Fortunately I found schematics for a Percom Doubler II here and decided to build one. The provided layout is best suited for a professionally built board with plated through holes. Since I would be etching and drilling it myself I re-imported the schematic into KiCad and rearranged the layout to allow more room between ICs and fewer vias.
Some of the components are difficult to find. I was fortunate to already have several MB8876A ICs which are identical to the FD1791 using in the original doubler. A company called Mikes Arcade was able to supply the required PROM and program it as well.
|Board after exposure and developing.|
|Ferric Chloride warming up in a water bath.|
|Replaced socket with pin connector.|
|Board in position.|