After pressing the CPU board push button, the LED goes steady and never resumes a slow blink.

Test EPROM memory test does not pass

Cause: A bad U4 6116 RAM, or a missing select from U9/U10.

Checks

• Address and data pins on U4 should read 2 to 4 V; pins 14 and 20 at 0 V and pins 21, 23 and 25 near 0.5 V.
• Check the select signal at U4 pin 18; if missing, follow it back to U9/U10.

Fix

• Replace U4, or the U9/U10 gate whose input is present but output is not.

Systems

• Bally 6803

Related tips

• Test EPROM fitted but the LED does not blink
• Test EPROM socket signals at U3
• Bench-test a CPU board with the 6803 test EPROM
• CPU board landmarks: battery, LED, relay and ROMs
• CPU jumpers JW1-JW6 for game EPROM size
• Find a bad 6803 or a shorted bus line
• What is on the 6803 CPU board
• CPU board test points

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