Battlezone Cabaret – Retrace line issue SOLVED!

Battlezone test mode showing retrace lines.

Battlezone test mode showing retrace lines.

No sooner had I gotten my 1980 Atari Battlezone Cabaret home and working, when a small but potentially annoying video issue became apparent.

If you are unfamiliar with the differences between Raster and Vector monitors, here is a brief introduction:

On my game, there was something going on with the Z-axis video circuit, which was causing a line to remain visible between vectors. These are known as Retrace Lines. This was something that was completely tolerable at first, since I was going from NO Battlezone to an imperfect Battlezone, but I was also quite aware that this would be a serious annoyance before too long.  Most of the time this can be addressed by adjusting the brightness and contrast pots on the monitor’s deflection board.  In my case, adjusting wasn’t doing the trick, so something else was at work.

I was lucky enough to be able to run some tests on the PCB which excluded the monitor as the source of the problem, so I knew I was looking at a board issue. This is a great example of a time when the game’s schematics would be really handy.  Luckily, these are available widely on the web. If you can’t find them, look right here:


Close up of schematic sheet 2B, including IC P9.

With a little guidance from some KLOV members, I was able to use my logic probe to work my way back through the Z-circuit, and after making a few missteps, and replacing some parts that turned out not to be the source of the issue, I eventually discovered that the connections from the IC at location P9 on the PCB to the IC at N9 were being held high when they should be pulsing. The inputs to P9 were were normal, which suggested that P9 (which is a 74LS164) was likely the source of the problem. I removed the IC, soldered in a socket and inserted a new 74LS164.  Happily, this seems to have solved the issue completely.

With that issue fixed, the PCB was now running pretty much perfectly.  The next step was to address the joysticks, which, while functional, also showed some signs they they were in need of some help.

Basic differences between vector (XY) and raster scan monitors:

Vector monitors, also called XY monitors, work on a different principle than standard raster monitors.  Both are CRT monitors, but there is very little similarity beyond that.  Raster monitors, like televisions, create an image by starting at one side of the screen, and scanning all the way across, then moving to the next line, and doing the whole thing again until it gets to the bottom of the display. Once there, it  goes back to the top and starts over. In this way, every part of the screen is active during each frame of video, which is normally thirty frames per second. This is actually very similar to the way film projectors work, by displaying full-frame images at a high enough rate of speed that it gives the impression of movement.

Vectors, on the other hand, work a little differently.  Rather than scanning the entire screen on every frame, a vector monitor actually draws the image on the screen, using only the parts of the screen that are necessary to display the image. The rest of the screen remains un-energized.  Vectors still draw fast enough to give the impression of a persistent, moving image, but they do it using only as much of the screen real estate as necessary.  Here is a simple example of each type of display:

Raster Image

A raster image energizes the entire screen on every frame.

Vector Image

A vector monitor only energizes the parts of the tube that it needs to generate an image.

Vector monitors draw their images using a 3-dimensional coordinate system, X, Y, and Z.

Okay, X and Y make sense, but where do you find a Z-axis in a two-dimensional display?

Here’s the best analogy I have come up with: Imagine you are drawing a picture on paper using a pencil. You are certainly making a 2D image, but if you think about it, you will quickly realize that you are actually working in three dimensions. If not, you’d never lift the pencil off the paper, and every part of the drawing would be connected to every other part by at the very least a line as wide as the point of the pencil.  So in the drawing analogy, you are lifting your pencil from the paper, and a vector monitor does the same thing using the Z-axis. It is how the monitor “lifts the pencil” off the surface of the screen.

The overall effect of a vector monitor is, in my opinion, pretty spectacular, and there is certainly no room for confusion about whether one is looking at a raster or vector.

Centipede Cabaret – Part One – Coming Home

In the hot summer of 2015, I got my first game, a Centipede Cabaret.  For those who may not be familiar with the term, a “Cabaret” is a smaller version of an upright game, often with a smaller monitor, and in the case of Atari, plain woodgrain-patterned vinyl on the sides rather than more elaborate side art.

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Centipede Cabaret, as it sits in my living room as of 2016.

