820-00281 2.2V on PP3V3_G3H

EsteTron

Member
Client brought in device after device was liquid damaged. Noticed a build up of corrosion around U6903 which appears to be where PP3V3_G3H is created, and a blown Diode D6902.

First thing I did was give device an ultrasonic cleaning to remove the corrosion to get a better look. After which, I replaced D6902 since it was severely blown. Images of before and after cleaning attached below. Device still would not boot, so I then applied alcohol around there area and injected 3V using a DCPS on to D6902 and discovered that C6906 was shorted. I have removed and replaced the shorted C6906, however device still does not boot.

U7000 is sending 5V to PM_EN_P3V3_G3H to Pin 10 on U6903. (Is this voltage too high?)
Pin 2 on U6903 is being supplied 4.2V from D6902, however D6902 is being supplied 5.2V on PPDCIN_G3H.
I believe U6903 is bad and is pulling down voltage.
Pin 9 on U6903 P3V3G3H_FB is outputting 0.66V,
Pin 3 on U6903 P3V3G3H_LX Is outputting 2.2V.

USB-C Ammeter reads 5.2V with .0A consumption. I applied some more alcohol around U6903 and injected 3V on PP3V3_G3H with a .05A Consumption. I am currently waiting for some replacement CD3215 to arrive, but until then, any suggestions on what else I should be looking for? If U6903 truly is bad, I found some replacements on DigiKey.com

Thank you in advance!
 

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2informaticos

Administrator
Staff member
Do not put the board in UC to clean so small area.
Scratch with fine tip and fiber glass pen.
Then clean with IPA and tootbrush.

I suppose corroded components around U6903.
Pay atention to R6910/11/12/13.
Also be sure R6908 and C6907 are both OK.
Check traces and solders too.
If all OK, change U6903.
 

JohnB8812

New member
Yeah seeing where the corrosion was on this one, I don' think CD3215 issue even tho it is possible. Best for you to order some donors and replace what is nasty especially U6903.
 

EsteTron

Member
Thank you for your input. I will make note of the UC for the future. The other components you mentioned test out fine, so it looks like I will be ordering a replacement U6903. Is it okay for the enable pin on U6903 to be 5v? I just want to make sure U7000 isn't sending too high of a signal. Thank you.
 

EsteTron

Member
It took a while to get back to this board, however I did receive replacement U6903 chips. After replacing the chip, the board still get 2.2v. However, if I remove R6923 at the end of this circuit, the circuit gets 3.4v on Pin 1 of R6923. My thought process is that there is something pulling down voltage on Pin 2 of R6923. I then injected 3.3v into Pin 2 of R6923 which pulled at .015Amps and measured with Multi meter around all CD3215 which all received 3.3v. I am now stumped and do not know where I should be looking.
 

JohnB8812

New member
Is R6923 ok?? Did you replace any of the corroded components near U6903? My thoughts are something is definitely pulling down your 3v3 line like you said possibly a CD3215 chip OR seeing where your liquid was it could even be the ISL9239. Voltage present at pin 10 of U6903 with a good R6923 on the board?
 

EsteTron

Member
I removed R6923 from board and measured 0.4 ohms. Schematic says R6923 is 0 ohms. I did replace all corroded components except L6900, I do not have a replacement for this inductor in stock currently. I did replace U7000 just to be sure there was no internal damage. Pin 10 on U6903 is currently receiving 4.9v from with R6923 on board. I just received new stock of CD3215 from Louis's online store recently, but have not replaced them yet.
 

JohnB8812

New member
4.9 seems really really high to me.. sounds like possibly bad ISL9239 or improperly soldered ISL9239. Should be approx 3 volts on enable
 

EsteTron

Member
I thought so too when I initially measured U6930. U7000 originally was sending 5V to Pin 10 before I replaced it. Perhaps something around U7000 is putting out too much power throughout this chip.
 

EsteTron

Member
Just to rule out that there was not any internal issues with CD3215, I went ahead a replaced all 4. Board is still getting 2.2V on PP3V3_G3H. I then removed U7000 again and hooked up USB-C power supply and discovered that with U7000 removed, the enable Pin 10 on U6903 receives 1.5v. From my understanding, it should be 0v with U7000 removed. I think some extra power is somehow in my enable line. I am looking in to this line currently.
 
Hello,
Have you solved this problem?
I have 2 board 820-00923 with the exact same problem.
With the thermal camera I see heating U6903 43 ° C and UB400 / UB300 50 ° C
Enter the 0.30A on the boars
 
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