Mod4: convert a -17 or M-100 to take 2732s at U2 and U6 (runs any Bally game)

Steps

• Links needed: E1-E2, E3-E5 (check this one twice), E6-E7 and E8-E10.
• Solder side: cut the trace to U2 pin 21. Component side: cut the trace to U2 pin 18 between U2 and U3.
• Solder side: wire U2 pin 18 to U2 pin 12, and U2 pin 21 to U9 (the CPU) pin 24.
• Solder side: cut the trace to U6 pin 21. Component side: cut the trace to U6 pin 18 between U6 and U5.
• Solder side: wire U6 pin 18 to U6 pin 12, and U6 pin 21 to U2 pin 21 so both pins 21 reach U9 pin 24.
• Solder side: cut the traces to U17 pin 2 and U18 pin 4, then link those two pins to each other with wire (page 10).

Systems

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

Related tips

• A Stern M-200 set for 2732s runs any Bally or Stern game 1977-1985
• Mod2: one 2732 at U2 on a -17 or M-100 (combines U2 and U6 code)
• -17 and M-100 boards cannot run 1979-1985 games without modification
• Bally -17 and Stern M-100 ROM jumper settings
• Mod1: two 2716 EPROMs at U2 and U6 on a -17 or M-100
• Test EPROM: the least an MPU needs to run it
• Run Freedom or Night Rider on a -17 with 2716s at U1 and U6
• U9 pin 2 (halt) is not high

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