820-00239 - Stuck at 5V 0A

[Hgrimm]

Received computer from customer. No history, Just stopped charging one day and wont power on. No Liquid damage found.

Was getting 5v 0.3 amps from charger.

PP3V3_G3H was at 2.7V
No short on PP3V3_G3H.
All other lines on U6903 were present and correct.
Surrounding resistors were correct values
Replaced u6903.
PP3V3_G3H is now 0.7V
Replaced u6903 again
Same Results.
injected 3.3V to PP3V3_G3H
UB400 Getting hot.
PP3v3_UPC_TB_LDO was shorted to ground.
Removed UB400
PP3V3_G3H is now at 0.3V
Customer decided he now just wants data. Tried Lifeboat connector. nothing shows up.
Removed L6900 to see if which side the voltage drop is occurring.
With L6900 Removed. P3V3G3H_LX is back to 3.3V.
Very confused here. No shorts on PP3V3_G3H... why is it being pulled down still??
If i inject 3.3V to PP3v3_G3H the and plug in the charger.I get 20V 0A

 

[2informaticos]

First of all, welcome to the forum!

"All other lines on U6903 were present and correct."
We prefer exact readings.

Is very important to know exact D6902 I/O voltage.

 

[Hgrimm]

Thank you, pleasure to be here.

Unfortunately i failed to note the values before replacing the chip but Here are the current Values of U6902:
1: 4.06V
2: 4.27V
3: 0.34V
4:0
5:0
6:0
7:0
8: 4.27V
9: 0.1V
10: 5V

D6902:
Pin 1: 0V
Pin 2: 5.2V
Pin 3: 4.27

 

[Hgrimm]

Was cleaning up some of my soldering around U6902. L6900 split in two when i lifted it off the board. (Never seen an inductor fail like this) Replaced L6900 and All my voltages changed...

Charger is now 5v 0.03A

PP3V3_G3H is still low @ 0.89V

D6902:
Pin 1: 0V
Pin 2: 5.2V
Pin 3: 3.65V

1: 4.30V
2: 3.6V
3: 0.89V
4:0
5:0
6:0
7:0
8: 3.6V
9: 0.29V
10: 4.5V

 

[Hgrimm]

Just checked all my LDOs. U3100 seems to also be shorted to ground. Only getting 0.3V on PP3V3_UPC_XA_LDO and it has very low resistance to ground. only 37 Ohms. I think the issue is with U3100 also. You think i should remove? I really hate the under filled chips so trying to avoid removing lol

 

[2informaticos]

You must compare diode mode readings on LDO lines between all CD3215 chips.
Then you'll know which chip is bad.

Also need to change D6902.

 

[Hgrimm]

LDO Diode Mode Readings:

U3100: 0.05
u3200: 1.56
UB300: 1.55
UB400: 0 (UB400 Has been removed already due to short on LDO)

So u3200 is bad also?

 

[2informaticos]

"UB400: 0"
What should we understand?
0= 0.000 (short), or OL (out of range)???

Each CD3215 chip has 4 LDOs; 1x 3V3, 2x 1V8, 1x 1V1.
U3100 is very likely bad.
Please check diode mode correctly; red probe connected to ground!

 

[Hgrimm]

sorry, 0 was meant to be OL.
I was getting around 0.02 on 3v3 LDO before I removed UB400

only checked 3v3 LDO. Will recheck all LDO values when I'm back in the shop tomorrow.

All 4 CD3215s need to be working for 20V right? Meaning, I cant just remove the bad ICs and use the other USB C ports. I have to replace the CD3215 that are bad?

 

[2informaticos]

SMC needs to talk with all CD3215 chips before switching to 20V.
You must replace U3100 and UB400, at least.

 

[Hgrimm]

Okay, ordered some CD3215s.

Removed U3100. replaced D6902. 3v3_G3H is now 3.4V but it is power cycling. Not sure if that is a normal from missing 2 CD3215 or if there is something else i should be looking for?

Will replace both CD3215s when those arrive and update you.

 

[2informaticos]

Don't waste time until you replace the CD3215 chips.

 

[Hgrimm]

Sounds good, Will update once those are replaced. Thank you for your help! Much appreciated.

 

[Hgrimm]

CD3215s replaced. Board gets 20V and is working perfectly. Thank you again for your help. Can mark this as solved.