Twilight Zone Slot Machine Switch Modification
    by, 03/25/03.
    Copyright 2001-2003 all rights reserved.

    The 1993 Bally Twilight Zone slot machine playfield switch gets bent from collision with the pinball. This allows the metal slot machine ball scoop to be hit by the ball, splitting and breaking. If the scoop breaks, this can only be fixed by welding. Also, as the switch bends back, this can cause "air balls" when the pinball hits the switch (the bent switch acts like a ski jump). This causes broken playfield plastics (which are no longer available from Williams). Reinforcing the slot machine switch so it does not bend, prevents these problems.

The problem slot machine switch and slot machine scoop on the
Twilight Zone playfield. In this picture the slot machine switch
has bent back, allowing the ball to hit the side of the slot
machine scoop. This in turn has broken the weld, releasing the
top metal part of the scoop. To fix this, the scoop will need
to be re-welded. The bent switch will also need to be fixed, or
the problem will happen again. The plastic above the switch has
also broken, because the bent switch acts like a ski jump,
launching the ball into the air and breaking the above plastic.

Some of these ideas were originally conceived by Jonathan Deitch. He has a nice Twilight Zone "fix it" web page at I have been collecting many other people's ideas on this modification too. So most of this stuff is not "my idea". This is an accumulation of lots of TZ Slot Machine switch modifications I have seen.

NOTE: This document is largely obsolete because Pinball Resource has now introduced a special Twilight Zone target, part number A-18530-6E (the "E" is for "enhanced"). This new target has a wider, stronger mounting plate which prevents bending. Also the target backing plate is right angled (much like Capcom targets), which also prevents bending.

Pinball Resource's new TZ target,
part number A-18530-6E.

    1. If Welding is Needed
      It is very common for the side of the slot machine scoop to be split, and the metal tabs break. The only way to fix this is by welding. A TIG welder (Argon gas) will be needed. TIG welding will look the best and discolor the stainless steel the least. Do not have some "hack" arc weld this!

      There are some (welding) modifications that can be added to the slot machine scoop, if it already needs to be welded.

      First, a two inch fender washer can be added (welded or even JB Welded) to the side of the scoop to help strengthen it. The front of the washer can protrude in front of the scoop metal about 3/8", and be bent to the left (as installed, and playing the game). The bent edge is slightly trimmed off too. With the scoop installed in the game and a brand new Williams target installed, bend, cut, and fit the washer to its place. Then mark the washer's position with a "sharpie" and remove the scoop for welding. This will help prevent the scoop from breaking again, as the bent washer will be gently deflect the ball to the side.

    Right: A removed and broken slot machine scoop, with a bent fender washer
    in place, and ready to be welded, or even "JB Welded".
    Left: Washer installed in the game. (pictures stolen from James Swenson).


      Welding Slot Target Modification.
      A metal bracket can be welded perpendicular to the side of the slot machine scoop, preventing the switch from bending back ever again. To do this, first bend the slot machine switch target back to its original position. Then draw a line on the side of the scoop even with the back of the slot machine switch target. Take the scoop out, and construct a right angle metal (stainless steel) bracket. Hire someone that does TIG welding, and have the bracket welded in place on the slot machine scoop (and weld the scoop back together where the original Williams tabs broke).

    A piece of metal is welded to the side of the metal slot machine
    scoop to prevent the slot machine switch from bending back.
    (picture stolen from "Rebel").

      I personally don't recommend either of these welding modifications unless the scoop is already broken, and needs to be fixed. If that case, either or both of these modification are a good idea. If these modifications are made (especially the added metal bracket on the side of the scoop), the rest of this document is not necessary.

    2. If Welding is NOT Needed.
      This modification is a "bolt in" approach (no welding required), and is broken into three steps. Not all the steps are required; do one, two, or all of the steps. Also the steps work independant of each other. That is, step three could be done, but not steps one or two. The following parts will be needed:

      • Improved TZ target, available only from Pinball Resource, part# A18530-6E ("E" for enhanced) standup target (for step 0), $8.22.
      • Capcom standup target (for step 1).
      • Williams slingshot hinge bracket, part number A-17810 (for step 2).
      • 1/4" shrink wrap tubing (for step 2).
      • Coin box metal lid (comes with the game), or some thick gauge sheet metal (for step 3).
      • OR 4" of 1/8" stainless steel wire rod (instead of the coin box lid, for step 3).

      The ideal target is the new Pinball Resource target, part A18530-6E. The Capcom standup target is available from Prestige Industries 248-542-5530 ( or Mantis Amusement This target is used instead of the Williams target because it has an "L" shaped steel reinforced back, and is less likely to bend. Sega standup targets also use this "L" shaped reinforced back, but the switch target itself is a different style (and therefore is not recommend).

