Discs of Tron

Ever since I played this game many years ago, I have been fascinated by it. It is truly an experience to play this game. The game cabinet is a marvel, and the originality of the game itself makes Discs of Tron one of those games that just stands out on its own.

The first Discs of Tron I owned was in decent condition, about a B. I was fortunate that the game, after pieced back together, worked perfectly fine. Unfortunately, I got to a point in my life where I had to move, and the Discs of Tron could not come with me :-(.

However, I knew some day I would have to get another one. To make a long story short, I eventually found another one that I could have for the entire sum of $0, as long as I could haul it away.

Unfortunately, this one wasn't in the greatest condition.

I worked hard to restore the game cosmetically. The bottom of it had some minor damage from being slid around with no feet, and the bottom panel under the back art actually fell off. Fortunately, all the artwork on the game was intact, but the artwork on the giant glass with the man on it (foreto known as the "man glass") had bubbled :-(.

However, owning one again presented the same problem as before: how does one store and move around such a monsterous game? The beast must weigh around 600lbs, and there is no easy way to transport it considering its odd shape (slanted rear near artwork prevents using a fridge dolly) and weight distribution.

So I cut it in half.

"WHAT!!??!?" you might be screaming? Let me reassure you, this was not a "grab a chainsaw and start cutting" procedure. Damned if I wanted a ruin a beautiful cabinet, but there was NO WAY to get it in the basement without doing it, and I promised myself never to own a game I couldn't move on my own.

The "Environmental" Discs of Tron (its official cabinet name) CAN NOT be taken apart "nicely". The bottom is a single board which spans the entire length of the game. As is the top. The only way to separate it would be to break the glue and staple bonds between the side walls, pretty much guaranteeing that you'd ruin the structure of the entire cabinet. Not to mention, even if you did want to do this, you've now got to move around either end of the cabinet with no back or top! How are you gonna do that with a moving dolly?

However, further analysis revealed this: each side wall is made of two pieces that join flush with each other, and that joint is not glued. This joint joins the back half of the cabinet (with the glass art, both "grid glass" and "man glass") to the front half. Operators in the past have sawed STRAIGHT DOWN this line, and converted the front half to be a stand-alone Discs of Tron upright. The back, with all its lovely art, was thrown out in the trash.

The Surgery

First things first; I completely stripped the game of all artwork and parts, including the floor piece (the disc art), leaving only the wiring harness in place. Under the disc art, you will find two sets of wires which lead to the rear piece of the cabinet. One set contains many thick wires; this is the wiring for the rear fluorescents. The other set contains about 4 thin wires which provide the audio to the rear speakers. I would need to make these connectorized so I could separate the front and rear pieces easily, so I gathered some slack, and cut the wires near where the joint would separate. I realized that the wires for the audio went another three feet before they connected to the board, so I could have just pulled the connector in hind sight. However, that would mean each time I disconnected the pieces I would have to thread that wire back underneath the front foot fluorescent lamp (not trivial), so I still think I did the right thing.

The nice thing about this surgery is this; once it's done, it's virtually unnoticable, and here's why: First of all, the bottom disc art is applied to a large sheet of metal. This metal actually spans the joint. So the bottom cut is completely masked. Second, the board that contains the front speakers and the lamp sequencer slants from the monitor glass of the front piece into the rear piece, thus spanning the upper joint. So the top cut is completely hidden, also. The sides where the split is made already has a seem where the two sides pieces join. So unless you can see the very top or the bottom of the cabinet (both of which are unlikely), there is NO WAY to tell it has been cut at all.

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Which is a Good Thing (tm).

On with the show! I turned the cabinet on its head, climbed a ladder, and drew a straight line from one of the side joints to the other across the bottom of the cabinet. I did not want to cut all the way across the bottom with the circular saw, as the circular saw takes out about 1/16" of wood as it cuts, and cutting straight across would take that out of the sides of the cabinet, too, thus ruining my flawless seems! So I had to drop the blade into the bottom of the cabinet a few inches from the sides. There was still about 1" or so of wood left on either end left to cut, and I would use a jig saw to cut the rest of the way to the sides. But I didn't want to make the separation just yet.

I lowered the cabinet carefully on its side on top of some cushions (I ain't gonna ruin the side art!). I then used the jigsaw to complete the cut across the bottom of the cabinet. Now I carefully put the cabinet upright again (top side up) and repeated the circular saw procedure, but made the remaining jigsaw cuts with the cabinet still upright.

Ok, now the bottom and top boards are completely cut and are no longer holding the two pieces together. At this point the cabinet should have fallen apart at the seams.

However, there was one more thing I hadn't anticipated: the front speaker board which spans the upper joint is attached to the sides of the rear piece via two wooden blocks about 2" long each. These are concealed BEHIND the front speaker board. There was no way of knowing these things were there before I started the procedure. These blocks are attached with some glue and staples. Standing in the cabinet and pressing up on the rear piece's ceiling, I was able to apply enough pressure that the glue and staples gave way and the rear piece came cleanly away without a problem as I had originally hoped. Using a chisel, I removed the blocking as they would hinder putting the cabinet together later on. Removing this blocking has no adverse effect.

