P20: 44-pin edge connector component side solder side -------------- ----------- +5VDC RETURN A 1 +5VDC RETURN +5VDC B 2 +5VDC C 3 +22VDC D 4 -22VDC COIN R E 5 SLAM COIN C F 6 COIN L DIAG STEP H 7 SELF TEST X INV J 8 OUT 5 (not used) Y INV K 9 BLUE GREEN L 10 RED VIDEO GND M 11 MONOCHROME VIDEO COIN CTR R N 12 COIN CTR L COIN CTR C P 13 PWR GND PWR GND R 14 +10.3 VDC UNREG Y INVERT S 15 X INVERT X OUT T 16 X GND Y GND U 17 Y OUT ~RESET V 18 E (2.4 kHz clock) -22VDC W 19 +22VDC X 20 +5VDC Y 21 +SENSE (+5V) +5VDC RETURN Z 22 -SENSE (GND) C, D, 19 & 20 appear to be unused P18: 30-pin edge connector component side solder side -------------- ----------- +5VDC RETURN A 1 +5VDC RETURN +5VDC B 2 +5VDC ~COCK C 3 +22VDC AUDIO- D 4 -22VDC AUDIO- RETURN E 5 AUDIO+ ~RESET F 6 AUDIO+ RETURN CLK1 H 7 CLK2 DIR1 J 8 DIR2 FIRE2 K 9 FIRE1 ZAP2 L 10 ZAP1 P2 START M 11 P1 START -22VDC N 12 P1 LED +22VDC P 13 P2 LED +5VDC R 14 +5VDC +5VDC RETURN S 15 +5VDC RETURN Notes: ------ "RETURN" pins are ground, but specifically for the voltages indicated. Ground ~COCK if you're installing in a cocktail table, and connect X INV to X INVERT and Y INV to Y INVERT. Hook up a 2nd set of controls to CLK2, DIR2, FIRE2 and ZAP2 and the game will "flip" for 2 player games.