G'day mate,
The pop bumpers and flippers are fine and strong. I'll try and do what ajlaird suggested and get some voltage readings tomorrow, if I can figure out how from the schematics. This is all pretty new to me.

One more question. Should the DMD make a humming noise? It's not that audible with the backbox closed but when you open it, it is quite noticeable. The pitch of the sound changes every time the display changes.

Thanks everyone for your help, it is greatly appreciated.