820-00850 with shorted LDOs

[borgil]

Hello all,

I am trying to repair one of my relative's dead 2018 MacBook Pro A1989. It stopped charging all of a sudden but was still working on battery until it was depleted.

It shows the following symtoms:

• Power on 3 of the USB-C ports cycles from 5V 0.25 A to approx. 1A
• On the 4th USB-C power stays at 5V 0.25A but if I flip the USB-C power plug the meter does not light up

UB300 is the CD3215 associated with the 4th port. There is no visible damage around UB300 or the port itself.

I checked PP20V_USBC_TA_VBUS and it is stable at 5V.

However PP3V3_UPC_TA_LDO, PP1V8_UPC_TA_LDOA, PP1V8_UPC_TA_LDOD, PP1V1_UPC_TA_LDO_BMC are all shorted to ground.

Do you think it is a bad CD3215 or could it be something else?

Thank you.

[mon2]

Re: 820-00850 with shorted LDOs

Yes, bad cd3215. Each cd3215 must be working to select the 20V power delivery contract.

Often the fault of fake PD chargers that are not designed properly to cut costs that kill this ACE controller.

Sourcing replacement cd3215 can be a headache. Check for a good vendor on AliExpress or use a donor board of the same and reball it.

[borgil]

Re: 820-00850 with shorted LDOs

Thanks for the lightning fast answer mon2.

I will look at vendors with good feedback to source the replacement CD3215C00 then.

Do you think it is worth checking for other components that might have been damaged now or is it better to wait until I have replaced the faulty CD3215?

[mon2]

Re: 820-00850 with shorted LDOs

Remove all power. Meter in DIODE mode.

Red probe, yes red to ground.
Black probe to pin to test.

Check the diode readings of CC1 and also CC2 pins of each CD3215 controller.

Post each measurement. Suspecting that the non-functional port will have different readings.

See this excellent webpage and case studies on this topic:

https://logi.wiki/index.php/CD3215_Bootup_Sequence

[borgil]

Re: 820-00850 with shorted LDOs

Thanks again.

Here are the readings:
USBC_TA_CC1 = 0.57 V (takes time to stabilize)
USBC_TA_CC2 = 0.48 V (takes time to stabilize)
USBC_TB_CC1 = 0.61 V
USBC_TB_CC2 = 0.61 V
USBC_XA_CC1 = 0.60 V
USBC_XA_CC2 = 0.60 V
USBC_XB_CC1 = 0.61 V
USBC_XB_CC2 = 0.61 V

Definitely different. So diodes QB630 and QB640 have also gone bad?

Thanks for the pointer to the Wiki. This is the page I used to start troubleshooting but I stopped measurements at step 2 when I saw all LDOs were shorted.