I wanted to start this topic so it wasn't buried in the owners thread.

I just received a NIB Jurassic Park Premium last week that I had ordered at the end of June. It was a July 19 build. While this is not my first pinball, it is my first Stern (coincidently, we got an IMDN a couple days before this arrived. JP3 is still technically our first Stern). I've been repairing machines for a few years now. So, I know my way around them pretty well. I researched JP for awhile to know what to expect when I got it. I have read all the Pinside forum posts on the subject of the t-rex mech. I've gone through all the key topics. I adjusted the biases and checked the wiring. I've seen the PDF's. I've read Keith's posts. It came with version 1.02 already installed, but I reloaded it anyway. I've reset everything to factory defaults.

The problem is the t-rex seems to forget where its center is sometimes. I have tracked the problem to most often occur after the t-rex throws the ball in "RAMPAGE". It will turn its head directly over the left wire form thinking it's in center position. During that event, it pushes its head down on the wire form instead of centering and lowering on the ramp which kind of indicated to me its not a bias issue since that adjustment is for minute changes even though I have the right bias now set at -7. It will continue this malfunction until the game has ended. Upon starting a new game, the head will correct itself and function properly until after the next throwing ball or RAMPAGE session then the problem occurs again. The only solution that I have gotten to work, for the most part, is to turn off "throw the ball". However, it will still occasionally error with this setting off. I also unplugged and reseated all the connectors to the t-rex head, checked for free motion in the back. All wires move freely. I checked the micro switches to see if maybe it might be losing the signal to know where it is. They all test good.

I contacted Stern and after the initial reply trying to get me to do things I already tried, I sent them this video. They replied that the engineering department has determined that it is a mechanical failure and not software. If no one else has had this problem in the code I will be inclined to agree its mechanical. Maybe the motor is overheating? They are sending me a new stepper motor on Tuesday to replace the one I have. I will update this thread if that works or not. I'm skeptical this will fix it.

The questions I still have are:
If the micro switch is there to tell the mech where center is, why doesn't it alert or stop the mech from moving up and down when it is so far away from the center?
Could the board on the back of the playfield that the horizontal motor plugs into be faulty as well?

If anyone else has had a similar issue, input would be appreciated.

The video begins at the start of RAMPAGE. The in game sounds are turned down so I could try and hear the mechanics.
:00 T-rex catches the ball and begins the throwing motion. It moves freely left, center, and right.
:20 The t-rex now thinks center position is over the wire form. It will only move to the left as far as the center ramp.
:42 The head pushes down on the wireform trying to open its jaw.
3:22 the t-rex resets itself at the start of a new game.

The replacement stepper motor arrived today. Let me start by saying, as I suspected, replacing the stepper motor did NOT solve my problem. However, one day this information may be useful to someone. Here is a step by step of removing and replacing the stepper motor on the t-rex:

