Sounds like the switch for that one drop target is stuck. Is it a leaf switch or opto switch? What game/title is it?

It's possible your opto for that target is just dead. Or could be a flaky connector pin

If the opto is dead, then your game doesn't know when that target has been hit. This would not impact the game resetting all three targets. Have you tried it in test mode?

In switch test, does it register any of the drop targets in that bank? Should be switches 27, 28, and 29.

There is no self-trigger for these drop targets, or any of the four drop targets on that game. You must manually trip them to test them.

In your first post, you mentioned that the other two drop targets score points as appropriate. If so, they should work in the switch test. When you go into the switch test are you using your finger to knock the drop targets down?

Physically, that means that the drops themselves are okay, but that does *not* mean that the switches associated with the individual drop targets are working correctly. What I was trying to get across was that there is no self-dropping mechanism (such as a magnet pull) for any of the drop targets in this machine.

To see if the drop target switches are working, go into Switch Test and make sure that the drop targets are all in their full upright position. Push each one down with your finger starting with the ones that you *know* are working correctly. When they go down, you should hear the machine make a noise indicating that it knows the drop target has been triggered...the display should say so as well. When you get to the one that's the problem child, see if the noise is made/machine recognizes that it's down. If you don't get the same behavior as the others, it's most likely the switch issue, which could be with the optos, or the opto board, or the connector.

I hope that that is more clear.

Before you go and do all that, do the simplest thing first: try cleaning both sides of the opto with a q-tip and some cleaner. See if that gets the switch working first. It could be just that simple. Visually inspect it as well. Could some Novus 2 or similar dripped down there or something?

Nice, you've isolated the issue to the one switch. I would replace the opto before buying a whole new board. You could check for continuity from that opto to the interconnect board just to make sure there isn't a broken wire somewhere. Changing the opto is pretty straightforward.

Did you test the opto manually with your finger or something? Perhaps the drop target isn't breaking the opto?

The switch matrix shows which wires are associated with that switch. From this image you see the wire colors and I believe where they connect on the MPU. However, they go through the interconnect board first. Just to make sure there is no break in the wires under the playfield, you can use a multimeter to check continuity from the opto board to where it connects to the circuit boards in the backbox. If you pull the connector off the opto board and off the interconnect board, just touch one lead of the multimeter to each end of the wire in both connectors to see if current flows or if there is a break. I mention this because just recently I had a switch die and it was from a disconnected wire under the playfield.

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Great to hear!

Excellent. Well done. Glad it was just that simple...nothing lasts forever!