Data East made 2 machines that used chase rope light, Start Trek and Hook. Both can be trouble to repair and both have a fairly high failure rate. You know its a pain when in machine for sale ads they specifically list "Rope light works".
I've spent some time fixing my DEST lights, and I also own a Hook so I've spent some time working on chase lights and wanted to put it all down for posterity.
o DE uses 12VDC incandescent rope light containing 3 strands of lights and 1 common 12VDC power in both games.
o To supply power to the rope they take 12VDC off of the power supply CN6 pin 3 and feed the common line
o Then they 'ground' the other side of the bulbs through a unique 'chaser module' mounted in the head.
o The chaser is a simple bit of logic that grounds one side on the lamp chain as dictated by the CPU.
o The feed for these 3 'grounds' off the CPU are basically repurposed drive signals to the 'alpha-numeric display'.
Even though both machines are DMD, the CPU still has the logic and capability to drive an old plasma alpha-numeric display and DE took advantage of this unused logic.
All the CPU does to create the illusion of a 'chase' is to start repeating 1,2,3,1,2,3,1,2,3,etc,,,,,
My crappy drawing skillz...