820-01949 - Only 1 USB-C port goes to 20V. Board won't boot

[overshoot]

Hello,

I've got that 820-01949 that has liquid damage on both side of the board, close to the air intake.
Customer live on an island and the humidity is always a concern here, in conjonction with dust.

Damages on one side are:
- R3208
- R3209
- C3102
- C3512

Damages on the other side are (close to the USB_C rom):
- RB298
- RB293
- RB29C
- RB262

I have replaced those but I am getting only the UB3100_T chip that works and gives me 20V.
Issue is, once it goes to 20V, the amperage jumps to 100mA and then falls back 0.
I was able to charge the battery with this battery however board would not power on.
Board might be in DFU but since the needed port for DFU which is UB3100_X is only giving me 5V 200ma, I assume that won't work to allow me to DFU restore or am I wrong?

The other side where the Rom resistors were completely corroded and traces gone and that I did rebuild still does not give me 20V.

I went ahead and replace the UB3100_X from a 820-01700, same side, same port (lower port) as I've understood this is the way to go but same behavior.

Any hint on what I could do or check next to get UB3100_X to work?

 

[2informaticos]

5V is good enough for DFU.
But I expect to have more components affected by corrosion.
Possibly accumulated crap underneath CD3217 chips too.

 

[overshoot]

Thanks!

I've already replaced the chip which has 5V so far with one from a 820-01700 as I mentioned in my previous post.
I've tried to get it to DFU but my other Mac doesn't see it.
I am wondering if I've used the right chip or if I should transfer the pair of CD3217 with the Rom.
I've used U3100 from a 820-01700 to replace UB3100_X from my faulty 820-01949.
Can you please confirm that?

 

[2informaticos]

Not sure if this transplant is good.
You should use chips from same model donor board.

Did you try DFU before replacing the chip?
Tried forcing with external switch method?

 

[overshoot]

I went back at it and got one side (both ports) to get 20V.
The side with U3100_X and U3100_T.
However the amperage jumps to 200ma and then drops to 30ma.
Then the port cycles and back at 0ma and jumps to 30ma. It does that in a loop.

I've tried a DFU revive and then restore but it ends up with error 4042.
I've tried a couple of times, same error. At some point during the revive/restore process the trackpad stops clicking.

Since I have the other side with damaged rom chips and data lines that prevent the USB-C circuit to get 20V, I am wondering, would that cause the DFU restore to fail or is the issue lying somewhere else?

 

[overshoot]

Well I can answer my own question.
Yes fixing the other side USB-C circuit did indeed allow the computer to boot up right away without going through DFU.
Case closed.