The Z23 game PROM

The 18-pin bipolar game PROM at Z23 holds only the game rules; blanks and programmers are gone, and it runs hot and often fails. The board boots, runs audits and tests and takes coins without it, but starting a game plays the start sounds and then locks up. A 24-pin 2716 EPROM on an adaptor board can replace it.

Systems

• Gottlieb System 1

Related tips

• Using the "T" test PROM
• Diagnostics run without the game PROM
• Spare chips for System 1 boards
• The six Rockwell "spider" chips on the CPU board
• Which spider chips fail and why
• Swapped U4 or U5 spider still does not work
• Check the TC3 jumper plug on the CPU board
• Odd high scores usually mean a bad 5101 RAM

Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)