5101 RAM at U8 fails often; speed matters

The 5101 RAM at MPU U8 is a frequent failure, so keep several. Replacements must be 100 to 300 ns; the Stern M-200 MPU needs the faster 100 ns parts. Plug-in substitutes built on a 6116 RAM or static RAM exist, some with an internal battery good for about seven years.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Related tips

• Two flashes only: U8 5101 RAM
• Keep spare 6800, 6821 and 5101 chips
• Game keeps resetting: replace the 5101 RAM (an NVRAM works)
• Odd high scores usually mean a bad 5101 RAM
• System 6 won't boot and fails the 5101 RAM test even after replacing it: bad 5101 stock
• Boots into audit mode every power-up with good batteries: bad 5101 RAM
• Locks up when a second game is started: bad 5101 RAM
• Game always powers up in audit mode: bad 5101 memory chip

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)