Most chime assemblies include a resting pad or grommet for the chime plunger
to rest upon in down position. If this pad or grommet is missing the coil
may not have enough power to draw the plunger up and the coil will just hum
instead of ring. A small strip of self-adhesive weather-stripping works
well for replacing this pad or grommet. Just raising up the plunger a
quarter inch is enough to get the mechanism to function properly.
This problem is possible on electromechanical and solid state games with
chimes. This problem was first discovered on a 1977 Gottlieb Sinbad,
a solid state machine.