I need to be reeeally careful with troubleshooting here -- considering it was perfect before, I need to be careful I dont make it worse and head into a downward spiral of making things worse!

The mod is from this very thread, see https://pinside.com/pinball/forum/topic/jurassic-park-club/page/141#post-5208312

I put only the top teeth in. Withe bottom in mine had alot of issues eating the ball.

I wonder if adjusting the T-REX assembly under the playfield where it mounts will help him aim for the ball better. (just a wild guess)

Also, the T-REX jaw has a hole in the side where the shaft that closes the jaw hooks on. The hole there was worn on mine, so I put a small tie wrap through and around the top of the hole, so the jaw could close tighter and reliably swallow the ball.

If we're thinking of the same thing, I'd noticed a pin & hole joint on that armature that seemed to have some slop in it. That's a really good idea.

My mech was perfect too. When I modded mine from the stock head, it took me days of messing around with the tabs to get it right. You are moving the tabs inward, making the space for the ball to enter smaller. Opening the tabs makes it larger. Just make sure it doesnt gouge your playfield.

I like the suggestion to take out the bottom teeth. OR you could bend the bottom tabs out.

Also, watch this video. You will be a master at disassembling and reassembling the head. Dont be intimidated. There isnt much to it. Just be careful, go slow, and TEST TEST TEST with your hands, not the game on.:

I don't know if the stock jaw plastic allows the tabs to be bent out much, if at all. The lip is pretty tall. Assuming the rivet and plastic remain in place while attempting the tab bending, there's a risk of damage to the plastic (i.e. even if there's room to bend it, can you get pliers in between the tab and plastic?).

Ya, you're right. He may have to shave the tabs down to get those teeth to work. They seem real thick.

I think the tabs may look like they protrude more because of some of the heating/reshaping I had to to do the snout to get it to fit (per Mr Tantrum's installation instructions) ... since the snout 'widened' slightly in the front, I think that pulled that area back from the tabs a little. In other words, the tabs didn't change (unless I somehow inadvertantly bent them). As such, before I start manipulating/bending things, I'm going to look at that armature pin hole first -- the slop in that pin joint makes sense as a probable cause ... because when he does pick it up, the lower jaw does appear to open fully as he bends down. The lower jaw looks like it doesn't fully open on his way down, on the cycles when he doesn't pick it up. The intermittent/inconsistent nature of it could indict the slop too.

The only contradiction to the pin slop as a probable cause is, why it never had any problems before I messed with it. Perhaps there was already something jammed in the hole and I knocked it loose.

More to follow when I get a chance to troubleshoot it. I've been wrapped up in other projects lately -- getting stuff put together for Chicago Pinball Expo, Free Play Florida, my new website & Pinside shop, etc. Oh, and my day job and family too. lol

The ball gets stuck on the left in lane. I thought the rubber is supposed to sit so part is behind that piece of metal. But it rolls out easily, or ends up popping out after the sling shot fires.

Any ideas?

20201008_150954 (resized).jpg

On mine/originaly there was a metal post instead of the transparent star post
If the ball hangs on the rubber try pulling the rubber more tight and it wil probably help then, or replace the star post for a original metal post.
You can start by trying to place the rubber higher on the top of the star post.

Just go a size smaller on the rubber. Thats what I did on mine. The chart isn't accurate to begin with. It lists rubbers that were never installed on the final game. (up around the Trex). So I took that as any other rubbers listed could be wrong.

I kinda wish the guy who bought the NOS did a teardown and cataloged all the rubbers.

Its worth pulling out the black and putting in clear if your going to make a change. Love how it let's a bit more light out.

Hey guys. I'm thinking of moving a Color DMD LCD from one of my Stern games into my JP. I realize some speaker panel modifications are needed to make it fit, so Color DMD only recommends using the LED version. Does anyone know if I would need to order the Data East Power Adapter from Color DMD to make it work? Or is that only for the LED version?
https://shop.colordmd.com/data-east-power-adapter/

Thanks!

You will need it if you are going to pull power from the board.

Would appreciate help with an non-compliant Trex who won't say "NO". Says "yes" properly meaning his head moves up and down and eats the ball fine. But... left-right movement was disabled by previous owner/seller who told me it was to "keep the motor assembly from wearing out cause it's so expensive." Not true: when I enable the left/right movement the beast creeps slowly left --actually beyond the left limit switch-- and jams/freezes there. I ordered and replaced all of the limit switches and diodes with zero change. Checked motor assembly left-right movement: works nicely, free and mechanically sound. I recall reading about similar left-right Trex issues in this club forum but this one seems different. Could the culprit be a transistor? Maybe Q24 or Q27? I realize this is not a "tournament-critical" function, but it's really nagging me. Any help is welcome.

At first step, check the relays: look for cold solder, stucked contacts. One relay is responsible for left-right movement change.

