Hi, one of the ball lock optos on my mini-playfield isn't registering in switch edge testing and I'm hoping someone can guide me towards next steps. It's just the left-lock opto. The right-lock opto works and I've been using it as the baseline for diagnosing the issue.

So far I've replaced both the transmitter and receiver and verified that they are functioning. I'm also registering 13.4V, same as the right-lock. So it seems that the optos are operational and have "spark". Where should I look next? If this is a board issue, which one is the likely suspect - CPU or Opto Switch board? And is there a way to tell? From just eyeballing the boards I see nothing remarkable about either one. No corrosion or burn marks on either.

Thanks in advance for your help!

Thanks. I verified by soldering the receiver opto to the right-lock (the working one) and it showed up in the switch edge test.

Pinwiki is such a great resource but I always forget to check it. Appreciate you pointing me in the right direction.

I was able to narrow it down to the opto board thanks to the Pinwiki link. Thanks again.