Actually handy for me to find this link because I recently acquired a Playboy which I think uses the same board .
The Stern soundboard is totally different to the Bally board Dave
![yes *%*](http://www.aussiepinball.com.au/Smileys/classic/yes.gif)
As Dave suggests though the fault could be one of the 4013 ICs causing the problems with this particular board.
I just had a look at the schematic for this board.. I'd say U9, judging from the voltages quoted for TP2 and TP5 in Sinbad79s post above, would be a good place to start.