Why strobe 5 needs its jumper when it has switches

Each strobe jumper joins a PIA output to the strobe line's blocking diode, whose anode is also pulled up to +5 V for drive current. With the jumper out the line is cut off from the PIA. If strobe 5 has switches, its jumper and pull-up resistor must be in, because the PIA alone cannot supply the current and could be damaged.

Systems

• Bally 6803

Related tips

• Switch matrix connector voltages under the test EPROM
• Flipper switch shorting into the lane change switch
• Jumper JW7 stays out
• Factory CPU jumpers by game
• CPU jumpers JW1-JW6 for game EPROM size
• Jumpers JW8-JW11 for the spare driver circuits
• PIA outputs not toggling under the test EPROM
• Electronic spares for 6803 board repair

Source: Repairing Bally 6803 Pinball Games from 1985 to 1989, Clay Harrell (pinrepair.com)