820-00928 5V on DC-In

[bjf]

This board is getting 5V on PP20V_USBC_TA_VBUS_CONN. It got hit pretty hard on the bottom left corner of the back of the board. A few other spots on the back also. Top side looks clean. I included pre-ultrasonic pics. I've spent a long time cleaning up that terrible area near U3900 and U4200. Replaced everything looked bad and check for continuity and shorts. Everything looks good now. Not sure what's not working correctly here.

 

[JohnB8812]

PP3v3_G3H present at 3.3 volts? If yes, see if it bootloops any of the ports. If no, check for a short. If no short, inject 3.3 volts into that line and see if you get any current draw. If you do have a short, relieve the short

 

[2informaticos]

Looks like SMC cannot communicate with all 4 USBC controllers.
Check if something change testing all ports with charger.
You may note something heats, just test.
If the same, then start measuring resistance to ground on all power rails of U3100/200 and UB300/400.
Of course, check first voltage and resistance to ground at F7000 and L6900.

 

[bjf]

Okay, will do. Is U4200 involved in that process? I'm guessing it is and that was the area that was hit the hardest. I've tried to clean it up as much as possible and replaced any bad components.

 

[bjf]

• 2.2V on PP3V3_G3H

• Can't find anything different when powering the 4 USB-C ports.
• 5.2V on PPDCIN_G3H_CHGR.
• 4V on PPDCIN_G3H_P3v3G3H.
• No shorts on F7000 (.320 in diode mode) or L6900 (.344 in diode mode).
• .138 on all 4 power rail fuses.

 

[2informaticos]

"2.2V on PP3V3_G3H"
There is the problem.
Resistance to ground, exact value on ohm scale?

 

[JohnB8812]

Yes check for short to ground on PP3v3_G3H. If no short, as often is the case, I would inject voltage into 3v3_G3H and see if anything pulls current. In my experience, U3200 is often the culprit

 

[bjf]

2.7kΩ to ground on PP3V3_G3H. My good board is measuring 2.8kΩ.

I wasn't aware that PP3V3_G3H would still be produced even if DCIN is at 5.2V and PPDCIN_G3H_P3v3G3H is at 4V.

PPBUS is at .320 in diode mode vs a good board at .430.

All 4 USB-C controllers are measuring fine.

I've checked everything else in all of the damaged areas and anything else that seems like it could be an issue. I can't find anything off compared to my good board.

 

[JohnB8812]

All of that is normal. The reason 3v3_G3H is being pulled down is likely because either the ISL9239 or one of the CD3215 chips is pulling it down. In my experience, U3200 pulls it down most often. I would inject 3 volts into PP3v3_G3H and monitor if anything pulls current. Your PPBUS being slightly low could point to the ISL9239. One of those is likely pulling down PP3v3_G3H and DCIN.

 

[2informaticos]

Your case is not simple. You don't have a pure short, nor low value to ground on that line.
Very likely nothing gets hot injecting tension.
You may have luck if is an IC and enters in some kind of avalanche when injecting voltage, even if no low ohmic value there.
If not, you can inject voltage and wait 10min (maybe more) and try to find at least an area with few degrees more than the rest of board. Remove CPU heatsink in such case.
A thermal camera can help in this case. Or use the lips, instead of fingers, to check board temp...