1. Get the obvious things out of the way. Turn off/unplug the machine. If it was just played wait until the mech has cooled down before removing it.
2. Carefully lift out the playfield far enough to easily reach behind the t-rex.
3. Unplug all connectors. This includes all the obvious wiring coming though the neck of the t-rex, plus one microswitch harnesses for the horizontal and the harness for the three vertical microswitches (The vertical harness is underneath the mech.), the wiring harness for the stepper motor on the STEPPER MOTOR DRIVER BOARD (CN2) and the harness on the SERIAL MOTOR DRIVER BOARD (CN2) below it connected to the gearhead motor.
4. Photograph or mark where the bottom plate is positioned then remove the bottom two nylon lock nuts on the lower plate. Loosen the top two nuts. Do not remove them. It will be easier to reinstall later. The bottom part may now swing free.
5: Remove the four screws from the top plate.
6. Carefully, while supporting the entire mech lift it up and around the ramp. Avoid letting the bottom part hang on the plastic arm alone.
7. On the bench, remove the outer heat shield.
8. Rest the t-rex on the top of her head and place the lower motor up on top.
9. Turn the head so that the allen set screw is accessible. Loosen the screw to free the shaft. Remove the four screws holding the motor on. The replacement motor came with a new crank assembly, (EDIT: USE THE NEW CAM ON THE NEW MOTOR. DO NOT USE THE OLD ONE.)
10. (EDIT: THIS STEP SHOULD BE SKIPPED THE NEW MOTORS DON'T NEED IT.) There should be a metal washer on the old stepper motor. Put it on the new one.
11. Start reversing your steps by first adding some thread lock to the four screws and then positioning the new motor in place. Screw it in.
12. Make sure the crank assembly is rotated in the correct position to allow it to activate the microswitch as the head reaches center. Lock down the set screw when you've got it. Move the head slowly back and forth to make sure it moves free. If you try to move it too far in the left position it may lock up the plastic arm. In the game it never moves this far left so it isn't a problem. Just gently turn it center before reinstalling.
13. ***OPTIONAL STEP***: I noticed my lower motor the gear head motor had a bad soldering connection on the casing and wasn't actually attached just touching. This isn't an easily visible point to see when it is on the machine. You can see it if the playfield is in the upright position though. I resoldered it. I'm not sure if everyones motor is like this, but check the soldering on this.
14. Reinstall in the machine, reversing your steps, paying close attention to getting all the wiring harnesses plugged back in, and the position of the lower plate back to where it should be. This affects the jaw position. For me, the bottom edge of the plate was rests on the playfield. Tighten the lock nuts back down, if you know you've got it back in position, otherwise you may have to go through the steps in the Stern PDF on positioning.
15. Once it's all in like it was, turn on the machine and go through the diagnostics and bias settings to realign your t-rex.

Hopefully, your t-rex will now work properly. Mine still has the same problem as before in my video where it loses its center and pushes on the wireform until a reset. I'll be contacting Stern again. My questions for them will be as stated before:

1. If the microswitch for the horizontal position center is working properly as mine is all the way to CN13 on node board 9, why doesn't the system know that the head is not centered and stop it from moving vertically down?

2. If the problem is not the motor or microswitch, doesn't the problem have to lie somewhere in this path. Stepper Motor Driver Board>Node 9>CPU Node Board>Game Code?

I have conquered Dracula's pain in the butt Mist Multiball repair, Johnny Mnemonics twitchy glove, I will not be defeated by a t-rex.

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I have tested the micro switch with a meter and it’s tested fine every which way I try to trigger it. If, in the end, it comes down to being that, I’d be surprised. I’d be thankful, but surprised.

Thanks, I get where your coming from. The head only has one micro switch for horizontal movement. It closes when the head is center and is open the other two directions. There’s really not much to it. You can see it in one of my photos above. The driver board tells the motor which way to go left or right but the micro switch is only to identify center. Tomorrow, I’ll change it out anyway to absolutely rule it out, but I have an email in to Stern regardless.

From Stern after reviewing this thread:

“Engineering came back to me and they are telling me that the original motor is an early run and early run assemblies have a Washer installed between the Cam and the motor. The motor assembly I sent you had a cam on it that I also sent. Please remove the Washer and make sure you install the new cam I sent you and let us know if this takes care of the issue. The replacement motor/cam I sent does not need the washer installed on it.“

I will take it apart again today and do what they suggest to see if this works. Stay tuned.

Okay. Still NOT working, but I did what was asked of me by Stern and once again removed the t-rex. (Which went a lot faster the second time.) I replaced the old cam with the new one that came with the new motor. You can see a difference between them in my photo below that I hadn't noticed before. (LEFT new RIGHT old). I eliminated the washer. The pivot screw needs thread lock so don't forget to put that on before reinstalling. Put it all back together with the same result which I will post a new video in the next comment after this one.

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This is an updated video I took today after I swapped out the cam and removed the washer.

Setting up the video:
Glass is off.
Sound is turned down.
"Throw Ball Enabled" is turned on.
The video starts shortly after ball launch as I manually hit the truck to start Multiball. After I let the multiball drain, I, again, manually advance the truck to the RAMPAGE event.
The exact same problem occurs in RAMPAGE at the same time it did in my previous video.

