The Apple ProFile service manual is generous in technical detail. You want to know what you'll see on your scope when a drive read is happening? There's a picture in there. But alas, the schematic in it is for the Apple /// interface card and I need the Apple ]['s. If I want to trace it out, I'm going to have to do it myself.

And that is what I did. I pulled the card and traced it, pin by pin, net by net. This is slow, meditative work: ohm out a connection, find both ends, decide what the part actually is, and draw it. Rather than lean on generic library symbols, I
drew custom ones so that every pin carries its real function instead of a factory label. When a pin's job is "D0 read strobe," the symbol says so.

This was also my first foray in to KiCad. I've used Eagle for many many years - but their licensing changes a few years ago made it unrealistic for me to keep shelling out dough for a product I use a couple times a year. I decided to bite the bullet and figure out how to move on.

Which gave me another opportunity - scripting the state of the card. As I identified parts and interconnections, it was easy enough to build netlists in a script and have that script regenerate the whole schematic.

It took about a week in total. A lot of beeping, dragging, sweeping, head-scratching, double-checking and documenting. Pull out the netlists and build actual wiring, because that's easier for me to see while tracing something (instead of a netlist's invisible connection to three other places, I can follow the lines).

Now I wouldn't want to build a replacement from this. I wouldn't say that it's verified 100% accurate - there were definitely late nights where I was mis-documenting something that I had to come back and fix later! - but it worked for its purpose here.

This part was genuinely hard, mentally. I know that I've made absolutely zero progress on solving my problem. I decided that the tangential problem of not having the schematic was important, and it's now tackled well enough for me to move on; but my original issue is none the better for it.