Opto problem
It turns out that the problem reported in my last post regarding the intermittent fault on one pair of optos wasn’t simply solved by cleaning. In fact it didn’t matter how often I cleaned the opto pair, the fault would repeatedly come back – but not permanently. Time to investigate….
On taking the necessary opto apart I was horified to discover a lead which had never been soldered. This means that this pinball machine has had this intermittent fault since its birth:
Source of an intermittent problem