Technically speaking, the term “Cabaret” really belongs to Atari.  Most other manufacturers just called the smaller games “Minis”, or in the case of Taito, the elegant-sounding “Trimline”.   These were games that were probably aimed at locations with smaller spaces, such as bars or small shops, where the smaller size would be a real asset.

Anyway, I had been patrolling Craiglist, which remains a primary source of used coin-op video games, when this nice looking Centipede appeared.  It seemed to be priced about right, and had no obvious flaws that I could see in the ad, so I contacted the seller. We exchanged a couple of texts, and I set off in my pickup truck, along with a pocket full of cash, a hand truck, and my daughter Maile, who was about to turn 10.

On the drive out, I pondered everything that might be wrong with a game, and since this was my first, there was a lot I could imagine, and a lot about which I had no idea.  When we got there , the game was running just like the seller had described.  It needed a good cleaning, some new bearings and rollers for the trackball, and the coin door was pretty beat up.  All of that was okay, though.  We quickly agreed on a price, and Maile and I loaded it up and brought it home.

Once in the house, I could take off the top layer of grime, and see what we were dealing with. The good news: the glass bezel turned out to be nearly flawless. Needless to say, it cleaned up very nicely. With bezel off, I carefully removed the original dark blue monitor shroud, and set to the front of the picture tube with a cloth and some Windex. The amount of dirt and grime on the screen was truly prodigious, and after destroying a couple of cloths, the picture had brightened significantly. It was now apparent that the monitor was really in fantastic shape. The CPO was looking pretty badly stained, but I decided to take a Magic Eraser to it and see what could be done. It brightened almost immediately. There is still some splitting near the bottom of the panel, so it will get replaced at some point, but it’s

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Some cracking along the bend in the control panel overlay.

certainly not a high-priority item.  The carriage bolts holding the trackball in place were badly rusted and pitted, beyond the point of saving, so I found some suitable replacements.

It was finally time to plug the game in and let the family have a crack at it.

In a stroke of luck, it turns out that Julie, the love of my life and mother of my child, is really big on Centipede. She very quickly accepted the presence of a 35 year-old video game cabinet in the living room, which has turned out to be very good news in the time since.

It didn’t take long before I had found a source for new bearings and rollers for the trackball, and got them ordered right away. Now the game play was buttery smooth, just like it was supposed to be.

The coin door was next.  Centipede uses an “over/under” door arrangement, and the lower door had seen some serious abuse.  The edges had been deformed to the point where it wouldn’t close, and there were several spots where the paint had worn through, revealing some noteworthy rust. I spent a few hours in total trying to bend the door back into shape, but never got it to the point where it both looked right and functioned properly.  Also adding the door’s problems was a missing reject button and a mangled coin mech mount.  None of this was a problem for a home use machine, of course, since it had been set to free play within a few minutes of entering the house, but it would never sit right with me until there was a lighted reject button with an appropriate Atari insert.

The solution ended up being a new coin door purchased from a KLOV member.  It appeared to be a few years newer than mine, but I was able to transplant all of the usable parts form the old door to the new, and much more was then right with the world.

Things looked really good for about two weeks, when suddenly something very strange happened:

Something is not right with this G07! Don't worry, though, the image is test mode, but check out the tearing at the bottom.

Something is not right with this G07! Don’t worry, though, the image is test mode, but check out the tearing at the bottom.

The bottom 3 inches or so are missing. That's a problem in Centipede!

The bottom 3 inches or so are missing. That’s a problem in Centipede!

I switched on the game, and while it would start a game, the bottom couple of inches weren’t visible. That’s a pretty big problem for Centipede, since that’s where the player is. Luckily, the KLOV community came through, and in just a few days I had a cap kit and a new flyback in hand, and spent an evening repairing the Elektrohome G07.

After a few hours with the soldering iron, I placed the monitor back in the cabinet. I estimated that there was about a forty percent chance that I would flip the switch and immediately hear a big “pop”, and see that the monitor was now much more dead than it had been before.  I also figured it was just as likely that I would fire it up and see no change. The least likely possibility, in my estimation, was that the monitor would come up looking just like it was supposed to. It turned out that that was exactly what it did.  I didn’t even mess up a solder joint, it just worked, just like it was supposed to.

We celebrated with a family tournament.

I won…