Use exact chip types in the CPU clock circuit

The clock is made by Z3 (7404) and Z2 (7474). Replace Z3 only with a plain 7404, not a 74S04 or 74LS04, as the timing changes. Most other CPU chips can be LS, ALS or HCT types, which draw less power and put less noise on the 5 V line; the faster AS and F families bring no benefit.

Systems

• Gottlieb System 80
• Gottlieb System 80A
• Gottlieb System 80B

Related tips

• System 80 CPU board main chips
• Swap the three 6532 RIOT chips when a CPU board dies
• Which System 80 CPU board goes with which games
• Replace the decoupling capacitors on the CPU and driver boards
• System 80 and 80A CPU boards swap only with the matching U2/U3
• Reading the System 80 CPU DIP switches
• U2/U3 rules ROMs decide which system a CPU board runs
• System 80 CPU board revisions D102, D107 and D20869

Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part Two, Clay Harrell (pinrepair.com)