Williams System 6 and 7 Pinball Machine Flippers - Coil Stop Upgrade

Certain early solid state Williams Pinball Machines came from the factory with non replaceable coil stops.  When these coil stops wear out the entire flipper base plate needs to be replaced. 

Affected games include: Firepower, Blackout, Scorpion, Algar, Alien Poker, Barracora, Black Knight, Cosmic Gunfight, Defender, Firepower II (some), Joust, Jungle Lord, Pharaoh, Solar Fire, Time Fantasy, Warlok.

This modification allows you to use the existing flipper base plates, retain original flipper geometry, and use replaceable coil stops.

Instead of the modification listed here another option is to replace the entire base and mechanisms with the newer WPC style flippers.   This is a good way to get replaceable coil stops - and all the WPC flipper parts are readily available from many sources. 
However, this does not keep the original flipper geometry and also requires changing the flipper bats to WPC style.

After this modification, the flippers can be serviced using WPC coils stops, links, and plungers.  But also retain the original coils, bats, and  geometry.  

Note: In addition to what is listed in this guide, I also enlarged the hole in the factory flipper pawls to accept a #10 bolt.  This allows you to use WPC style flipper plungers and links. 

After doing this to both flippers on Firepower the flippers now work great.  Making the lock at the top of the playfield via the left spinner is easy - plenty of flipper power.

Below is how to do the modification.

Here is a pic of the removed factory base plate.  Note the worn coil stop.  Next to the plate is the WPC style coils stop.

First Step is to bend the coils stop portion so it is flat relative to the rest of the plate.  I did this in a vice.  I also applied heat from a propane torch to help the metal bend without cracking.  Not sure if this is necessary but why not.  Go slow.

Here is the result.  Notice that the it is not completely flat and the mounting tab is a little out of alignment.

So here I straighten it out a bit.  You could also use a hammer and a flat surface to do the same.

Then cut off the excess metal.  Cut just below the original coil stop.

Now using a coil and WPC coil stop, mock up the assembly and mark where the holes need to be drilled and tapped.  Center punch the holes for the coil stop, take everything back off the plate, then drill and tap holes.
flip 6

Here I am tapping the holes to accept #10 32 bolts.

Now it is done and ready to put back in the game.