I finished a top to bottom restore of my Slick Chick early this year. It seemed to work flawlessly except for one nagging intermittent issue that was annoying. Occasionally after a couple of games the pop bumpers would stick on intermittently, occasionally going off after I hit another bumper but usually forcing me to switch off the machine to reset the game.
I filed or cleaned over and over again all the relevant switch contacts on all associated relays and on the scoring relays and it seemed to improve things for a while, and this stopped the game freezing with a relay locked on. However, a bumper relay would still occasionally stick on momentarily going off only when I hit another bumper. I must have lifted the playfield 50 times since trying to find the root cause. No other game I have had this issue. I started to look for a magnetized coil plunger and studied the schematic trying to see a hidden connection between the bumpers and switches etc. I never found a suspect switch that explained what was causing this issue and never found a coil with a sticking plunger until yesterday! It wasn't residual magnetism but a mechanical fault.
The 0-9 stepper has a connected 3” bell to signal scoring 1 point. As you score points it hammers that bell as the coil plunger pulls in.
0-9 Stepper with bell
This I thought was a cool stepper that is held parallel to the mounting surface with 3 pins as it allowed you to mount it quickly. Because it is not perpendicular to the mounting area you cannot see the coil activating only hear it work because of the bell this is not so cool after all.
I unclipped the stepper and was watching the coil activate as I kept closing the N relay (yes, with the power on). The coil and plunger was chattering and seemed that this might be causing the issue…and it was. What was happening was the bell striker was too close to the bell so as the stepper coil pulled in the plunger, the coil plunger never reached the coil stop. The striker hit the bell first, not releasing the stop and deactivating the N relay EOS switch every time. There is also an adjustable stop and it was not adjusted correctly either. The fix is so simple, re-adjust the bell position away from the striker.
Adjusting the bell and coil
I have never seen this issue mentioned in any search before (I made many searches here, on RGP and google) as it is probably so simple to so many it doesn’t need documenting. Anyway if others make my mistake hopefully you find this explanation a lot quicker than I did.