I posted this in the JP premium/LE owners thread and it has solved some of their their T-Rex issues.
Just wanted to post this here as it may help some of you who are also having problems with the T-Rex not grabbing the ball consistently.
First of all, I did the mechanical adjustments that were listed previously in this thread by Keith and other posters regarding proper alignment of the T-rex. I ensured that when the T-rex opened his mouth that his jaw was resting lightly on the ramp and adjusted the T-rex left and right bias to make her jaw line up with the middle of the ramp. However, she still only grabbed the ball about 20% of the time. The other times it would just go in her mouth come back out and not even start the event. This made me realize that she was not being activated to grab the ball.
I went into switch mode and tested the opto on the trex ramp. it would trigger only if I placed a pinball directly on the ramp. If i raised the pinball even 1/8th of an inch off the ramp the the opto would disengage. I then tested the opto in the "O" lane. I could raise the ball 1/4 to 1/2 and inch and the opto would still be engaged. so with this information I realized I needed to raise the optics on the ramp because my pinball was jumping over the opto 70% of the time. However, there was no easy way to raise the opto as it is attached directly to the ramp. At this point I called Chaz at Stern, explained the problem, and asked if he knew of a way to raise these optics. He did not and suggested write a email and send pictures so he could forward to engineering.
However, once I got off the phone and realized there was not going to be an easy way to raise the optics, I started to think of other solutions. What I came up with is not elegant, but it works.
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I covered the bottom half of the opto with tape.(see tape on ramp in the pictures below). This effectively raised the optics without physically moving it.
Now when in switch mode, i could raise the ball about 1/4 to half an inch off the ramp and the opto would still engage.
I then tested in game. Now, once the Trex opens her mouth to start a Trex mode, 100% of the shots to the ramp are recognized(starting the Trex event) and she grabs the ball about 90% of the time.
This is obviously not a permanent solution, but will work until I think of something else or Stern gets back to me.
hope this helps!