Switch matrix connector voltages under the test EPROM

With the test EPROM blinking fast: J3 pins 4-15 read 1 to 2 V, pin 1 +5 V, pin 2 0 V. J4 pins 2-15 read 1 to 2 V; J4 pin 1 is +5 V with W8 fitted (lower with W9). J5 pins 7-15 read 1 to 2 V, pins 1-2 +5 V, pins 3-4 0 V, pin 6 unused. A pin that is off points to its PIA or series resistor.

Systems

• Bally 6803

Related tips

• Flipper switch shorting into the lane change switch
• Why strobe 5 needs its jumper when it has switches
• Switch column 5 dead after swapping in a CPU board
• PIA outputs not toggling under the test EPROM
• Unplug all but J1 when using the test EPROM in the game
• Bench-test a CPU board with the 6803 test EPROM
• CPU jumpers JW1-JW6 for game EPROM size
• Test EPROM socket signals at U3

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