Ken, I'm probably not the System 1 expert to be answering the question, but I do have a Sys1 with a NiWumpf MkII CPU board.
The only hardware menus I know of are reached by:
1) powering on the machine with the toggle switch
2) Pressing the white button on the top inside of the coin door will step the machine sequentially into the Setup, Data, Hardware, Option, Game, and Done submenus. Press the button 3 times to see HAR DWR. I recall the that Displays will initially show in Player 2 display, Pressing the white button again will step through: lights, coil, and then the cryptic INIT e, which according to the NiWumpf manual, will restore factory defaults to the EEPROM.
I'm not at all sure if that is what Ace is referring to when he mentions resetting the NVRAM.
I could find no reference to NVRAM in the menu options on my Sys1 with NiWumpf CPU. ???