If you remove the reset board you should check to see if you need to add a resistor on the back of the MPU board. The mod id mentioned on pinwiki.com in the System 80 section.
https://pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Reset_Board
Basically add a 3.0K 1/4 watt resistor to the back of the board when not using the reset board.