Atari System-1 Motherboard Pinouts ================================== P108 Video ---------- 1 Video Return 2 Blue 3 Green 4 Red 5 V Sync 6 key 7 Comp Sync 8 H Sync P104 Input ---------- 1 +5 2 Coin Counter 3 Coin Counter 2 4 N.U. 5 Self Test 6 Aux Coin Switch 7 N.U. 8 Key 9 Left Coin SW 10 Right Coin SW 11 Gnd P105 Sound (note outputs are line level and need an external amp to drive a speaker) ---------- 1 Self Test 2 Right Return (ground for audio) 3 Right Audio (to amp section on AR/III board) 4 Left Return (ground for audio) 5 Key 6 Left Audio (to amp section on AR/III board) P101 Power ---------- 1 Return (ground) 2 + sense 3 +5 V 4 +10.3 V Reset (unreg) 5 - sense 6 -15 V 7 unused 8 RTN (ground) 9 +15 V 10 +5 V 11 +5 V 12 Return (ground0 Control panel wiring varies from game to game... Here's what's on the schematics: J106 ------ 1 +5 2 n/c 3 LED 2 4 LED 1 5 Key 6 SW 5 7 SW 2 8 SW 4 9 SW 1 10 SW 3 11 GND J102 ------ 1 +5 2 Up 2 / Vert. 4 3 Dn 2 / Horz. 4 4 Lt 2 / Vert. 3 5 Rt 1 / Horz. 1 6 Rt 2 / Horz. 3 7 Lt 1 / Vert. 1 8 Up 1 / Vert. 2 9 DN 1 / Horz. 2 10 Key 11 GND J103 ------ 1 +5 2 Horz Clk 2 3 Horz Dir 2 4 Vert Clk 2 5 Vert Dir 2 6 Horz Clk 1 7 Horz Dir 1 8 Vert Clk 1 9 Key 10 Vert Dir 1 11 GND