A1990 board 820-01041-A - stucks at 5V

[Vogelek23]

Hi there, got this good looking Macbook with the original fault: no power. Connected PSU and all 4 ports were drawing 450mA @5V, one of CD3215 had a burnt hole and the other one was significantly warm. Replaced all of them and now all ports behave the same: 5V @240mA (current is floating between 220mA and 280mA). When PSU is connected, there is 1/3 secs with 300mA, then it drops to 0.02A and then, it goes up to 240mA (floating). The only part which I can feel is slightly warm (just 2-3 degrees above my hand's temperature) is T2, no other sources of heat. No spillage signs anywhere.

I cannot put it to DFU - tried multiple times on the working computer so I'm sure that the method I use works 100%. A bit strange issue is that when the 2nd working Macbook is connected to that faulty one and I try to connect the charger, I cannot get the machine to draw any current (Voltmeter stays completely blank). As soon as I disconnect the cable between Macbooks, the Voltmeter turns on (no need to re-connect charger). Is it normal?

PPBUS_G3H = 12.6V and PP3V3_G3H_RTC = 3.4V. How to troubleshoot it further? Many thanks in advance.

 

[2informaticos]

Board should enter DFU with just 5V from AC2 computer.
You may need to "help" it using SWK003 pads.

Do you get all AWAKE and SLPS2R (stable) voltage?
Also check SSD voltage.

I found dead PCH when CD3215 chip got burnt with hole on it; not on this particular board, but is an option.
T2 is also directly connected to CD3215...

 

[Vogelek23]

I found dead PCH when CD3215 chip got burnt with hole on it; not on this particular board, but is an option.
T2 is also directly connected to CD3215...

It is not what I would like to hear...

All AWAKE and SLPS2R voltages are present and stable, but no SSD voltages at all (L9020/L9021, L9030, L9080/L9081). When I try DFU using the keyboard, after 6 secs it drops to 20mA and then does not return to 240mA but stays at 60-70mA.

SWK003 does not do the trick... Seems T2 went to hell.

 

[2informaticos]

Sometime SSD voltages come on after DFU revive; even not completed (getting error).
You may need to try that few times.
The problem is to get it into DFU now.

CD3215 is connected to VBUS.
When you found a hole on it, internal die was melt somehow.

 

[Vogelek23]

I found that when PSU is not connected, the 1.8V AWAKE is not present, thus I cannot get it into DFU. Is it normal? Do I understand it correct that 1.8V AWAKE should be present while the source Macbook is connected to target even without PSU connected to source? And what about battery? Should it be connected as well?

 

[2informaticos]

You can test an working T2 board and see what happens.

Only 1V8 AWAKE is missing when you've tried that connection?

 

[Vogelek23]

As supposed, T2 chip went to hell. I found a tiny surge damage on the edge of this chip. Shame I wasn't able to fix it... Mac returned to customer. Many thanks @2informaticos for all suggestions.