I should also note that if "Throw Ball Enabled" is turned off RAMPAGE functions normally, but there is sometimes, not all the time, a slight glitch during ENCOUNTER where the lower jaw gets hung up momentarily on the wire form after the t-rex roars because it didn't lift its head up ever so slightly like its supposed to or does most of the time. This may still be fixed by a bias adjustment, so it is not my main concern.

(Sorry, no tripod this time.)

Sent the new video link to Stern. Became late in the day, so I’m not expecting a reply for awhile.

I’m not an engineer and I’m sure they’re doing their best to find a solution for me amongst all the other things they must have going on, but I am a thinker and a problem solver especially when it comes to malfunctioning arcade and pinball machines. I love the “thrill of the hunt” tracking down bugs and glitches getting old machines to work again. Just didn’t think I would be working on a new one so soon. I fully expect to be a t-rex expert by the end of this.

It is interesting to me that by turning off “Throw Ball Enabled” it doesn’t have the issue anywhere near as often. The neck still thrashes around in certain modes, but for some reason maybe because it doesn’t throw the ball it’s able to recover better. I don’t know. My gut is still telling me it’s the Stepper Driver Board if not a code issue.

I hope that whatever the solution to my t-rex issues end up being will help bulletproof what is an otherwise awesome game...that I still suck at playing.

But it’s only if the adjustment setting “Throw Ball Enabled” is on though. If it is off, it can swing its head just as fast back and forth and still work. That’s what’s weird to me. I’ve tested the wiring from the switch all the way to CN13 on Node 9 and it has good continuity.

No problem. I know I wouldn’t have been able to fix my other machines without help from this forum, so it’s only natural I return the favor.

Since I'm still waiting for a response from Stern, I decided to conduct a few tests. I wanted to see what would happen during a cold start up with "Throw Ball Enabled" OFF vs. a cold start up with "Throw ball Enabled" ON. I did the first test then shut down the machine and allowed it to cool off completely then repeated the same steps with the other setting.

The first test is Throw Ball OFF. Multiball straight to RAMPAGE. Cold Start. Room Temp 77º. No Error.

The second test is Throw Ball ON. Multiball straight to RAMPAGE. Cold Start. Room Temp 77º. Error begins at a later point then previously seen. At 4:09 there is a sound I hadn't heard before (Possibly the vertical motor still running or I hit the Raptor gate?) right before the error begins. (Ignore me having trouble getting the ball up the ramp with my hand. I know I suck.)

Immediately after the second test, I lifted the playfield and inspected the back. There is heat coming off the motor housing. That is to be expected. There was also heat on the Stepper Motor Driver Board at location L1 (see photo below). I suspect that is normal too. However, I'm starting to think that maybe heat is playing a factor in the error since after doing this test I got further in the mode before the error occurred than in my previous videos where the machine had been on for a time. So now my gut is saying that the when the Stepper Motor Driver Board heats up it reveals its fault. I won't know for sure unless I can get a replacement board to confirm it.

I also did another test with a camera behind the playfield focused just on the Stepper Driver Board. There are two orange LED's on it and I wanted to see if there was a visible difference when the error occurred. The LED's stayed on the entire time, so I haven't included that video.
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Okay, this is where we are at.

Stern sent me an email based upon my latest post:

"Looking at your video Clips I noticed some Nice Art blades on your game! Can I ask were those were purchased or the Manufacture? Also, Try Disconnecting the Art blades and let see if your error goes away. We are wondering if the Extra Lighting is causing the issue whit it shutting down and getting Hot."

To which I replied:

"They are pingraffix powerblades. They use EL wire and don’t generate heat. I only recently installed them and the error was present BEFORE they were ever installed. The very first video I posted is before the powerblades were purchased. Also note that the glass is off in the newer videos. I am certain they are not the issue. If you would like me to make another video with them unplugged though, I will."

Stern:

"Try disconnecting them and perform a factory reset."

Which brings us here. This is a real time video. Disconnecting the Powerblades (Which only connect to the aux power, nowhere else.) Turning on the game from a cold start. Performing a factory reset. Starting a game just like before Multiball to RAMPAGE. Room temp is now 75º.

