From: iott@rtsg.mot.com (Joel K. Iott)
Subject: Solid-State Flippers (was: Re: Williams flippers)
Organization: Motorola Inc.
Date: Wed, 26 Aug 1992 15:28:25 GMT

In article <SBB.92Aug24222041@panix.com> sbb@panix.com (Steve Baumgarten) writes:
>
>Has anyone found this (weak Williams flippers) to be a problem lately?
>I think they've licked it with their new solid state flippers.  They
>may suffer from other problems, but in general, they seem much more
>reliable overall than the "classic" flippers.
>
>I think they did them just right: good feel, good strong flips.  I
>certainly wouldn't want to go back to the flippers on DR. DUDE and
>PARTY ZONE which seemed constantly to need a tune-up in order to get
>the ball up those steep ramps.  In contrast, I've never had a problem
>getting the ball up the Bear Kicks ramp in TAF -- at least from the
>left flipper.
>

I believe "solid-state" flippers can still become weak over time since what
wears out is the flipper coil(s).

I've seen this myself on a Terminator 2 game - it become very dull to play as
the shots were weak.  Then the repair guy replaced the flipper coils, and it's
fun to play again.  I am assuming that T2 has solid-state flippers, as it is
a recent game.

The following is what I believe to be true about "solid-state" flippers.  It
really should be added to the FAQ.  Note: I am NOT saying that Steve asked a
FAQ.

Sources:
various explanations on r.g.p I've seen
my ownership of pre-solid state machines
speculation (i.e. guessing)

Comments, anyone?


What is a "solid-state" flipper?

[A note should be added here about EM games with AC powered flippers, as I
don't know how they work]

DC powered flippers have two different coils that power the flipper stroke. 
The first coil is used for the "power stroke", which moves the flipper from the
rest position to the raised position.  A switch, called the end-of-stroke, or
EOS, detects when the flipper has reached the limit of its movement.  The EOS
switch cuts the power to the first coil and energizes the second coil, which is
used to hold the flipper in the raised position. 

The second coil is weaker than the first, as much less energy is required to
hold a ball on a flipper, than is required to reverse the direction of a ball
with downward velocity.  The two coil/EOS arrangement helps retard the
degradation of the flipper coils which occurs over time.  Coil degradation
happens faster with higher currents and prolonged energization of the coil.

On pre-"solid-state" machines, the EOS directly switched the voltages to the
flipper coils.  This voltage is typically ~40VDC.  The high voltage caused
arcing of the EOS contacts and eventually wore out the EOS switch.  Machines
with broken EOS switches never turn off the power-stroke coil, which will
quickly burn out the power-stroke coil. 

[Is there another symptom of this, like the flipper going to the raised
position and then "vibrating" ??? ]

"Solid-state" flippers attempt to solve this problem.  Different manufacturers
have adopted different solutions.  Williams has changed the arrangement such
that a normal 5V voltage (like other playfield switches) goes through the EOS
switch.  A EOS switch closure is detected by the computer controller, and the
computer shuts off the power-stroke coil and turns on the hold coil.  Data East
has eliminated the EOS switch altogether.  DE turns off the power coil after a
set amount of time and turns on the hold coil.  The flipper control is
"solid-state" in the sense that the computer plays a part in activating and
deactivating the coils - but the EOS switch still exists on Williams machines. 

[ I am guessing about how Williams work - anybody know for sure?  Anybody know
about Gottlieb? ]

Players generally feel that Williams solid-state flippers work much like the
"classic" flipper arrangement, although opinions vary on this.  Players tend to
dislike the Data East flippers. 

The lack of the EOS switch may hinder the Data East machines, as the computer
has no feedback as to the actual postion of the flipper.  DE machines switch
coils at a pre-set timeout regardless of flipper position and ball contact. 


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