Apple II Motherboard (Revision 0)
A new schematic capture from the Red Book, combined with Mike Willegal's PCB layout.
Dependencies
Status
The schematic has been captured from the Red Book and checked against the existing PCB
layout. Errors were found in the schematic, which was then adjusted to match the PCB.
(Working computers have been built with this PCB layout, so it is presumed to be correct.)
All components used are in my PartDB, and most have ordering information for at least DigiKey available. A few have ordering information for other distributors where DigiKey didn't carry them, and then there are the no-longer-manufactured components that will require substitution or locating new-old-stock or used parts on eBay or whatever.
I believe the 8T97 can be replaced with the 74LS367, which is pin-compatible and still in production.
The 8T28s can be replaced with this module, which uses 74HCT1G125s and 74HCT1G126s (four of each) to the same effect.
The 2513 can be replaced with a 2716 in this adapter.
A very small number of component footprints were adjusted to work with the components that are available in 2025. Off the top of my head, the video output connector and the trimmer capacitor are no longer available. Also, the footprint used for TO-92 packages was changed to one that is included with KiCad.
The +12V stub traces to each DRAM chip have been realigned.
Redundant GND and +5V traces have been removed. The zone fill that has been added will make these connections.
add_sockets.awk
This script might be useful for other vintage-electronics projects. It will scan your PCB file for DIP-chip footprints, raise the chip model by 4 mm, and place a socket model underneath it so that 3D renders (whether the Alt-3 live render or a STEP model) will show socketed chips. It's smart enough to not try to add a socket to a socket that's been manually placed (this project uses five sockets to hold RAM configuration jumper blocks and to serve as the keyboard and joystick ports), but it's not so smart as to not duplicate work it's done previously, so use with care.
Useful Links
- a similar project (links within to GitHub are 404)