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Rawr! Several small issues on this Jurassic Park. First up: balls not ejecting properly from the trough. These double-coil troughs are a pain to service. One coil to release a ball to the up-kicker, and another coil to fire the ball into the shooter lane. This one was sometimes failing to release a ball to the  up-kicker, and was also not strong enough to get the ball from the up-kicker to the shooter lane. So, whole assembly was taken apart, cleaned, and serviced with new coil sleeves installed. A fair bit of rust in the trough, too, which was cleaned up. Once that was done the balls started moving through the trough and into the shooter lane properly. Some of the trough switches had wires or diodes hanging onto them by a thread, so these were resoldered while I was here. 


Next up was the game "going dead" at random i.e. flippers going dead in the middle of a game. The symptom was actually the game incorrectly sensing that the ball had drained into the trough, thereby cutting power to the flippers. Deactivating the flippers at the end of the ball is normal, but this happening at random during a game is not. The cause turned out to be a switch matrix issue. Several switches in the game would trigger others on a different matrix row. One of them was triggering the trough switches. After a fair bit of switch checking I found the issue at the right ramp exit switch. The column and row wires were crossed because the switch lugs and diode had been mangled and smushed together. Separated the lugs and the switch matrix was back to normal.  


An issue with the T-Rex. It wasn't picking up the ball all of the time. His jaw will only grab the ball when it senses that he is at his lowest position, which is sensed by a microswitch on the underside of the assembly. This "bottom" limit switch was out of adjustment, and wasn't getting triggered on some occasions, so the jaw was not closing. Adjusted the switch for better activation. Another tell-tale sign of this is T-Rex's mouth hitting the playfield. It should never go that low; it should stop short.


Last issue. Ball was sometimes not getting kicked out of the right VUK. Someone had done some work on this assembly before; there were zip ties all over it. But they weren't the problem. The cup of the VUK was sitting too high, blocking the ball from rolling onto it. The switch actuator was actually putting too much upwards pressure on it. Adjusted the switch so the cup sat level with the subway, so balls could roll easily onto it. Issue fixed!


T-Rex is back to terrorising Jurassic Park! Rawr!