Another way to have fun with this is to make the attract mode playable.
You can do this using the MAME debugger console by adding the following lines:
bp 80,1,{pc=87 ; g}
bp 1977,1,{pc=197a ; g}
You can also enable sound in attract mode with this line:
bp e9,1,{pc=eb ; g}
I will see if I can find another hack to make it so the game doesn't freak out when jumpman makes it to the top in attract mode.
edit: found it. The following hack fixes attract mode if jumpman should finish the level:
bp 746,{b@600a==16},{b@600a=5; g}
More fun with attract mode. Set the screen played:
bp 770,1,{b@6227=2 ; g}
The above code sets the screen to 2 [conveyors] during attract mode. Change the 2 to 3 for elevators, or to 4 for rivets.
Don Hodges