820-3330 no power no orange light

[nate8organic]

Hi i have a 820-3330-B With water damage, it wont power on and only has a green light. I have checked the u6901 pin 4=3.26mv pin A & B= 3.26mv pin 5= 3.4mv & u6900 pin 4=3.72mv pin 1 =3.27mv c6908=3.4mv. is the dip in mv from 3.72 to 3.27 and 3.4mv a problem? im going to keep digging into this. any help is appreciated
Thanks
Nate

 

[dukefawks]

PPBUS voltagem should be 12.6V?
Corrosion around ISL6259?
Check R7051/52 and R7021/22 and traces to U7000.

 

[nate8organic]

okay i checked ppbus and im getting 12.56v
R7051/52 im getting 12.56 at both
R7021/22 Im getting 18.24V
The isl6259 i dont see any obvious corrosion, but this board came in a little to clean for me so i wonder if it has been cleaned before. i could replace it to test if you thing i should.
Also c7025 im getting 12.37v and 17.36v but if not mistaking that should be 10v?
and only 3.4v at C7002

 

[dukefawks]

Are you using a REAL 85W charger? It will not power on with anything less. Chinese chargers say 85W but many times they are fake 60W ones.
Is PP3V3_S5 present (L7260)?

 

[nate8organic]

Yes im using a genuine apple 85w charger. I Tested probe points 557 &365 for the L7260 and got 0v on both. So should i replace the L7260?

 

[dukefawks]

It makes no sense to replace a coil.
You test first if the enable signal is there, so is there voltage on PP3V3_S5_EN? If yes then is there maybe a short to GND on the PP3V3_S5 bus?

 

[nate8organic]

Right.
I have voltage at pp3v3_s5_EN but i cant find PP3V3_S5 bus is it spelled different in the pdf? Sorry for my inexperience, and thanks for all the help.

 

[dukefawks]

PP3V3_S5_EN does not exist it is P3V3S5_EN. PP3V3_S5 is a million times in the PDF, but it is coming from L7260.
So pin 21 of U7201(P3V3S5_EN) has 3.3V and there is nothing on L7260?

 

[nate8organic]

okay that makes sense i did assume that pp3v3_s5 was p3v3s5_EN so i had tested that correctly. im getting 3.4v at pin 21 of the U7201. but nothing on the L7260, i checked probe 365 & 557 both gave me 0

 

[dukefawks]

Looks like an issue with U7201. Measure pins 12,13,22,23,29. What is resistance to GND on L7260?

 

[nate8organic]

I tested the U7201
Pin 12 =3.49v
pin 13 =2v
pin 22 =3.3v
pin 23 =12.56v
pin 29 =5v

I tested resistance to GND on the L7260 with 16.5-16.9 ohms on both pins 1 & 2

 

[dukefawks]

16 ohm to GND on L7260 is too low. There is something not right on the 3V3 bus. You can inject 3V3 on L7260 and see if anything heats up, but 16 ohm is a semi short so this may be difficult to track down.