2MB RAM card missing GND to top pin of J5

[RolandJuno]

Hi there! I built one of the 2MB RAM card clones but it just would not work in my Lisa. I even swapped every SIMM and IC from a working original SunRem 2MB RAM card with no luck.

I did a lot of logic traces and it came down to a missing GND connection to the top pin of J5, which I believe should be tied to ground but it's just an isolated VIA (confirmed on the gerbers). Adding a bodge to that pin to GND and the card works 100%.

There's also some errors on the main logic schematic.

• G8 is a 74S00 and G3 is a 74S02. The pin names are wrong but the pin out/numbers are correct. The was confusing to identify inputs vs outputs as I was troubleshooting.
• G6 pin 10 connects to G1 pin 8.

On the board, the silkscreen at the top should say RP3-7: 33 Ohms (not 330).

Hope this helps!

[warmech]

Hello!

I'll have to take a look at these this weekend - I thought I had ironed out all the issues, as all of my cards have worked so far. I'll investigate my EDA files and see what's up. Thank you for letting me know! I'll update you when I have some answers.

Edit: Also, I'm in the process of migrating everything to KiCad for the sake of standardization, so this will get revisited regardless at some point. Thank you again for the heads up, as I'd have just reconstituted the issue there as well.