After being off a while the game fails to boot; turned off and on again, it comes up.

Game will not boot after sitting off, but starts on the second try

Cause: A reset section capacitor, usually C30 (22 mfd) and possibly C29 (100 mfd).

Checks

• Bridge C30 with a known good 22 mfd capacitor and see whether boots become reliable.

Fix

• Replace C30, and C29 if needed.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C

Related tips

• "Adjust Failure" at power-on
• Won't boot after restoration, new EPROMs fitted: try the original ROMs
• Won't boot even with a new CPU board and new chips: the new ROMs were bad
• Occasional U10 PIA error at power-on, but the game plays
• MPU won't boot even though a test ROM passes every PIA and RAM: bad game ROMs
• Game will not boot consistently: power-on reset (POR) circuit
• Four beeps at power-up, GI only and no display: game has no batteries
• Spinner works in switch test but scores nothing in play: factory reset

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Two, Clay Harrell (pinrepair.com)