Fix-It hints for your Twilight Zone Pinball

Well, I've been thinking on this for a long time ... TZ owners, here's your "fix-it" bible ...

Twilight Zone is one of the most complicated pinballs Williams/Bally has ever produced ... it's the only game that I know of that (in its prototype form) used all 28 coil drivers, the entire lamp matrix (64 lamps), the entire switch matrix (64 switches), all eight switches on an auxillary "9th" switch column (making it 72 total), and an entire 8-driver auxillarly coil driver board (used for 7 coil drivers and the 9th switch matrix column) ... plus all four flipper positions on the flipper board !

Added Together :

By the way, you are visitor number since Janurary 8th, 1996 !

First a disclaimer -- I will not take responsibility for ANY damage done to your machine by anything I describe. What I describe are things I have found work for me. I am an experienced pinball technician. They may or may not work for you, depending on your experience level. If you do not feel comfortable doing any fix or repair needed for your game, DON'T DO IT !

It's usually cheaper to hire someone to do it right than to hire someone to undo what you've done wrong and then do it right.

So now that you're scared to death to lift that screwdriver ... :-)

The Clock

TZ's clock is a wonderfully designed piece of mechanical engineering that can actually tell real time, if that option is enabled in the software.

Unfortunately, it has an achilles heel that can bring the whole mechanism to a screeching halt -- heat !

See, the Clock was originally designed so the lamps were on the game's lamp matrix ... for what reason I'm not sure, but probably to do some neato strobing effects ... anyways, the designers ran out of available lamp slots on the lamp matrix and the clock lamps were moved to the GI circuits (same circuit as the "Twilight Zone" in the backbox, BTW) ...

When this was done, the diodes needed for the lamp matrix were replaced with jumpers as they aren't needed for GI lamps.

Unfortunately, the result is light bulbs that get VERY hot from the GI circuit as they're on all the time ... and this heat will almost certainly destroy the optos in the upper parts of the clock as there is no ventilation for the heat to escape through ! What's more, the pins that connect the minutes opto board to the hours opto board get cooked by this heat as well and delaminate, causing a very poor connection between the two boards and spurious problems with the hours optos ...

The solution to this problem is to first replace the jumpers installed in place of the lamp matrix diodes (D1-D4 on the minutes opto board) with those diodes again. 1N4001 or 1N4004 diodes work fine. Direction doesn't matter as GI power is AC, but the PCB is actually silkscreened for the original diodes.

An additional nugget of info from Marc Howard is that you can install D2 and D3 in the reverse of the silkscreening ... this will cause lamps one and four to light on one half of the AC cycle and lamps 2 and 3 to light on the opposite half of the AC cycle !

Second, you need to remove the clock guts from the clock casing and drill ventilation holes in the clock casing. I usually put two in the back part of the roof for the back part of the clock (so the hours optos can stay cool) and two in the front part of the roof right over the light bulbs (between the PCB and the clock face) so the light bulbs' heat can escape. I also drill inlet vents on the lower parts of the sides in each section so cool air can come in. Natural convection will take over to cool the clock as the hot air rises, escapes, and cool air is drawn in to replace it.

You will also need to replace the pins between the PCB's if they are visibly cooked (they'll look tarnished) and any optos that have been damaged by the heat.

When you reassemble the clock, pay close attention to the instructions in the manual -- it has very specific steps to follow for proper clock alignment.

The Gumball Machine

The Gumball Machine is, if possible, a cooler piece of engineering than the clock. It's main point of failure is dirt. There is only one switch inside, called "Geneva" that is used to detect one revolution of the mechanism. If this switch gets too dirty, it can fail to make contact when closed causing a failure. Other points of failure are on the opto pair at the entrance to the Gumball (on the wire rail) ... Kevin and Keith once reported theirs broke off the wire rail ... anyways, these are subject to quite a bit of vibration and this can cause broken LED legs and failure. Lastly, the gumball popper, like all ball poppers, is subject to dirt that can occlude the opto's lens ... this will cause the game to think a ball is permanently in the popper ...

The Bridge Diverter

This is the thingy on the Right Ramp that 1) drops the ball into the left spiral for you to bang into the Piano or 2) hurredly gets out of the way on a Powerfield shot ...

It is connected via a pull wire directly to its coil, so if it doesn't go down, it's usually due to a broken wire, a bad coil, or something hanging the mechanism up ... assuming, of course, that the opto on the right ramp is functional ...

What is more common, however, are two problems :

Lastly, the hinge pin (part # 02-4837) can get very worn over time, causing a MAJOR wobble in the diverter carriage. This can cause both problems listed above.

The Powerfield

Most of the powerfield problems are electrical in nature, especially with the magnets. The biggest thing to watch out for here is that two plugs on the wiring harness are IDENTICAL. One goes to the optos, the other to the magnets and flashlamps. Needless to say, plugging them up backwards will put a 50vdc potential to your opto detectors and fry them but good.

Double check carefully before plugging this sucker back in ...

The Flippers

TZ's flippers are as follows :

I strongly suggest an outright replacement of : coil stops, coil sleeves, crank/link assemblies, and the coil itself if the sleeve won't slide in and out easily. The parts are inexpensive and replacing 'em is much easier than trying to resurrect worn parts. Worn parts have fairly obvious flat spots and/or mushrooming on the ends. You will also want to replace the return spring if needed ...

Parts needed :

One other thing to watch out for the the EOS paw on the crank -- this is the little arm that strikes the EOS switch blade. Normally there's a piece of 1/4" heat shrink tubing here to prevent metal from rubbing on metal, but on older flippers it has often rubbed off -- and the steel of the crank will cut right through the copper of the EOS switch. So if you find your old crank has worn through the heat shrink tubing, consider replacing the EOS switch as well -- part # SW-1A-194.

I align flippers so the facing of the rubber is perfectly parallel with the wall that feeds the flipper ... either the wall of the upper loops or the wall of the return lanes. This may or may not work for you.

Oddly enough, TZ shipped with red rubber ... the part # in the manual is for red rubber, but the name given in the manual is for yellow rubber

Under-the-Playfield Mechanicals

Be on the lookout for three problems (other than the Piano & Camera scoops coming loose) :


That's all I can think of for now ... I'm sure I'm gonna get plenty of corrections (I typed all this in off the top of my head) ...

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