I have a VUK opto that isn't working right. It always shows the beam as being blocked, even when it isn't. I tested the receiver opto with a flashlight and it seems to be working fine. I would assume that this means the emitter is bad, but I can see that it's on when I look at it. Two questions:

1) Does it matter if you can see a bright red light coming out of the emitter LED? Should it be only visible with a digital camera?
2) If you can see a bright red light, does that mean that the reciever should be picking up the signal?

It's a Sega Batman Forever.

Do you have an idea what I should try next? The "dark" receiver seems to work fine when I shine a light on it, but nada when the red LED from the emitter board shines on it. Seems like it should work...

I'll give it a try. On a side note, what exactly does the VUK opto do, look for jams? It saw that it was unplugged today and it must have been that way since I got the machine. It seems to be functioning okay without it.

Yes, I get that. What I don't understand is why it kicks balls out despite the opto receiver being unplugged.

When it's unplugged it doesn't kick until there is a ball in there. I assume it's because it knows it just released a ball into the VUK, not because the opto is telling it there is a ball in there. When I plug it in, I guess it starts receiving a signal and thinks the switch is open and starts kicking.