Quoted from radial_head:Triple check connector A12J/P8 and the Q and T relays as stated above. A12J/P8 and the Q and T relays carry the voltage direct from the bridge rectifiers to their proper places. Those can often times get whacked by the service bar or by the playfield being raised and put them seriously out of alignment (and sometimes causing a nasty short in the 24v circuit). Is the sound working properly?
All the info you need to trace down your issue is on 38-39 & 41-42 of your manual.
Good luck. Let us know what you find.
100% what StratDoc and radial_head said: seems very likely one of the little leaf switches that are part of the relays (beneath the main playfield, far lower-right corner) are off or not connecting. Almost the same thing happened to me (bought a great working machine, got it home, removed the playfields for cabinet work, put it back together, and then all hell broke loose and nothing seemed to work, was mostly a combination of needing to reseat the plugs and connectors AND had to clean the relays and do a slight bend on one of the switches as part of a relay). I cut up some old business cards and used the strips to "wipe" clean in between the contacts, got lots of gunk and grime off of them, wound up doing that for all of the switches and that helped with some other gremlins. HH seems like a game that doesn't like to be moved around 
So prop that playfield up to the full 90 degree position, take a close look at the relays (and with the power off manually "activate" each relay and visually see if the switches are touching as expected and possibly adjust), clean it up, have patience, keep us posted on things, and you'll be up and running before you know it!
Shakopee, MN
