I am running into this issue on a party animal. The machine was working well and then, mid-game, the coils all locked up and the playfield fuse blew. Now upon power up, every coil on the playfield and the flipper relay locks on. I put the MPU/driver into an Eight Ball Champ with the same result, so I'm convinced it's a board issue. I swapped the PIA's with no change. I can easily replace the 74154, which is not socketed, but I'm wondering if anyone else has experienced and resolved this before I go replacing chips. I know I can whip out the logic probe and start testing the outputs from the 74154, and I will do that with Leon's test rom, if I need to.

I contacted the OP of this thread and he says he hasn't fixed his board yet because his game is working fine with another board.