Ok, so now I had it in two pieces. After adding a 12 pin connector to one set of wires, and a 6 pin connector to the other side, I had the wiring harness back intact. I moved the two pieces back together as they were originally, and screwed two large draw hasps across the top of the cabinet to hold the top together. The metal floor disc artwork then screws to both rear and front pieces, holding them together. Lastly, for additional support near the floor seam, I slid a board underneath the cabinet which spans the bottom joint.

And the cabinet was back together again, and I couldn't tell it had ever been apart.

Lamp Sequencer Board

Discs of Tron has a nice little light show near the front speakers whenever you kill Sark. This light show consists of 5 lights on either side sequencing forward or reverse.

The lights are 194's, which run off +12VDC unregulated. One side of the lamps is always connected to +12VDC unregulated. The lamp sequencer works like this: there are 5 MPS2222As (one for each lamp) which, when turned on via the sequencing lamp circuit, connect the other side of the lamp to RET (ground), thus completing the circuit, and lighting the lamp.

To debug the lamp sequencer, first start with the lamps itself before you go mucking with the lamp board. There are two boards mounted on the front speaker board which contain 5 lamps a piece. One side of the lamp sockets are all connected to a +12VDC rail. The other side of the lamp socket has a separate wire going to the harness. When this side is grounded (or connected to a lamp RET), the lamp lights. Here's how to test individual lamps/lamp sockets: With the lamps inserted, test each lamp with a test lead by hooking one end of the test lead to the separate wire side of the lamp socket, and the other end of the test lead down to the grey/red wire which is connected to the lamp sockets inside the coin door. If the lamp lights, obviously the lamp is ok, so there is either a bad connection, or a bad lamp driver board. It is easy enough to test continuity of the wiring harness from the the lamp socket to the lamp sequencer board.

Next, trace the wire from the lamp that is not lighting back to the lamp sequencer board. From the traces on the board, you can determine which MPS2222A controls it. Connect a voltmeter and read the voltage at the resistor which is connected to the MPS2222A in question. Run the lamp sequencer test (any of the four will do). If the needle jumps (assuming analog voltmeter), then the MPS2222A is being pulsed on, but is not working. If there is no pulse, there is something wrong with the lamp sequencer logic, or the boardset signals that tell the board which way to sequence needs to be verified.

One last way to check the lamps and MPS2222A is to take a test lead and connect the outside legs of the MPS2222A in question, and turn the game on. If the lamp lights (and that MPS2222A did get a pulse in the test above), replace the MPS2222A. MPS2222A is a cheap transistor available from Mouser for a few cents a piece.

Fluorescent Lamp Relay Boards

There are two fluorescent lamp relay boards; they are the same, so don't worry about getting the two mixed up. The upper one controls the rapid flashing blacklights at the CP, the front feet, and rear feet. The lower one controls the on-off of the two background lights: one cool white which lights the art from the back, and one blacklight above the monitor which lights up the backglasses. The blacklight above the monitor can be reached by removing the front speakers.

All of these "rapid start" lamps have a dual 6VAC transformer attached to the fixture instead of the typical FS-2 starter. The theory is this: 6VAC is constantly applied to the fluorescent tube to keep it "hot". When the relay is activated, it allows the other 6VAC to flow through, making 12VAC applied to the lamp, thus lighting it.

During the game, the lower Relay Control Board will turn on the background lights (the blacklight above the front speakers, and the cool white behind the backdrop art) whenever the 3D game grid is displayed. Upon bootup of the game, these fluorescents will be off, but turn on in demo mode when the game grid is displayed. The upper Relay Control Board is used to strobe the control panel black light, and the two blacklights by the feet. These fluorescents are normally on, but strobe when your player is killed.

If you fluorescent lights are having trouble coming on, there are a few things you can try. First, I would recommend replacing the relays on the Relay Control Board. This silver box is the most likely culprit. You can purchase the same relay in a plastic case for about $12 from XXX, part number YYY. If that doesn't fix it, connectors may be the problem, or one of the balast transformers (I had one that was burned out on mine), or try replacing the bulbs.

Squawk & Talk board

Squawk & Talk is a popular sound/speech board used my Bally Midway in the early '80's, mostly in their pins. There is already an excellent document written by a pinball enthusiast which discusses the Squalk & Talk board in great detail. Refer to the document here. NOTE: The pinball Squawk & Talk board is a different "version" than the one used in Discs of Tron. Discs of Tron is an "MCR II" version of the Squawk & Talk. The main differences are capacitor values, use of an external volume control, and no AY-3-8912 chip on the EDOT Squawk & Talk board. Keep this in mind when reading this document. Do not follow it blindly!

DOT uses only 3 of the EPROMs on the S&T board. U2 and U6 should be unpopulated.

These are the phrases from the game which can be accessed in the test menu of the game:

Optical Encoder

A common problem with this game is that the optical encoder wheel does not behave properly. If the wheel has trouble moving in the right direction, adjust the optical wheel's distance from the opto. If the "marker" is moving too far too fast ("jumping"), check your connections, mostly the Mate'n'Lok connector between the CP and the game harness. The output is digital, and if the marker is jumping, a bit is being dropped.

The game uses the Optical Encoder Deluxe II. There are several different versions of the Optical Encoder (see the MCR FAQ), but the schematics for them are very similar, so the schematics for just about any version should be helpful.

BTW, the board also has CLK and DIR output running along the board, so you could pull them off the board and use the opto controller for games which use just CLK and DIR (Atari Blasteroids and Temepst come to mind).


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