820-02098-a A2442 No Power / Boot

[economypilot]

Good Afternoon!

I am new at this. My kitty cat spilled a glass of wine on my Macbook. Recently divorced and ex took like 80% of my assets and is still suing me ---- and I need this laptop to defend myself. The 20% I "got" is tied up in my house. Anyway - I have to fix this on my own if I'm going to have access to my files. I'm fairly logical and think I'm capable. I have a hot air station and have done quite a bit of soldering as I've built drones before, but I've only done minimal SMD work.

My charger doesn't light up when plugged in, and I do have a USB-C meter which shows the board is stuck at 5v and draws .006 amps.

I have my boardview and schematics and I have confirmed there is a short between ground and my PPBUS-AON.

I have visible corrosion around the components shown in the attached files but I am confused by the boardview in that location. The components in the boardview file are shown installed at angles that are not present on my physical board and appear to be different. This is what is throwing me off in moving forward at this point... do I have a slightly different board, or am I not understanding the boardview diagram?

I'm attaching 3 images. A view of my physical board and the corrosion present, a stock image of my board with the area in question circled, and then the boardview file circled in the same area which seems to show a different layout (unless I have some ignorance about this).

I guess I should also mention I have a Fluke 289 as my meter and I DO actually have a thermal camera although the one that I have is more geared toward building maintenance and construction I think it is sufficiently sensitive to be of help in making diagnostics.

 

[2informaticos]

First of all, welcome to the forum!

That corrosion should be the reason of the short.
RP850 is practically connected to PPBUS_AON.
Clean that area and rebuil the traces, if necessary.
Then check if the short still persists.

Many boardviews have strange representation for several transistors and ICs.
That shouldn't be a problem to locate the signals by their names, not by components.

A2442 - 820-02098 - M1 Pro.rar

drive.google.com

Use this one, if you prefer...

 

[economypilot]

Okay - I cleaned up the area shown above. Still had a short on PPBUS_AON. Opposite side of the board had a very obviously blown capacitor (CN479) that I pulled off the board. I think I messed it up by lifting it early and the board was in rough shape (pics attached). Boardview showed that the capacitors in that group were electrically isolated. I pulled the others off as well doing a much better job and the pads for all 4 were showing shorted together. I confirmed this was the sole short on PPBUS_AON by removing the FS200 and FS201 fuses and injecting 2v which of course lit the short at the pads up like a Christmas tree on my infrared camera but I saw no other shorts. So I really cleaned that area up with solder brade the best I could until I got about 6 ohms resistance between the positive capacitor pads and ground at which point I reinstalled them all, replaced the fuses, etc. and with injected power saw no heat signature. However - my usb-c meter is still showing the board stuck at 5v .006 amps... and I'm getting 0v to the FS200 / FS201 fuses.

So that's were I'm at so far. I guess my questions are:

- Is 6ohms an appropriate reading for the capacitor pads for the group that includes CN479? Or is that too low and indicative of remaining damage to the silicone in my picture? I did improve things with my solder braid as it was a dead short before... but if that *is* a problem does the board look repairable and do you have advice about how I would go about that?

- Do I have another problem to solve first if I'm not getting any voltage at FS200 when powering from my usb-c cable? I *am* using my power brick to attempt power.

I know I did a number on the pcb at that first capacitor I think my heat gun has like waaay less power than the ones shown in your videos it takes mine a long long time to get things to lift, even with preheating.

PS - I found the OpenBoardData tables with the diode readings so I've measured that at FS200 / 201 and for PPBUS_AON and got a reading of .0062, far lower than the table of 1.578. So I moved upstream. readingst at chgr_aux_det and chgr_aux_det_3v3 are okay. But working my way toward PPBUS_AON on the schematic I get a little lost in the logic gates about where I should be troubleshooting.

 

[2informaticos]

6 ohm to ground at PPBUS_AON is practically short.
Check if any coil gives you the same reading.

BTW, I can't find FS200/1 in schematic; do you mean F5200/1 instead?
Once removed, the short remains on pad 2?

 

[economypilot]

Hello! I did mean F5200/1 sorry about that. The 6ohm short remains on pad 2 with the fuses removed.

I checked all of the coils and they all have readings in ohms that are much higher. The lowest reading was still several hundred ohms. I identified the coils visually -- all the gray squares. I couldn't figure out a way to search boardview for part type... but I got all the ones I can see of the various sizes.

So that's where I'm at. Did you see the picture I took of the PCB I damaged at CN479? Just wondering if I exposed the ground plane or something and that although I reduced the conductivity with my cleanup efforts there's still inappropriate conductivity happening there.

Thanks for your help!!

 

[2informaticos]

You must be sure there is no short between the first two copper layers.
Polish that area, especially the edges of any hole in the board.

 

[economypilot]

okay. I went to town on the hole with a micro carbide bit in the dremel. First it dropped back down to a dead short, which was sad. But under the theory that you can't break it if it's already broke I kept going and now have a reading of 26 ohms. It'll be a neat trick getting one capacitor to bridge over to the other pad and solder them together but I think I can manage that. But is 26 ohms in the range of what we'd expect to be appropriate?