Pinball Rehab

pinball repair and restoration

EOS (End of Stroke) Switch EOS (End of Stroke) Switch Hot

Most modern pinballs, up until about 1991, use an end of stroke, or EOS, switch on the flipper solenoid.  The purpose of this switch is to reduce the current to a flipper when it is held in the up position.  Like when you're cradling a ball in the flipper.

If high current was maintained for a long period, either the fuse would blow or the driver transistor or coil would burn out.  Most EOS switches are normally open and then close when the flipper is in the up position.  Some, like the Sega shown below, are normally closed and then open when the flipper is in the up position.

The red post in the photo depresses the switch thereby opening it.

With a couple of exceptions, EOS switches have been eliminated on newer machines.  In the case of Williams this is true since the introduction of the Fliptronics flipper control board and since around 1991 on Data East, Sega and Stern when they introduced the Solid State Flipper (similar to the Fliptronics).

Although some manufacturers later returned to using EOS switches in conjunction with a flipper control board (like the Baywatch in the photo).  The reason for this was due to poppers or VUK's, that could return the ball to the flipper at a high velocity.  If the flipper was in the up position the lower current would allow the flipper to be pushed down and the ball would drain.

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EOS (End of Stroke) Switch

The EOS switch would prevent this since when the flipper was forced down the switch would open (or close depending on the manufacturer).  The coil would again be provided with high current and the flipper could not be pushed further down by the ball where it would drain.