Clock and reset are good but the CPU still will not run the test EPROM.

Find a bad 6803 or a shorted bus line

Cause: A bad 6803, a bad U5 or U6 latch, or a short on the board pulling a bus line down.

Checks

• Measure U1 pins 21-40 with a meter: each should read 2 to 4 V, except pin 39 at about 1 V.
• A missing signal on pins 21-29 points to the 6803; on pins 30-37 to U5 or U6.
• For other missing lines, bend the pin out of the socket and re-measure: still missing means a bad 6803, present means something on the board is shorting that line.

Fix

• Replace the bad chip, or track the short by lifting or cutting connected parts one at a time.

Systems

• Bally 6803

Related tips

• Bench-test a CPU board with the 6803 test EPROM
• What is on the 6803 CPU board
• Power a 6803 CPU board on the bench with a PC supply
• CPU jumpers JW1-JW6 for game EPROM size
• Test EPROM fitted but the LED does not blink
• Test EPROM memory test does not pass
• Interrupt circuit failure from the 2x12 VAC signal
• CPU board test points

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