AppleII_KiCad1.png

Hello!

I've got what I believe to be a 100% accurate KiCad Schematic of the Apple II Revision 0 system board.  To do so, I did the following:

1.  Downloaded the KiCad schematic for the Apple II+ from https://github.com/baldengineer/bit-preserve/tree/main/Apple

2.  Reverted the schematic back to the R0 schematic as per "The Apple II Circuit Description" by W. Gayler.

3.  Imported the Gerber files for the system board as created by Mike Willegal.

4.  Added footprints for the components.

5.  Added the footprints to the imported gerber files to ensure accuracy.

6.  Fixed various schematic issues.

I didn't upload the board file as the gerber import messed up the thickness of the traces, so it needs extensive re-work to set the proper thicknesses.

Link: https://github.com/baldengineer/bit-preserve/tree/main/Apple  (Local Archive, 2024-01-20)

PIA_Pin17.jpg

A few simple checks using an oscilloscope can reduce the number of suspect IC(s) in an Apple-1 to a few, which then can be swapped against (hopefully) good ones. Key is the isolation of subsystems (such as the DRAM) which can interfere with the proper execution of diagnostics in PROM. This approach works best with diagnostics firmware in PROM which does not need any functional RAM in the machine.