According to at least 2 people on this site... this is the Super Nova's pinouts.
1 = Up
2 = Down
3 = Left
4 = Right
5 = button (1)
6 = button (2)
7 = button (3)
8 = button (4)
14 = button (5)
15 =button (6)
16 = GND
17 = (Start)
18 = (Coin)
19 = +5 VDC
20 = none connected
21 = none connected
22 = none connected
23 = none connected
24 = none connected
25 = none connected