(Topic ID: 414)

Non-Mechanical Issue on Jurassic Park T-Rex??

By ccwright

14 years ago



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#1 14 years ago

I have been getting a high level education on pinball repair during the past few weeks, after purchasing and shopping a Jurassic Park Data East Pinball (1993). This is the first Pinball we've ever owned...

When I do encounter an issue, in addition to combing thru the manual and online repair guides, I also like to post here in case anyone has seen this before (or to help others in future who encounter same symptoms)...

- Issue is with the T-Rex (supposed to eat the ball from saucer on playfield)
- Appears to be working fine mechanically
- Passes start-up diagnostics, and during manual diagnostics I can control all three motions (left/right, up/down, mouth open/close) with no issues
- Two weeks ago, was picking ball up fine and swallowing, just as designed. Turns L/R, bends down, closes mouth over ball, bends up, chomps and swallows ball.
- For unknown reason, it now bends down, closes mouth on ball, then opens mouth before going up again (which means it cannot hold onto ball) and then chomps as normal with empty mouth.

What confuses me is that TRex appears to be functioning fine, for the motor and coils, and the behavior is new (was working fine before) without apparent known cause.

What am I missing? My first thought is that it must be software code problem if not mechanical, but I don't understand how that could be if there has been no change in code.

Any ideas??

#2 14 years ago

Im not to familiar with how the Trex mechanism works - but sounds like there could be a switch or other sensor stuck or not working properly to tell the T-rex where it is in its cycle to pick up the ball. I saw somewhere else that people have disable the left and right movements fo there trex and just have it go up and down to get the ball. that is in the adjustments menu. But if all the left right up down work, seems like its a sensor of some sort that dictates his next action. Let us know what happends - I havent played that game in years - but I remeber something similar happening in a few games I had played, not sure if that was part of the game, but it would pick it up sometimes and leave it as you mention

#3 14 years ago

PROBLEM SOLVED!

Just FYI - after doing more troubleshooting and taking apart the top TRex mount and assembly I found that the wire feeding the coil for the TRex jaw had been previously repaired and wrapped with tape. I unwrapped and discovered that the connection to this coil was intermittently working loose as the TRex head moved thru the 10-45 degree angle of its arc (opening jaws and dropping ball).

I respliced the repair and re-assembled the mount and found that problem was solved. Now on to next item on my repair list...

2 years later
#4 11 years ago

I just dug this up to add to it. I discovered the same problem with my t-rex that had stopped grabbing the ball.

My symptom was that the t-rex was chomping too late almost as his head was back upright. Initially I thought that the up/down switches were playing up but after removing and cleaning those nothing changed so I figured it was a wiring issue like ccwright had above and checked it out.

The best way to test if it is actually wiring is to put the machine in t-rex diagnostic mode and, while holding START to cycle the down/up motion, repeatedly pull the launch trigger to chomp his jaw. In my case the jaw stopped responding as he dropped lower than 45º and started responding again as he reached the same point on the way up so I knew there must have been a connection breaking at that point.

Best thing to do from there is to leave the t-rex lowered for easy access to the screw at the back of his head and visibility of the assembly. Remove the main head plastic and you can get a good view of a large shielded wire running from the base of the coil around the back of the assembly and under the play field. In my case this wire had fatigue split right where it goes through a 180º bend on the right hand side. When he's raised up this bend is squashed by the rex's plastic neck piece and eventually this split it.

The best remedy I feel is to replace this entire shielded wire altogether. I just cut and spliced it together for now but will replace the wire in the long-term.

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