You may be in luck... I was sent a flipperless United game schematic by a very nice gentleman on the Rec.Games.Pinball forum (Larry Wolfe) when I was in the middle of restoring a United Serenade, which was a blast to do, and nice playing game.
Let me take a look at my paperwork file and see what game it's for. May not be the same game, but most of the flipperless United games shared many of the same circuits.
What's the issue with your game?
Don O