I hope I’m the only one that ever has this problem. I hope it’s a fluke and not indicative of a bigger issue. But the information I’m providing and working through will be a great help down the road as these machines start to age. Granted mine is only one month old at this point, but I hope to have it for decades. Better to work out the bugs now.

Since Stern has probably gone home for the weekend and won’t get back to me until next week, just as a point of note, I have had my machine on for almost 4 consecutive hours tonight and the Powerblades are still cool to the touch as when I just turned them on as is its controller that sits in the bottom of the cabinet near the back.

Plus, I have played many games tonight with the “Throw the Ball” OFF without an error, until the one time I turned “Throw the Ball” ON. I feel this part of my issue is getting lost in the many recommendations to solve my issue.

At least I can still play it.

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The dangers in troubleshooting is completely dismissing things that you believe, at the time, could not possibly be the problem. So this afternoon, to cover all the possibilities, I will be going back over the mechanical aspects of the head and really seeing how it all works together. Maybe, I missed something there.

Okay, I took the t-rex out again and examined the parts. I removed this one arm and cleaned it with isopropyl alcohol. I didn't like the placement of one of the zip ties on the wires coming from the neck (Photo 2 below. In the photo I pulled the wires back through the front to get easier access on the zip tie. THIS IS NOT WHERE IT IS SUPPOSED TO STAY. I pulled it back through after I was finished). I felt that zip may get in the way of free movement in the future as the game gets played, so I moved it away from the arm slightly. I also added another zip tie to bind all the wires together, not tightly, just enough that the wires won't want to lift up and possibly snag the cam as it turns away from the t-rex frame.

SLIGHT BREAKTHROUGH! Still not fixed, but I can now make the error happen on command AND fix itself through the diagnostic settings. Here is a video explaining what I am doing to make it happen.

*NOTE: I made one error in my explanation. If you hit left - or right + to roll through to the other side it doesn’t make a full circle in the motor. It will go back and forth. It only makes a full circle when thrashing.*

(Not sure why the audio doesn't kick in until a few seconds into the video, but all the pertinent information is heard.)

Question is where to go from here....
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Just for testing sake. I disconnected the arm on the back of the neck that connects to the stepper motor and ran the tests again without any resistance from the head. It worked every time.

So, what in the head is pulling the motor off center?

All the parts seem to be there in the proper order.

Is the balance off? Maybe the weight?

That’s because when it is thrashing it is making a full circle rather than just moving just left and right. Thus, the cam is 180° from the center tick but it is still passing center visibly without triggering the micro switch. So basically every other time it passes center the micro switch is activated.

Right now I’m focusing on trying to find ways to alleviate some of the weight and pressure on the cam arm. I already found a spot that could use a washer. It helped, but there is still some pressure on the cam arm at the apex of its turn.

Progress being made. There is this joint in the neck that had a bit too much up and down movement and was putting the cam arm (the little white plastic piece in my earlier photo) out of alignment with the cam. I added a small washer to take up that play and help the arm stay level. There is also a little bit of pressure at the apex of the turn. I’ve been looking over the whole t-rex trying to find places that I can tweak to give the cam arm just a little more slack. So far just one place. If I loosen the six housing screws and push the frame and motor closer to the head it gave me the tiniest slack. The stepper motor itself is cut to fit exact so there isn’t any play there. I just need to find a little more slack somewhere. I have redone the tests and as long as I start the thrashing in center, it will find home, but if I start on the left or the right it loses it again. If I can squeeze out even a hair more, I might have it.

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Thanks,

I assume a ton of other t-rex's are working just fine. This one slipped through the cracks, probably because they just play a quick game on the line and move on. Aside from this, when I got it, the right slingshot wasn't firing. It was a misadjusted switch, no big deal. Hard to notice in a quick game unless you know what you're looking for. Our IMDN had a pop bumper switch the same way and it was only 300 games old when we got it.

