Macbook 820-00239 missing PPBUS

[drmacbookth]

Hi guys, I have an 820-00239, customer said it stopped working after an update. Since this is not a T2 chip version I dont think its a software issue. The machine takes no charge 5.12v, no amp on all ports. I measure as follows:

PP20V on C3201: 5V
PP3V3_UPC on C3208: 3.3v
PP3V3_G3H on C3200: 0v (no short)
PPBUS: 0.014v (no short)

Next I checked U6903
L6900: 0V (no short)
PPVIN C6906: 1.33 (no short)
Enable signal: 2.22v (Assume this means U7000 is OK?)

Next I checked U7000:
all resistor measure OK and looks very clean
I have tried to replace it, as a lucky shot but all values remain the same as above.

I cannot find any short on all big coils as well. Suggestions as what to check next, or if I forgot something in my work flow above?

 

[2informaticos]

"PPVIN C6906: 1.33 (no short)"
Post diode mode reading, red probe connected to ground.
Do NOT assume that only pure short is bad!

Check R/D6902; post their voltages.

 

[drmacbookth]

Here you go:

Diode reading: 0.135
R6902: 0 ohm, 5.18v
D6902 pin 1: 0v
pin 2: 5.18v
pin 3: 1.31v

 

[drmacbookth]

Here also the other diode readings for D6902:
Pin 1: 0.455
Pin 2: 0.542

 

[drmacbookth]

I found R6907 was at 22ohm, replaced it and now back to 2.2ohm, didnt fix it though

 

[2informaticos]

"Diode reading: 0.135"
As expected, too low value!
Remove C6905/6.
If still low, replace U6903.
D6902 MUST be replaced too; is now burnt.

 

[drmacbookth]

Values seem OK after removing the 2 capacitors. Only issue is my only donor board has no D6902, will report back when I get my hands on one.

 

[drmacbookth]

820-00165 seems to have the same spec, so I used that one and, it works thanks bro your a genius!

 

[2informaticos]

I bet only one cap was bad.
For the future, remove components one by one and check every time the result.

 

[drmacbookth]

Yes the one near the IC. Got another one today with a bad cap in the same line and easy fix using the same strategy, thanks again!