I finished installing LED bulbs in my playfield and when I was done and tried to play a game, an odd problem cropped up.

My Eight Ball Deluxe has a 7 drop-target bank that should pop up when at the start of the game, or for a second player. It's not popping up at either time. It does pop up when doing the solenoid diagnostic test. That implies there is power to the assembly and the fuse is good, but why isn't it popping up as it should during the game?

During the diagnostic mode everything works--the targets drop one by one and once the last one drops they all pop back up.

During game play, I can manually lift them up, and they register properly when they are hit (and the voice states they are hit), but they won't pop back up when they're supposed to.

You mean that odd light that looks like it doesn't have a purpose to the front left of the machine under the playfield? Yeah, I replaced it with an LED... gulp...

But if the coil failed why is the bank popping up properly when in diagnostic mode?

Well, thank you for pointing me in the right direction! As soon as I put an incandescent bulb back in that spot everything works properly. So it wasn't that the coil failed, it was that that bulb somehow regulates electrical flow, and without it things won't be running at the proper voltage.

As xTheBlackKnightx said on another thread...

"IMPORTANT TECHNICAL NOTE:
DO NOT USE a LED in the SEB lamp, as this will not work in the circuit theory based on necessary voltage unless the circuit has been adjusted with resistance based on a standard Ohm's Law calculation. A lot of new owners do not seem to understand the SEB design technology and why/how it was used. Read the base schematics closely. The SEB lamp is part of lamp matrix, not the SDB, and does not draw power from this part of the game. The proper 6.5v from the SEB lamp is extremely important in order to draw enough current to the MOC3011 opto-isolator on the SEB and activate. I have already seen young technicians not understand these aspects and make this mistake repeatedly on this series of games.

The SEB lamp is not "just another feature lamp".