3a8a169870a1b44f40076a2fb0f43a3ac0b19ade (resized).jpg

I copied the parts for my JP many years ago...
Note:
1) Posts OEM for sling shot kickers Jewel post clr 550-5034-01 ( 3 ) per each kicker.= 6 total.
2) Rubber ring for kicker 2 1/2" black 545-5348-09 ( 1 ) per each kicker. = 2 total.

Thanks Davi. I will definitely check that relay. If reflowing the solder doesn't change anything, I will order a new relay.

Thanks.
I thought sling shot rubbers were standardised for some reason.

This can also be a bad transistor that drives the relay. One transistor makes it go one way and another makes it go the other way, so if one is locked on, you're stuck going that direction regardless of limit switches. However, if turning off the setting keeps it from moving, this may not be your issue. It's been a while since I looked at the schematics, so I don't have any specific parts to say you should check, but the schematics show which transistors control left/right on the relay. It's at least worth a check with a multimeter.

For the record, mine was behaving like this when I got it, but it happened all the time. As soon as the game was powered on the t-rex was grinding its gears to one side. It was a transistor in my case. I never experimented with turning off left/right movement so I can't say for sure if that would or would not have stopped the movement in spite of the bad transistor.

Thanks for your insights winteriscoming. I’ll check the schematic to find our which transistor controls left/right movement and test the suspect. I ordered a new relay for the relay board just in case a transistor is not the culprit. I’ll be back.

I had a bad relay in mine, easy to desolder and replace.

How did you determine it was bad? I’m hoping that’s the case with mine, too. Yes, an easy fix. Thanks.

BTW winteriscoming, if the transistor(s) that controls that relay board is at fault, I’m having difficulty identifying which transistor(s). I’m new to SS schematics (10 years of EMs) but I did find that switches 30 and 31 control left/right trex head movement. Having trouble navigating further. Any help would be most appreciated. I suspect it’s Q27 from past posts — e.g. mr_tantrum’s case — but I can’t verify. I can see where they are all mounted on the CPU. BTW, my CPU is stock DE, his was Rottendog — so configurations and components are different.) I’m adding a handful of TP122/TP102 to my next Pinballlife order to have on hand just in case. Cheers.

I pulled the relay board and checked the relay. Zero ohms. I found a spare unit on the old power supply board, tested ok and scavenged it. Replaced the bad one. Trex now says “no”, so it was in fact the relay and it does work. Thanks again for the tip. The head now turns left to right in both play and test modes, but... verrrry slowly. I can’t tell if this is normal or if the gearbox needs a cleaning and overhaul, or maybe a low voltage issue at the motor? Might there be a link to a video showing how the head is supposed to move left-right?

I spent A LOT of time getting it to work proper, this is what I would do.

Unplug the whole assembly and remove from playfield. Make sure the front bushing is not dragging in its trough. Also make sure the bushing pin is not dragging on cover plate. Clean everything well, light coat of winch superlube on bushing track. Shimmed motor on mine with washer so less force is on bushing to trough interface. Make sure all shaker board fuses and diodes are working (power for t-rex flows through board) make sure no cracked pins at relay board. Make sure motor has good disc caps which smooth out power.

Good points. Before investing the time in taking out the whole assembly, I decided to check operation with a 9 V battery directly to the motor leads. Good thing I did. Worked like a charm. All related left-right mechanisms move flawlessly: fast and smooth. So it has to be a resistance issue where there is not enough power getting to the motor. It's not a mechanical issue. I am now going through every connection that I can find that is involved with this complex circuit. Relay and shaker motor boards check out fine. This will take awhile. Always open to suggestions. Thanks!

The middle scoop switch is the bane of my life.
I've adjusted the switch so many times to try get it to be consistent.
Probably 95% consistent now

What solutions are there to ensure it always activates?

Replaced mine once, never had a problem again

The motor does not run off 9v, that is an error in the diagram. Actually runs off half wave rectified which is about 4.5-5.0 volts.

It will run very fast at 9 volts but its wrong, the motor spec is 5 volts.

I have been through the wringer on this one.

See post: https://pinside.com/pinball/forum/topic/de-jurassic-park-refurb-for-my-army-son#post-5661892

Gdonovan: Yikes. I wish I’d read your log before I even reached for my dmm. Thanks for the link. You’ve had quite a journey with remarkable problem-solving and results. I don’t have nearly the issues with JP that you’ve had, which is intimidating for me. Like waiting for the other shoe to drop as my pin ages. I’m disabling trex side to side movement for now. I don’t want to mess anything up. So much to learn.

BTW, I missed what flipper issue drove you to service the flipper board. My flippers are one of the few finicky aspects of operation. They stop working sometimes, like they have a mind of their own. Mechanisms and eos switches are all fitted and adjusted nicely. I’ve ordered new button switches in hopes they are the culprits. Any caveats or advice here? Again, thanks.

There is a technical service bulletin that covers a modification to the flipper board to fix the flipper drop out problem.