      I have not personally tried this, but the Sega target metal back may also be used in this manner. If a Sega target is the only target available, perhaps the "L" shaped back can be unbolted and then attached to the original Williams target.

      The Williams slingshot hinge bracket can be a used part. A very common part found on all Williams pinball games from the 1980s to present.

      The 1/4" heat shrink tubing is good to have around. I used this size tubing for repairing Williams flipper pawl assemblies. This tubing is needed for the part of the flipper pawl that contacts the flipper EOS switch.

      The coin box metal lid should have come with the game. It is a metal top to the coin box, with slots cut for coins to fall through. If using this lid is not desired, 1/8" stainless steel wire rod can be purchased at a local welding shop.

      Do All The Steps Need to be Done?
      Maybe, maybe not! I would personally recommend all of them, but they can be applied one at a time and then tested. If the target no longer bends, then stop. But from my experience, it is a good idea to do all the steps. For example, if only the new reinforced standup target is installed, the switch will still bend at the right angeled mounting bracket. If only the slingshot hinge bracket is installed, the switch's back metal brace will bend.

      This is assuming the slot machine scoop was not welded, and did not have a welded brace installed, as describe above (if these welding mods were done, the rest of these modifications are probably not needed).

    2a. Installing the New Switch

      Williams stand-up targets use a flat metal back. When hit hard with a pinball, the back will bend. When Capcom made pinball games a few years ago, they improved on this design. Instead of using a flat target back, they used an "L" shaped back. This prevented the switch back from bending. The only problem with the Capcom switches is they are "two lug" switches (opposed to Williams switches which are "three lug" switches). Pinball Resource took this one step further, and not only used an "L" shape back support, but also increased the size of the mounting plate.

      The two lug Capcom switches can be used, but the diode must be installed correctly. This unlike the three lugged Williams switches, where one lug is a "place holder" only for the switch diode. Capcom switches are very plentiful. When they stopped making pinball games, their excess inventory was dumped on the parts market. Many retailers bought these parts cheaply.

      Installing a Diode on the Capcom Switch.
      Attach the BANDED side of a 1N4004 diode to either lug of the two lug Capcom switch. The other end of the diode will attach to the switch wire.

Left: This switch is the two lug Capcom switch.
Middle: This switch is the three lug Williams switch.
Right: Pinball Resource's new TZ target.

      Modifying the Capcom Switch Back.
      If either of the two following steps are done, the Capcom "L" switch back needs to be modified. The modification involves "reversing" the back plate (the other two steps require this modification). Here are the steps:

      • Remove the "L" shaped back from the Capcom switch by unscrewing the two 1/4" nuts.
      • Gently tear the black backing foam off the bracket.
      • Use a 9/64" drill bit and drill two new holes on the opposite end of the "L" back brace. Drill the new holes with the same spacing and location as the original holes (but on the opposite end of the "L" shaped metal back).
      • Reattach the "L" shaped back using the new mounting holes, as shown in the picture below (the "L" part of the bracket facing AWAY from the switch). Essentially the switch will look just as it did before, but with the "L" protrusion on the left, not the right, as looking at the back of the switch.
      • Use Superglue and re-glue the black foam in the correct position on the "L" bracket (behind the target to cushion the blow from the pinball).

    Left: A original Capcom target.
    Right: A modified Capcom target with the
    "L" shaped back drilled and reversed.

      Installing the Capcom Switch.
      From the bottom of the playfield, remove the slot machine standup target switch. This is held in place with two 1/4" hex screws. In order to remove this switch, the playfield lamp circuit board next to the switch must be removed first. Fit the new switch into place with the same screws. The mounting holes are in the same position as the original Williams switch, so the Capcom switch will fit exactly the same.

    Where the slot machine target switch lives under the playfield.

      Attaching the Switch Wires.
      • Solder the WHITE switch wire to the DIODE non-banded lead, attached to the Capcom switch.
      • Solder the GREEN switch wire to the unused Capcom switch lug.

    2b. Installing the Sling Shot Hinge Bracket

      If the slingshot hinge bracket is not ordered separately (Williams part number A-17810), a standard Williams slingshot assembly can be taken from a "parts" game.

    A standard Williams slingshot assembly.

      If the entire slingshot assembly has been aquired, several parts can be discarded. These parts are the "L" shaped kicker arm and it's attaching spring clip. The only part needed is the hinge bracket.

      Once the hinge bracket is isolated, the pin which holds the "L" shaped kicker arm needs to be removed. Using a bench grinder, grind off the end of the pin. This will allow the pin to be easily knocked off the bracket with a hammer.

    The discard slingshot assembly parts, and where to grind
    the hinge pin.

      After the hinge pin is removed, use some 1/4" shrink wrap tubing and surround the two protursion points of the bracket.

