2016 MacBook Pro 15” 820-00281 stuck at 5V

[sekidata]

This is a liquid damaged board stuck at 5V. I have the option to decline repair of this board, so I need to quickly assess if it’s repairable (i.e no bad SMC/CPU/GPU/etc)

PPDCIN_G3H is stuck at 5.2V.
PP3V3_G3H is at 3.4V.
PPBUS_G3H is at 3.8V.
All four CD3215s have all LDOs except PP1V1_UPC on UB300 and UB400. No short to ground on the missing PP1V1_UPCs.

 

[piernov]

If it's only a USB-C controller problem it may turn on from charged battery.
Liquid damage should give you hint on where to look.
Compare diode mode to ground on all LDO outputs of all USB-C controllers.

 

[sekidata]

Diode mode readings are comparable across all 4 controllers (0.48-0.51).

I'm new to the USB-C models. What are the requirements for the releasing 20V from the charger?

 

[piernov]

CD3215 Bootup Sequence - LogiWiki

We have Apple MacBook and iPhone Diode readings and general fault finding information compiled by the leaders in this area

logi.wiki

 

[2informaticos]

Did you test what happen with both charger and battery connected?

 

[sekidata]

The machine's battery is empty and I have no other way of charging it; I have a replacement battery on order to test this.

 

[2informaticos]

There is a problem on the USB-C area where no 1V1 LDO present (UB300/400).
Did you compare diode mode readings on all 4 LDO rails of each cheap?

"PPBUS_G3H is at 3.8V"
On all ports?

 

[sekidata]

When I use the USB-C ports on the other side of the board, I get 1.1V on the previously missing LDOs (sorry, I forgot there are 4 ports).

 

[sekidata]

Upon further inspection, I noticed that the SMC appears to be off. Some SMC-related signals are below. What should I check next?

SMC_BC_ACOK: 3.4
SMC_RESET_L: 3.4
SMC_USBC_INT_L: 0 (briefly 3.4, then pulled low)
SMC_ONOFF_L: 3.4
SMC_WAKE_L: 2.8

SMC_PM_G2_EN: 0
SMC_S5_PWRGD: 0

PP1V2_S5_SMC_VDDC: 1.2
PP3V0_S5_AVREF_SMC: 3.0
SMBUS_SMC_4_G3H_SCL: 3.4
SMBUS_SMC_4_G3H_SDA: 3.4

 

[2informaticos]

4 ports and each CD3215 has 4 LDO rails.
Did you check diode mode readings on all 16?

 

[sekidata]

Diode and voltage measurements for LDOs

UB400
PP3V3_UPC_TB_LDO 0.503 3.39
PP1V8_UPC_TB_LDOA 0.515 1.79
PP1V8_UPC_TB_LDOD 0.479 1.79
PP1V1_UPC_TB_LDO_BMC 0.504 1.1

UB300
PP3V3_UPC_TA_LDO 0.503 3.39
PP1V8_UPC_TA_LDOA 0.510 1.8
PP1V8_UPC_TA_LDOD 0.473 1.8
PP1V1_UPC_TA_LDO_BMC 0.500 1.1

U3100
PP3V3_UPC_XA_LDO 0.502 3.37
PP1V8_UPC_XA_LDOA 0.515 1.8
PP1V8_UPC_XA_LDOD 0.48 1.8
PP1V1_UPC_XA_LDO_BMC 0.505 1.1

U3200
PP3V3_UPC_XB_LDO 0.500 3.37
PP1V8_UPC_XB_LDOA 0.516 1.8
PP1V8_UPC_XB_LDOD 0.477 1.8
PP1V1_UPC_XB_LDO_BMC 0.505 1.1

 

[2informaticos]

So you get 1V1 LDO on every port.

Still 3.8V at PPBUS_G3H?
Remove both F7000/1 and check C7050 voltage.

 

[sekidata]

No, PPBUS_G3H is at 0V now. I noticed liquid damage in the U7000 area, which is probably the culprit. But the SMC should turn on independently of PPBUS_G3H, isn't that right?

 

[2informaticos]

SMC communicates with U7000; which can block the bus, if bad.

 

[sekidata]

Update: I replaced U7000. The SMC is now on, the charger supplies 20V, and PPBUS_G3H is working.
Thank you!