MacBook Pro 2017 board 820-00928 with missing PPBUS

[sekidata]

This board has me stumped. It came from an A1707 15” machine with a battery issue (I believe it had the wrong battery connected to it, or its battery connector was shorted).

The board was stuck at 5V USB-C. I found a short on PP3V3_G3H which I traced to a shorted SMC. I replaced the SMC, which restored PP3V3_G3H to 3.3V and SMC_PM_G2_EN to 3.4V.

Now when I plug in a charger cable, the USB-C port initially stays as 5V and after 10-15 seconds jumps to 20V. I’ve never seen a delay this long; I’m sure it means something.

PPBUS_G3H is not being generated, even with 20V on PPDCIN_G3H. I replaced U7000 (ISL9239) with no change.

Current sensing resistors R7021/22 are fine. CD3215 LDOs are all fine.

 

[2informaticos]

Did you test now with good battery?
Be sure to use original 87/96W charger.

Check SMC_USBC_INT_L level.

 

[sekidata]

Yes, I use an original Apple 87W charger.

When I connect a battery instead of charger, I get PPBUS = 11.7V. The SMC is off.

SMC_USBC_INT_L is 3.4V with charger connected.

 

[2informaticos]

"The SMC is off."
Not sure what this means.

With battery connected, check U7800 LDOs.
With charger only, check CHGR_AMON/BMON and SMC_BC_ACOK.

 

[sekidata]

With battery connected:
PP3V3_PMICLDO: 3.3
PP5V_PMICLDO: 5.0

With charger connected, here are the output voltages for U7000:
SMC_BC_ACOK: 3.4
CHGR_AMON: 0
CHGR_BMON: 0
SMC_CHGR_INT_L: 0
SMC_RST_L: 3.4
PM_EN_P3V3_G3H: 5.2
TBA_VDDA: 5.2

 

[2informaticos]

With battery connected, trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L.
Also check for pulse at 3V3_S5, at same time.

 

[sekidata]

With just the battery connected, PP3V3_S5 and PM_PWRBTN_L are 0V. Triggering SMC_ONOFF_L doesn't change that. When I additionally plug in the charger, I get 3.4V on PP3V3_S5 and PM_PWRBTN_L but no pulse or drop when I trigger SMC_ONOFF_L.

 

[2informaticos]

You may try changing SMC and/or U7800.

 

[sekidata]

Ok, I poked around on this board a bit more to find out why PPBUS was not created. I found the data lines SMBUS_SMC_5_G3_SCL and SMBUS_SMC_5_G3_SDA shorted to ground (3Ω and 22Ω). Obviously, the SMC could not communicate with U7000.

I found diode D6950 shorted to ground and replaced it. This restored the SMC data lines, PPBUS, and PP3V3_S5. Now I’m stuck in S5, still troubleshooting.

 

[2informaticos]

Did you try original 87/96W charger?

 

[sekidata]

Yes, Apple 87W.

 

[2informaticos]

Is the battery charging now?

Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L, at same time.

 

[sekidata]

I checked all power rails that U7800 (PMIC) produces and I was missing several (PP1V2_S3, PP1V8_SUS, PP1V0_SUS). So I replaced U7800, as you had suggested before. Now all power rails are back, the machine starts up and is fully functional. Thanks!