that the 1v5 rail is used by ACE controller for the BMC communication (CC1 / CC2 pins) -> regardless, each ACE contoller must be working to allow for the 20V contract to be negotiated.