820-2936 - No USB

* Liquid damaged board (mostly SMC area)
* None of the USB ports are working, 5V present.
* No keyboard/trackpad (likely USB related)
* Both USB hubs (4600/4650) seem fine visually.
* Working fine otherwise (limited testing w/o USB though)

It seems to me that the USB link between PCH and these hubs has a problem. Not sure how to continue though.


Staff member
"Both USB hubs (4600/4650) seem fine visually"I would like to have such eyes to check components w/o any measurments.
Please check diode mode to ground on all data lines of USB ports.

Your problem is probably U2600/50 related; inspect for corrosion.
Webcam and Bluetooth not working too?
"Both USB hubs (4600/4650) seem fine visually"I would like to have such eyes to check components w/o any measurments.
Sorry, I meant to say U2600 and U2650. Visual inspection is easy BTW and one of my most successful tools in my tool bag. I wasn't suggesting they are working correctly, but merely that they have no burn marks and were not directly affected by the liquid.

Anyway, testing webcam and bluetooth is currently impossible as I'm missing both internal and external keyboard possibilities.

Data line diode mode measurements on USB hubs:
1.723 T29 N.726 BT N
2.723 T29 P.726 BT P
3.548 IR N.700 TPAD N
4.547 IR P.697 TPAD P
6.725 EXT B N.574 EXT A N
7.725 EXT B P.574 EXT A P
30.518 UP N.519 UP N
31.518 UP P.519 UP P

Seems weird to me that the external ports w/o anything connected would show up with different values. EDIT: NM, EXTA has the debug IC in line.
EDIT 2 - missed two lines:
Last edited:


Staff member
Do you get correct VDD3.3 and xFILT voltages for U2600/50?
Check if 24MHz oscillation is present at Y2600/50.
Inspect all solders, traces and surrounding components in the USB hubs area.
PINU2600U2650Known good
14 CRFILT1.25V1.27V1.23
34 PLLFILT2.91V3.21V1.18
ALL VDD 3.33.3V3.3V
CRYSTAL0MHz / 0V0MHz / 0V24MHz / .9V

PLLFILT voltage looks high, as this is connected to a 1.2V regulator. This also is a likely reason for the lack of freq/voltage on the crystals. Seems unlikely to me that they would both die at the same time.

Hub areas looks fine, no obvious issues.
Changed the chips, but that did not bring much improvement. Gave up on this one because I didn't have much faith in it becoming a trust worthy board. Thanks for the help anyway.