    The modified bracket with skrink wrap tubing installed.

      Installing the Sling Shot Hinge Bracket.
      Install the sling shot bracket behind the switch, as pictured below. It should just fit into place snugly. Because we reversed the "L" shaped switch back, the sling shot hinge bracket should have no mounting problems.

    The sling shot bracket is installed behind the new Capcom switch.

    2c. Installing a Reinforcement Brace.

      Shown below are two different methods to reinforce the back of the slot machine target. Both are pretty easy, just pick the method that makes the most sense for you.

      Target Reinforcement Brace, using a Coinbox Lid.

        Obtaining Some Metal.
        Some heavy gauge sheet metal will be needed for this modification. The heavier the better (but don't go too crazy, as it does need to be cut!).

        The one part on every 1990s game I find NO use for is the coin box lid. I'm sure it has great usefulness for operators, but for me, it's just something I set aside and never use. I do use the coinbox to throw parts in, but the lid just gets in the way.

        So here's my metal! Not as thick as I would like to use, but hey, it's there! The rolled metal edges work perfect too for this application (yes, it does matter which corner of the coin door is used; see the picture below).

      Marking the coinbox lid for cutting. Make sure to use the corner
      shown, to keep the rolled edges in place for our application.

        The Dimensions.
        The piece of metal that needs to be cut should be 2 1/8" high by 2 5/8" wide. Then use the picture below to cut the metal to proper shape. It is not a rectangle, as there needs to be a 1/2" high by 1 1/8" wide "tab" coming off the rectangle.

      The dimensions of the metal. The blue circles are where the two 5/32"
      holes are drilled.

        After the metal is cut (I used a band saw with a metal blade), drill two 5/32" holes in the "tab". Drill them as close to the bottom edge of the metal as possible.

        Bend the Metal Tab.
        Next the metal "tab" needs to be bent 90 degrees. To do this, put the metal in a vice, with the tab in the jaws of the vice. Then beat the metal rectangle over 90 degrees with a hammer (this works amazingly well). And YES, it does matter which way the tab is bent (it needs to be bent towards the rolled edge side of the metal). Reference the picture below for help.

        After the tab is bent, put a piece of electrical tape on the adjacent rolled side.

      The metal after the tab is drilled and bent, and the added electrical tape.

        Installing the Brace.
        Lift the playfield and remove the adjacent lamp board, and the two ROUND targets (which are around the corner from the slot machine target) from the bottom of the playfield. Also remove the slingslot hinge bracket, installed earlier in this document.

        Now the metal brace can be installed in the game. Position the brace so the front edge (with the electrical tape) is pressed against the back of the slot machine target. The back edge of the new brace should be against the slot cutout in the playfield. There should be very little play.

        The brace may need to be angled very slightly to get the front edge of the brace to touch the back of the slot machine target (but do not angle it too much). Note how the new brace fits on the "inside" of the "L" shaped slot machine switch back (that is one reason we reversed the switch back).

        Screw the brace to the playfield with two 1/4" head hex wood screws (same style of screws used to hold the targets in place).

      The new brace installed from the bottom of
      the playfield, up against the slot machine
      switch back.

        After the new brace is in place, re-install the round targets and the lamp board.

      The top of the playfield with the new brace installed and the top plastic removed.

      The top of the playfield with the new brace and the plastic installed.

      Target Reinforcement Brace, using a Small Rod.

        Instead of sacrificing the coinbox lid, this version of the target reinforcment brace uses uses a 1/8" stainless wire rod about 4 inches long. The rod is formed to extend from an existing playfield screw to the top of the depression in the stock slot target switch backing plate. According to Ken S (who came up with this idea), this fix has held after a lot of use.

        A 1/8" stainless steel wire rod was bought from a local welding supply company. The rod is then heated red hot before bending (use a Mapp gas torch, but a propane torch should also work). After forming the "eye" (where the screw attaches, see the picture below), quenched it in water (basically heat treating the rod to resist bending). The eye has a slight up bend that can't be seen in the photo. Bends other than the eye were made cold.

        If using this reinforcement wire with a modified Capcom switch, be sure to put a 8-32 bolt through the top placement holes in the switch backing. Otherwise the wire may try and go into the lower hole, rendering the reinforcement wire useless.

      The stainless steel wire rod after forming. The grids in the
      background are 1/4", showing the rod (after forming) is
      about 3" long.

        Although Ken has not had any problems with the screw loosening, it might be a good idea to use a #6 x 5/8" or 3/4" rather than the #6 x 1/2" original screw, because of the additional thickness of the wire rod.

      The wire rod installed. The metal ball guide screw is used to secure the wire rod.

End of Twilight Zone Slot Machine Switch modification.

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