Gregory's Serverahh that makes more sense. there are a few higher current connections, but more importantly, there are cuts in the ground plane! this creates a star ground at the large highlighted pad near the middle. this is the negative battery terminal (but after the current sense resistor)
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 i haven't reverse engineered many 4-layer boards, but i'm kinda amazed it worked out this well. @tubetime Amazing job, would love to see a video on how exactly you go about it. reassembled like a magic trick. the layout CAD was quite helpful for finding footprint locations.  @tubetime That's amazing. What's the quote? Ah, yes. "Sometimes, magic is just someone spending more time on something than anyone else might reasonably expect." -- Teller @tubetime Wow. How in the world do you figure out the middle layers? It’s a good thing this one was only four - I think some modern PCBs are 12+ layers. The aim is not to be able to re-make a PCB, but just to be able to debug one? @gogobonobo the thread explains how i did it. higher layer count boards require more invasive methods. but yes i wanted to be able to debug boards corroded by a leaking capacitor. |
anyway, i could fix up a few footprints but this reverse engineering job is essentially completed. you can find the design files here: https://github.com/schlae/Thinkpad700CPower