On the bottom board, to the right of the score motor, is the spin unit. This is a stepper with a small rectangular metal spinner and a bakelite finger attached to the stepper gear shaft. The finger is positioned such that it can flick the spinner and make it spin.
The spin unit steps up several times to wind up its torsion return spring. When the spin function is activated, the reset coil of the spin unit stepper is energized, releasing the gear and allowing the torsion spring to snap the finger back to the reset position. As the finger snaps back, it flicks the spinner and makes it spin. A switch attached to the metal spinner pulses the spin pulse relay.
The spin pulse relay pulses the spin relay and also sends current to a small time-delay module consisting of a diode and a capacitor. This delay module is used to hold in the spin delay relay while the spin pulses occur. Each pulse from the spinner, in addition to stepping the spin relay, re-charges the capacitor, which keeps the delay relay pulled in. As long as the pulses occur fast enough, the capacitor stays charged and the delay relay stays in. When the pace of pulses from the spinner slows down enough, the capacitor discharges and the delay relay drops out. This causes the selected card to be spotted and also terminates the spin function.
Here is a picture from IPDB showing both the spin unit to the right of the score motor, and the delay module located just behind the left side of the spin unit:
As for cleaning lamp sockets, the best thing to use for playfield sockets is a #443 wire brush attached to a Dremel tool running at medium speed. Push the brush directly against the center contact down inside the socket for a second or two, and then run the side of the brush around the inside of the socket in the area above the center contact for another second or two. Don't push the brush down into the socket between the side-wall and the center contact, as this will put undue stress on the central rivet holding the socket assembly together.
For lamp sockets in the head, you can use also use the #443 brush, but be aware that the center contact is a spring rather than a metal post.