Based on the Issue 4 schematic and the layout from photos of an issue 4 board.
fit either LK1 or LK2 depending on the type of CPU Board:
fit LK1 for 6502 CPU Board
fit LK2 for 6402A CPU Board (1 or 2MHz)
fit LK3 to select either 3.5" or 5.25" floppy drives
This latest version includes my fix using an additional AND gate which makes 3.5" drive operation 100% reliable, see details here.
Schematic
Bill Of Materials
Blank PCB
