Be sure that the EOS switches are opening for each flipper when the flippers are in the up position. If any EOS switch is not opening, that will cause a loud buzz from that flipper, and the coil will fry if it is kept energized for any length of time.
If you increased the flipper return spring tension, that will cause a louder hum. If that is the issue, you can reduce the hum by going back to the original spring tension. If that makes the flippers too powerful, you can adjust the EOS switches to open sooner during the flipper stroke to reduce the flipper power.
If the coils are loose in the brackets, that will cause a loud hum. To fix this, loosen the back bracket screws, and push the back bracket tight against the coil bobbin while you re-tighten the screws. The best place to push a coil bracket forward is along the bottom edge of the screw tab (the short lip with the screw holes in it) while the screws are in the base plate, but still loose. Pressing the bracket there should make the bracket look a bit like it's leaning back, with some space along the top edge of the coil bobbin. Hold the bracket in this position while you tighten the screws. The bracket will straighten up and the coil should be clamped in good and tight.
If a flipper is still buzzing, loosen the coil stop nut (with the flipper still fully assembled) and then re-tighten it. Each time you do this, you will rotate the coil stop a bit inside the coil sleeve. There may be a position where the face of the stop and the end of plunger meet that is less noisy.
If I still have a noisy flipper after doing all of the above, I'll dis-assemble the flipper and dress the face of the coil stop (or replace the stop if it looks bad) and I'll also dress the plunger end. Then I'll re-assemble the flipper and do the coil stop rotation exercise until the flipper quiets down. Sometimes I need to repeat this process a couple of times. It can be rather tedious, but it almost always seems to work for me.
- TimMe
Chesterfield, MO
