Return of the interlock. Why?

Stern Jurassic Park has an interlock. The TD side of me is unhappy about this change, but mostly I am wondering why.


Wish they’d just put a manually operated switch inside the coin door :frowning:


Now lets see, how did it start.

a) Williams introduced the interlock to protect the game configuration from being modified, accidential or provoked, with the coin door closed. Who knows if this was anything else than a silver bullet for the sales department.

Later to kill playfield high power too.

b) For repair-guy safety?

c) To protect against legal issues or complaints regarding safety?

d) Sales silver bullet against the competition?

e) To guard against accidential damage from shorting high power bus to sensitive electronics systems?

a) is hardly the reason now a days.

d) could be the reason, if the competition is bs’ing the importance of the interlock.

e) was never true. I have cook my fair share of ULN2803’s with the coin door wide open (due charged capasitor).

I am saying, with the big fine resolution screen and modernised control system and user interface, surely, it is possible to come up with something better that the interlock switch. Safe, intuitive and informative.

Coin door ball saver was also added by stern at I think at High Roller Casino rom 3.00

Probably safety. I’ve sen quite a few “techs” that work at arcades getting popped by coils trying to get balls unstuck from games. I use the word “techs” loosely but they are the people taking the glass off a game to get the ball.

They are easy enough to rig for tournament use. For the arcade, minimum wage techs and for home use, I’m glad to see them back.

As a TD, as long as I have Coin Door Ball Saver, I don’t really care if the flippers can be engaged or not. Balls will get plunged back out. Big deal. :slightly_smiling_face:


Do you only use modern Sterns for your tournaments?

No. Why?

WPC games don’t have a Coin Door Ball Save option. I guess you’re saying you’re happy with just the Sterns because they have this option?

I’m saying I don’t care if Sterns have an interlock or not because Coin Door Ball Saver is the catch all that works regardless.

I don’t particularly enjoy trying to place balls on flippers without messing anything up, so if that option is gone by default, I’m not going to be sad about it

I guess I’m also wondering why this would be a negative…other than you might now have to modify the game so that it has consistency with the other games that you’ve modified?

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This has given me the hilarious idea that I don’t even have to make some trap up during a stuck ball. Why make them risk draining when you could just open the coin door mid-flip?

The interlock is a UL requirement. Williams and DE/Sega/Stern protected both the 50V and 20V lines with it (actual voltages usually a fair amount higher, like 70 and 24). I’m not sure the history of protecting against the lower power coils as well (perhaps the original UL requirement is lower), but at some point in time, the minimum voltage you had to protect against was 50v. Since JJP’s system had 2 different 70v feeds to the IO board, both interlock leads were used for those instead of both high and low.

When spike came out, Stern switched to a 48v supply, so technically they weren’t subject to the requirement anymore. That’s why it could go away.


I put a used flipper rubber over the interlock switches on WPC games for tournaments. Works great.


To me the coin door ball saver and tilt disable are great to have, especially in tournaments. If you can leave the flippers enabled, then it is a win win.

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