Quoted from shirkle:
I’m planning to pick up a JP in about a month. I’ll have only a few minutes to look it over and test it before buying it. What should I quickly check for before purchase?
If you don't have much time, this video shows quickly most of classic problems with the JP.. other things to check, burned electronics in the front panel and under the playfield (mostly the power supply is likely to have problems), rubbers, broken plastic playfield, and mostly, the decoration, check that everything is here because peaces are hard to find. The mosquito amber, the 2 pteranodons... (you can help yourself with good quality pictures from internet so you wont forget anything) also there are colored rubber cover for some bulbs most of the time missing (Top of the ramp Door, control room ect...) mylar or no mylar, but a lot of mylar is scary as hell. To finish, do a dianostic mode checking the switch/lights/T-Rex.. And the shaker, make sure it is working. A new shaker is 150 euros
All of this, estimated right can help you to get down the price. Trex not working could be a 200 euros motor broken, or decoration missing can get expensive, 50 euros for the two pteranodons that were missing on mine. Amber mosquito almost impossible to find! and very pricy.
Now you have to find someone next to you who owns a JP and exerce yourself to do all of this in a few minutes
Here a link of the video, good luck with your JP