820-00850-A board with CC lines issue

[sekidata]

Board had minor liquid exposure in the USB-C area of the XA port. PPBUS was 80Ω to ground. I found a shorted speaker amp (U6550) and replacing it removed the short on PPBUS.

I replaced all components with possible corrosion in the USB-C area around U3100, including the CD3215. Now, all 4 ports are stuck at 5.1V 0.26A.

I get all LDOs on all CD3215s. No shorts on CC lines (good diode mode readings). However, I only get 1.1V on the PP1V1_UPC lines on three ports; the XA port is missing PP1V1_UPC_XA_LDO_BMC. I also see normal behavior of CC1 and CC2 on the three ports other than XA.

What could cause the CC lines to malfunction on a single port when there are no shorts or other obvious issues?

 

[2informaticos]

CC1/2 lines problems usually cause black USB-C meter; as the charger doesn't properly detect the laptop in that port.
You should change that CD3215 chip; try reballing first, just in case.

 

[sekidata]

I already replaced the CD3215 twice with no change.

 

[2informaticos]

If the charger works in both ways on that port, then no CC1/2 issues there.

Check all resistors corresponding to that chip.

 

[sekidata]

Yes, charger works both ways but gets only 5V 0.26A. Resistors all check out correct.

 

[sekidata]

Here is a summary of the asymmetry that I find between the XB and XA ports:

XB readings when plugged into XB:
PP1V1_UPC: 1.1
CC1: 1.7
CC2: 0

XB readings when plugged into XA:
PP1V1_UPC: 0
CC1: fluctuating
CC2: fluctuating

XA readings when plugged into XA:
PP1V1_UPC: 0
CC1: 0
CC2: 1.8

XA readings when plugged into XB:
PP1V1_UPC: 0
CC1: 1.4
CC2: 1.4

Is it possible that the XA and XB CD3215s are not communicating properly with each other?

 

[2informaticos]

1V1 LDO only appears on the powered port.
Also CC1/2 lines from one port, are not involved on other port functionality.

Looks like you have problems with U3100 channel.

 

[sekidata]

Yes, I know. Where do I look next?

 

[2informaticos]

Check all resistors connected to U3100.
Should be good to compare diode mode readings between J3300 and JB500.
S-UEM2 is very helpful for such checkings.

 

[sekidata]

As stated before, resistors round U3100 check out ok.
The only differences between J3300 and JB500 are the DBG lines on J3300 (which I think are not supposed to be there on JB500).

 

[2informaticos]

XA CC1/2 voltages when you plug the charger into XB port are really strange.

Just in case, reflash/replace U2890.

 

[sekidata]

Replaced ROM chip U2890 from donor board, with no change.

 

[sekidata]

Waiting to hear if there is anything else to try before giving up on this board?

 

[2informaticos]

Check any power rail in that area (diode mode); even U2800's ones.
Be sure no broken trace, or ripped off components.

 

[sekidata]

Is power to U2800 needed for the CD3215s to work?

I noticed an asymmetry between these rails (on a good board these values are all the same):
PP20V_USBC_XA_VBUS: 0.18
PP20V_USBC_XB_VBUS: 0.14
PP20V_USBC_TA_VBUS: 0.18
PP20V_USBC_TB_VBUS: 0.14

 

[sekidata]

Another observation: when I connect a battery, I get the following depending which port I plug the charger in:
TA: 20V 0A
TB: 20V 0A
XA: blank USB meter
XB: 20V 0A

Without a battery present, I get:
TA: 5.1V 0.26A
TB: 5.1V 0.26A
XA: 5.1V 0.26A
XB: 5.1V 0.26A

 

[sekidata]

Also, I got the machine to start up on battery power. It shows the battery percentage but does not recognize the charger at all. The battery is not charging.

 

[2informaticos]

"XA: blank USB meter"
Both connection ways?

 

[sekidata]

Yes, both ways.
Note that I have replaced several CD3215s, all sourced from various donor boards. I now suspect that some of these were not fully functional to begin with... I will get brand-new CD3215s and replace all 4. Stay tuned.

 

[sekidata]

After replacing all four CD3215s, the situation is unchanged. One additional observation is that the bus connecting the CD3215s together (I2C_UPC_) shows values around 2V on half of the CD3215s, and 3.3V on the others. Help!