I've been having problems with my Star Trek Pro Drop target for months now. I've read all of the forums regarding different fixes. My drop target was basically going up and down super fast and then go into Vengeance mode. This would happen when I first start the game and continued to do it throughout the game. Sometimes it would be really bad and other times it would get better after fixing what I thought to be the problem. I've read several forums with different fixes (washers, springs, bending brass lever, pushing drop target assembly back and creating a new plastic bar that goes across). I've tried all of these and none of them worked for me. However, I did find some other forums that helped me and now I believe it's working as it should. I had 3 problems. Every time I thought I fixed it, there was another problem. I am not a pro, but I'm hoping this will help some people.
1st. - I had a bad opto. The opto directly behind the drop target was flickering. So I replaced the 2 (transmit / receive). It's a pain in the neck to get to. You basically have to remove the ship and a portion of the Alpha ramp to get to them. You'll also need to remove some plastic on the right side. I watched a Youtube video of how to straighten the ship and this helped me a little. The drop target worked for awhile and then started going up and down again (Dang It)!
2nd. - I read a forum that said to test the switches and check (I think# 14) the Alpha Ramp. You can check this by putting the machine into switch mode and tapping the Alpha ramp to see if it detects a faulty opto or switch. So mine was dirty and I cleaned it with alcohol and a Q-tip. This worked, but I ended up replacing them anyway. Then, when I put my Alpha ramp back together from the previous fix, it seems that the ramp is spread further apart some how and the optos where not seeing each other as they should. So I needed to squeeze the ramp a little and now that's fixed.
3rd. The game played perfect for a week and then it did it again, but faster. UP DOWN UP DOWN UP DOWN. It was worse! DANG IT! So, the 3rd fix was the coil that activates the drop target mechanism. The coil screw that holds the metal plate (directs plastic drop target up and down) onto the coil, was loose. I put some lock-tite on the screw and tightened it. Now it's working great again, fingers crossed.
Info- I also replaced the plastic drop target, plastic bar and spring before trying these fixes. Something else, I've removed my drop target assembly from the play field so many times, that now one of the screws are starting to strip. So, don't over tighten them.
Shout out to Pinside! These forums really help.