Jurassic Park "ball missing" problem

KingOfTron

Member
Joined
May 13, 2009
Messages
415
Reaction score
7
Location
Arizona
So lately my JP performs a ball search for a couple of minutes when the machine is turned on and the display indicates a ball is missing. All the balls are there, and after playing around with it, I discovered that one of the trough switches wasn't recognizing that a ball was sitting on it. I bought a replacement switch and switched it out last night, but I'm still getting the same message. Could it be the diode on the switch? Is there anything else it could be?
 
Last edited:
Could be a divot in the metal of the ball trough?

Switch needs to be adjusted?

Does the switch work if you push it all the way down by hand?

Wired correctly and the diode on in the proper orientation?
 
Could be a divot in the metal of the ball trough?

Switch needs to be adjusted?

Does the switch work if you push it all the way down by hand?

Wired correctly and the diode on in the proper orientation?

The switch screws in pretty firmly with 2 small screws, so it's definitely in the correct position. The switch still does not recognize a ball if you push it all the way down by hand. The wiring an orientation are all correct. Im not sure about a divot though, where in the metal would it be?
 
Sometimes there is a divot in the ball trough, so the ball doesn't sit in the right spot in the trough so the switch doesn't activate. But if the switch doesn't function even by hand, then that is irrelevant.

Try some of this?

If a Bad Switch is Found.
If a switch does not work, check these things:

Check the switch wiring "up stream". Switches are wired in a "daisy chain". If a switch row or column wire breaks "up stream", ALL the switches daisy chained after the wire break in that row or column will not work!

If it's a micro-switch, check the actuator arm. Make sure it's adjusted properly. Listen for the micro-switch's "click" when activating. No click usually means the switch is mis-adjusted or broken.

Check that the wires going to the switch are soldered well, and haven't fallen off.

Check the continuity (using the DMM's continuity setting) of the wire between this switch and another working switch in the same column (white wire) or row (green wire).

Check the switch to make sure it works. Use the DMM's continuity setting, and put one lead on the "common" lug (the lug to which the banded end of the diode connects) of the switch. Put the other lead on the green (normally open) switch lug. The meter should only beep when the switch is activated, and not beep when the switch is de-activated. Move the DMM's lead from the green to the white wire (normally closed) switch lug. The meter should beep when the switch is de-activiated, and NOT beep when activated.

Check the diode on the switch. Make sure the diode is connected properly, and is working
 
How can I tell if it's the diode?

Pinrepair.com and pinballninja.com detail how to do this. But if the new switch came with a diode on it, then I would look elsewhere like tomdotcom indicated. But it never hurts to check the diode. You test the diode with a multimeter set on diode test mode. The black lead goes to the banded side of the diode. You should get a reading between 400 and 600.

My JP is rather picky about the ball trough switches. They have to be adjusted and bent just right so the balls roll down the trough without getting stuck but still trigger the switch. However if your switch doesn't work in diagnostic mode, this obviously isn't the problem.

I always check the diode first. Then look for connection problems. Then go to the backbox.
 
Thanks for the tips, I'll check it out when I get home
this afternoon. Is this here the diode for the trough switches?

http://www.pinballlife.com/index.php?p=product&id=173&parent=101

Yes, that is the right diode to use. I believe a 1N4004 is actually a more robust diode than what was used from the factory. Most people just buy 4004 and use it for all switches and lamps since the cost difference is minimal and they can be used in more situations when fixing other things on a pin.

greatplainselectronics.com is a great place to get components.
 
Does your game have the manual inside or have you used the diagnostic tests on a pinball before? Don't guess if you have a issue with a switch, put the game in test and check it with the switch test built into the game. Remove the cover plate over the ball trough area and manually roll the balls, one at a time thru the switches and watch the display to see each switch being read by the computer. Thats the best and easiest way to start to diagnose your issue.
 
Last edited:
You may have a whole row of switches out possibly as well. Check the switch matrix, I believe the trough switches are all in one column. Find where your bad switch is on the table, then check the other switches in the row to make sure that you don't have a bunch of switches out. If you do, you'll need to do some board work.
 
Back
Top Bottom