My flipper board had been hacked up pretty bad, made sense at the time to replace. I have the hacked original in my repair pile and might take poke at it this winter along with a few other pieces.

52f492bea4eb99a6d9794e0ddd31673843b04af1 (resized).jpg

My flippers just started acting up as well. Machine gunning, dropping out when held. I have JP on my list to crack open for some maintenance.

Why dont they have the service bulletins on IPDB? Seems like an obvious thing to do.

http://arcarc.xmission.com/Pinball/Stern%20Service%20Bulletins/bulletins.htm

I think it is number 54, covers flipper dropping out due to EOS issues. I have one DE game that will randomly drop out a flipper and I'm going to do this mod. New switch and in 10 games will get dirty and act up again.

Cleaning restores function but 10 games later more or less acts up again. The other side functions perfect.

You can verify its the EOS circuit by putting a jumper across the switch and see if problem goes away, careful not to hold the flipper button in.

Thanks! LOL, I didnt click that link because it says STERN. He needs to work on his search engine optimization.

Its a great resource for Data East bulletins.

Might want to try resoldering the diode on that switch. Three times already, I've had that switch get intermittent and then stop completely -- twice it was the diode coming loose, and one time it was the wire itself. (I need to just remove all the solder from that joint and start fresh, lol)

Do you guys have original DE boards or rottendogs? I had an issue with the rottendog and can help if you're in the same boat.

I need to do a touch-up on the inside of my cabinet. What type of black paint to use? Any particular techniques to be aware of?

https://pinside.com/pinball/forum/topic/de-jurassic-park-refurb-for-my-army-son#post-5678876

I used a satin/matte finish on mine.

I too have had flipper issues lately. I have a Rottendog board (need to send the original board off for a full rebuild). After about 45 minutes of play, it starts randomly not activating and the coils are really hot. I have checked everything, solder joints, EOS switch gaps, etc and haven't come up with anythiing obvious. I also did a complete flipper rebuild kit 3 or so months ago so the components are new.

Great stuff! Thanks for the new link! I'll be doing that mod as well -- the instructions seem pretty clear. Ordered a few parts this morning. I also made a hard copy of #54 service bulletin to add to my manual and will comb thru the list on the link to determine how many others apply to DE/JP.

Thanks. Would you happen to know if this is the original style? I just want to do a touch-up, not a full repaint.

Check your Q1/Q2/Q3 transistors. They should be 2n3906. If it is anything else, you're in for a lot of inconsistent issues. That sad part here is that the issue seems to exist randomly on rottendog boards for more than 7 years.

More info here: https://pinside.com/pinball/forum/topic/rottendog-flp023-data-east-flipper-board-issue#post-5768543

original is a satin/matte finish which touch ups might stick out. Really took no time at all to pull playfield out (the harness is very long and designed for it) and to mask and shoot.

http://arcarc.xmission.com/Pinball/Stern%20Service%20Bulletins/bulletins.htm
I think it is number 54, covers flipper dropping out due to EOS issues. I have one DE game that will randomly drop out a flipper and I'm going to do this mod. New switch and in 10 games will get dirty and act up again.
Cleaning restores function but 10 games later more or less acts up again. The other side functions perfect.
You can verify its the EOS circuit by putting a jumper across the switch and see if problem goes away, careful not to hold the flipper button in.</blockquote

gdonavan: Although I'm sure you most likely knew this, I went through the list of every service bulletin in your link, and lo and behold #42 dated June 22 1993 addresses left-right trex gear box premature failure, which was due to "excessive speed". This was corrected by version 5.00 program that "provides a more intelligent speed control to help slow it down prior to limit switch closure." (There was no "attached diagram" included for limit switch modification/adjustment.) Because my serial number post-dates the one noted in the bulletin, and because I replaced the bad motor control coil, the trex's head is probably moving at the reduced left-right speed and force. So I guess this issue is resolved. Moving on to flipper board mod #54.

gdonovan: I went through the list of service bulletins you posted and found more than a dozen with relevancy to DE JP. Lo and behold, there is one that answered my previous post relative to why trex struggles with left-right movement and why it moved so fast when 9 VDC was applied. #42 explains that version 5 program kit deliberately slows the motor speed to prevent shock damage to the gearbox. Says it "provides a more intelligent speed control to help slow it down prior to the limits switch closure." Changes affect serial numbers after *87177, which is well before mine. But you probably knew this. Issue resolved.

Try reading technical service bulletin #43 - it discusses your issue with switch #37. It states: "Cause: broken diode on center scoop switch. Replace broken diode. To prevent shock damage to the diode apply a silicon rubber compound to the points where the diode is formed to absorb the impact." Good luck.

Does anyone have a lead on a great condition PF? Great to me means little to no scoop wear and good oranges/reds

Does anyone need a new left ramp? Never used, also have good trex motor and gearbox. Make fair offer. Ill list it here so pinside gets their cut, if anyone needs. Thx