That being said, I live in the middle of nowhere. There is no one around that sells or knows how to properly repair arcade or pinball machines. I learned myself. I didn't even think to buy a NIB until I learned how to fix them enough that I felt comfortable doing it myself. I've only been working on them for a little over a year and I've learned a ton, thanks to this forum. Yes, we want them to be trouble free, especially NIB, but I'm a reasonable guy, I get it. There's a lot of little parts that all have to work and then work again after being moved and shipped and in and out of different climates.

I enjoy fixing them, so as much as I didn't expect this big of a problem from a NIB, I'm learning.

Stern has been trying to help me when they can. They are aware of this thread.

If I solve this, I want an engineering credit in the next code update, lol.

Update!
I actually got it to work properly...for two minutes. I have been on a quest to balance, align, and loosen the tension off of the stepper motor caused by the neck and cam arm. I thought I had successfully removed the tension on the cam arm to allow the stepper motor as free movement as possible. When I checked as to why it got stuck again, the adjustment I had made worked itself out from the movement of the head.

So, once again I had the t-rex on the bench. (This makes over ten times now, I think.) The white plastic cam arm needs to be jiggly at every point in its rotation. Mine gets tight at about the seven o-clock position (if the back of the t-rex represents six o'clock). So this time, I once again pushed the frame forward which isn't much, barely moves, and thread locked the six screws on the frame. I'm letting it dry now.

I wish that the plastic cam arm had just a slightly bigger hole on the end over the stepper motor itself or was even a tad longer. I think that would be enough to allow for free movement of the cam arm in the whole rotation, alleviating the pressure on the motor, without having to try to push the frame forward.

I'll check tomorrow. If it works, I'm not going to call it fixed yet. I need to make it a solid repair first that can't work itself free.

Photos below for reference.

I just want to play.
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Email from Stern today:

“Thank you for the update and Sorry you have had these issues with your game. At this point I would like to send you a Complete replacement T-rex assembly for you to swap out on your game....”

So, there we are. I’m still going to put my t-rex back in for now since I can still play the game with the settings changed. When I get the new one in, I will update this thread.

Thanks for following along and hopefully, it helps someone in the future.

It sucks, doesn’t it? I would start going down the list of basic checks because Stern will want to make sure you’ve done that first (bias settings, check for wires getting snagged), but if you can make the error happen in a video and send it to them It will help them see the problem.

It’s supposed to make the steady sound that sounds similar to a ratchet when it moves the head left and right. The motor moves back and forth, but you can hear it skip or pop when thrashing as the motor makes full rotations in that mode and that’s where the problem is.

I think they need a slight redesign to the plastic cam arm to prevent this problem.

I’m still waiting on my replacement. They make you order it through your distributor and not directly from them. So I don’t know when I’ll get it. I have mine set to PRO rules for now.

Update: My replacement t-rex is on backorder which means I probably won’t see it for awhile. They probably have them made on an island somewhere with all the other dinosaurs. I sure hope there’s no typhoons in the area.

It sounds like a stuck switch somewhere. I would go into the switch test in utilities and check to see if any switch is activated that shouldn’t be first. Then go from there.

Default is to have two letters For MAP already lit at the beginning of the game. So one of the white arrow paths is probably where the switch is stuck.

I hope you’re go to go now! I’m still in backorder limbo, so it will be awhile for me.

Sucks. The important parts, IMO, is the positioning and free movement of the cam arm. This would require a complete and correctly built assembly for the horizontal stepper. Whenever I get mine, I’m going to test the movement before I install it.

Yes, it does have the sound issue. It doesn’t bother me as I only really hear it during that test. I was planning on changing out the speakers anyway.

I do not have a shaker....yet.

I haven’t really looked into it yet, but the speakers do look kinda crappy. Could be the equalizer mix for those speakers isn’t right. Idk.

I’ve seen in a Stern video that these kinds of parts are assembled in house. I’m wondering if maybe the new guy put these together one day. It will be interesting if they come out with some updated parts for this based on enough people having the issue.

Shipment notification from Stern today. Next Day Air. Looks like my replacement is on the way....fingers crossed it’s a working one!

I hope so too. It would be completely impractical for me to have my machine replaced as I live nowhere near a distributor. Good luck with yours.