Because FedEx is failing twice, lying once, and sure taking their sweet time to do their one job, recapping the LC 3 board has been delayed. So, I serviced its floppy drive! Cheese wheel replaced (and I'm out of new wheels), everything cleaned and re-greased up, drive works!
(To use it on the Plus board as I'm doing, I've read you need to use the Plus flat cable, with yellow stripe, not the LC 3 one, red stipe, otherwise the eject motor runs continuously. Didn't test but FYI) #retroApple
Ok I just had to test my theory about the LC 475 with the broken trace… and theory proven! 😁 The DRAS[0] line comes from the opposite end of the board to pin 4 of the first RAM chip, and from there it connects to the second, third and so on. The connection between the first and second chips is broken. If I patch it, the machine boots perfectly using only the on-board RAM!
Since both chips are close together I can fix this with a wire when I recap. Cool cool! #retroApple
The LC 3 board bug is clearly visible here. See how the -5V trace goes to the + side of C22. That's wrong, since the other side is the ground plane, so -5V is negative relative to ground. The capacitor should have the + side to the ground.
This was not just an assembly mistake, the silkscreen is wrong as well, so it was a project error.
And this is why I'm in software, so things can be patched after the fact. 😅 #retroApple
Lots of this will be new territory for me. Including soldering SMD caps (I have replaced SMD caps by through holes but that would offend the gods on this boards). I admit I am quite afraid of breaking them but you only learn by doing so… let’s goooo!
The other machines are two LC 475s. One has a broken trace on the RAS line for the onboard RAMs (under a cap, of course). The other has messed up video, and I still didn’t find what the problem is. Probably broken traces as well. #retroApple
LC TDK 699-0153 PSU Since there doesn't seem to be a lot of information on these LC power supplies, I thought I would share what I've been working on the past few months. My next goal is figuring out what everything on the board does in order to ease diagnosis, unfortunately I don't know much...
I can of course get 3 MeanWell PSUs that fit the LC PSU cases but that is another PITA in some ways (holding them in place, cabling etc).
I may be overthinking this. But I love this HW so much I don’t want to destroy it with a dumb mistake out of ignorance. #retroApple
Miguel Arroz
