I added the keyboard overlay graphic to the link above but it will need scaling to suit the keypad - I drew it in Visio and it prints the perfect size, but saving it as a graphic changes the size for some reason(?)
I printed it on ordinary paper then carefully covered it with wide sellotape on the front and double-sided tape on the back so it clings to the keys.
Re the weird shape of the display board, its to clear the 4x4 keypad, its a bit tight as the two 6821 ports are very close and the display and keypad boards would otherwise overlap. That corner of the keypad needs clipping 45° too.
The S19 loader expects to see TTL data on keypad Port B bit 7 at 300 baud. Theres no escape from a load, so when the load is done, and the display is showing 39 which is the S19 terminator, press Reset.
Because the keypad and serial input share port B, press 'Load' first then connect the TTL serial line to B7 via an inline 1k resistor. Thats the loose yellow wire in the photo and video, I use a CH340G usb-to-serial adapter to power the board and Teraterm to optionally load S19 records.
If you're still seeing yesterdays cached version of the 6800/6802 page, just tag a variable on the end of the url, that will force a reload, like say
http://www.mccrash-racing.co.uk/philg/6800/6800.htm?k=9Cheers
Phil