Freedom and Night Rider used tiny 512-byte ROMs at U1 and U2

The first two Bally games used 512-byte 74S474 (or 7461) chips in sockets U1 and U2, plus a 2K 9316 or 2716 in U6. They can be run from a 2716 at U1 plus a 2716 at U6, or (tested by the author) from 2732s at U2 and U6 on a -17 or -35 board converted for 2732s.

Systems

• Bally MPU AS-2518-17

Related tips

• Run Freedom or Night Rider on a -17 with 2716s at U1 and U6
• Why the MPU has ROM jumpers
• How the first-flash ROM test works
• Masked ROM numbers: keep the set matched
• After the test EPROM: refit the game ROM and count flashes
• ROM and EPROM types used on Bally MPUs
• Get the MPU booting before you change any ROM jumpers
• 9332 masked ROMs can be replaced by 2532 EPROMs as-is

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