Mod1: two 2716 EPROMs at U2 and U6 on a -17 or M-100

Steps

• Check that all four links are in place: E8-E10, E6-E7, E3-E4 and E1-E2.
• Solder side: cut the trace to U18 pin 4.
• Solder side: wire the via above U3 pin 6 (the one whose trace you just cut) to U18 pin 5, linking U18 pin 5 to U2 pin 18.
• Solder side: cut the traces to U2 pin 21 and to U6 pin 21 (page 8).
• Solder side: wire U2 pin 21 to U2 pin 24, and U6 pin 21 to U6 pin 24.
• For Freedom or Night Rider, put the 2716 that would have gone in U1 into the U2 socket.

Systems

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

Related tips

• Mod3: 2716 at U2 with a 9316 at U6 on a -17 or M-100
• Using the test EPROM memory test
• Setting up an MPU for the test EPROM
• Making the test LED for the test EPROM
• U9 signals with the test EPROM running
• U6 select signals with the test EPROM
• Checking the PIA outputs with the test EPROM
• Never use a TMS2716 EPROM

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