Ok well it's not the optos it's a voltage issue when the boards are unplugged there is no voltage so it's dragging earth from the board.  When I connected an earth straight from the cabinet to the pin the balls began to feed but only or a few second then it started to slow down then stop grrrrrrr

  Does anyone have an original manual for rapid fire?  The online version is unreadable in the section I need (what a shock).    I've tried following the the cables but it's a nightmare under there of I can work out where it draws it's power I'll run some new wires to rule out damaged wires (highly possible in that mess