Data East's Jurassic Park is a pinball machine I had been interested in owning for 15 years!
Jurassic Park is based on a groundbreaking film from the 1993, has integrated the theme well, and has a great playfield layout. It's just a lot of fun.
Regarding the playfield layout, I need to paraphrase what a couple of friends told me. "Data East Jurassic Park is the best Pat Lawlor machine that Pat Lawlor didn't make." Put another way, DE borrowed liberally of Pat's design chest. To be blunt, there are a lot of similarities between Jurassic Park at Adams Family that one can only chalk up to lots of "borrowing" by DE.
Oh. Did I mention the T-Rex that eats pinballs? That is truly awesome.
I'm just getting started here. Below are a few topics I should write about...
Original February 26, 2018
Data East pinball machines are known for having speaker hum. People often speak generally about the hum from these machines. It is, however, typically generated by 1 of 3 causes.
The hum / buzz from DMD and light effects can be eliminated by (1) disconnecting the power cable that goes to the DMD and (2) entering diagnostic mode. The first, well, disables the DMD from displaying any content. The second places the game into diagnostic mode where it doesn't perform any light shows.
I noticed that the constant hum / buzz was not impacted by the volume setting. Specifically, I could turn the volume up or down and the hum would not get any louder or softer. This strongly suggests the hum / buzz is being introduced after the volume circuity.
Using an app on my phone, I was able to determine that the major hum / buzz cause was a 120 Hz sound at about 58 dB. Using a scope, I could see this in the 12 VDC signal going to the sound board. With my XPIN DE5047 after market power board, I measured a 1.3 VAC 120 Hz ripple on the DC line.
A 120 Hz ripple is a signature of a full wave bridge rectifier. Briefly, a full wave bridge rectifier takes a 60 Hz AC source (at least in North America) and converts it to DC. The negative portion of the 60 Hz wave form is made "positive", resulting in a 2x frequency change. Hence, 60 Hz becomes 120 Hz. This ripple is typically reduced by the use of a smoothing capacitor.
The XPIN DE5047 has a 10,000 uF cap. The original Data East power board using 18,000 uF cap. To see if this was part of the problem, I added 15,000 uF in parallel to the existing 10,000 uF. With this configuration, the ripple was reduced to about 500 mV. However, the audio hum / buzz wasn't significantly impacted. I added additional capacitance but was never able to get the ripple any lower. I still don't completely understand this observed behavior. One theory is that the power board cannot provide enough current to charge my caps fast enough and, as a result, they cannot smooth ripple further. That's just a theory.
I also replaced several caps on the sound board. It's not uncommon for caps to behave poorly with age. I replaced C31 / C52 (with upgraded 1000 uF) and C60 / C67 / C74 (with 470 uF). This had no impact ... or, perhaps, seemed to make the hum a little worse!
I had read that some people had good results by powering the sound board with an external power supply. While I feel this is a bit of a hack, I decided to give it a try. If nothing else, it would let me know whether the sound board was capable of producing audio without hum. I did the following:
The picture below shows the wire splices done to the ATX power output. I only had red wire so, unfortunately, all 4 wires are red.
This picture below shows the splice between the Data East 120 VAC lines and the ATX power cable. The "service" plug on the Data East pinball cannot be used because it isn't switched on and off along with the game. Rather, it provides power all the time.
This picture below shows the connector that was built and plugs into the sound board's power input.
Finally, the image below shows that ATX power supply. I drilled 2 holes into metal L-brackets at the right position to allow screws to hold the ATX supply in place. The ATX supply is also connected to the ground braid.
In conclusion, I feel using an external power supply is a bit of a hack. However, as far as hacks go, I feel I've performed this one in a fairly professional manner. I'm still interested in resolving the hum without an external power supply, but this approach will hold me over until I decide to peruse the analysis further.
Bally/Williams Pinball machines from (at least) the 1990s had 2 small holes in the playfield that could be used to ensure the flipper resting position is correct. The technician would placea toothpick in the hole and then let the bottom of the flipper rest on the toothpick. Very simple.
Data East also placed 2 small holes in the playfield, but not in a position where a toothpick could be used (at least starting with Lethal Weapon). Rather, the technical needed to "eyeball" the center of the flipper to the hole. It's not too uncommon to see Data East pins with flippers aligned incorrectly. The wrong alignment has a significant impact on the gameplay.
Service Bulletin 108 describes the proper alignment. The key figure is captured and shown below. Oh, I'm writing all this because the flippers on my Jurassic Park were not aligned correctly and the game played significantly better once the alignment was corrected.
It had clearly been a very long time since anyone took Jurassic Park's subway off the bottom of the playfield and cleaned it. Below is the before (dirty) picture and the after (clean) picture.
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