I first tried to load the RetroPi software on an old Raspberry Pi 1 B+ that I had laying around. This worked and I was able to play Space Invaders using an Xbox controler and my workshop computer speakers, though it was really pushing the Raspberry Pi to its limits.

I tested this on my old portable black and white CRT TV.

I was able to get a hold of a Rasperry Pi 2 to use instead which made a big difference to the speed of the software.
I purchased a HDMI to VGA adaptor from eBay so that I could connect an old 3:4 computer monitor to the raspberry pi.

I purchased all the parts needed for the control panel from Altronics. I had to replace the wire connectors that attach to all the switches because the cables that came with the control board didn't fit. I then cut a temporary control panel out of MDF using the laser cutter to fit it all on.

