before the summer heat makes it uncomfortable to use the soldering iron, I would like to share my latest project: Apple-1 2513 CHAR ROM Replacement.
There are already a few around, I know, but this version takes into account the unique conditions of the Apple-1, meaning the presence of negative voltages on certain address lines of the ROM.
That' s not unusual, it's that way "by design" and as long as you're using 2513 ROMs there are no problems.
Troubles can come when using traditional EPROMs (2716) or EEPROMs (2816), which do not like the negative voltage input at all.
And since signal conditioning is always a good thing, I decided to add a bunch of Schottky diodes that I had in my drawer: problems solved.
You can find all you need for the realization, including diagram and PCB, at the address:
You can find also a small video with the prototype in use.