As base I used a 3U rack with aluminum casing. For the backplane I used VG32 (DIN 41612 Type C 32 pins) and columns a and c are connected (effectively only 16 connections left). A specially made transformer is used as power source with the mains connector and power switch at the back of the rack. The transformer has (at 230V primary voltage) the following secondary voltages:

12V AC
12V AC
24V AC
20V-0V-20V AC

The first 12V rail is converted to 9V DC with the help of a rectifier and a LM350K voltage regulator. All voltages are secured with a 2A fuse and are connected to the backplane as follows:

Reihe Funktion
12ac  +9V DC
10ac GND
4ac 25V AC
24ac 25V AC
16ac 0V AC
18ac 20V AC
20ac 20V AC
28ac 12V AC
32ac 12V AC

And here some pictures