I have been working to repair and once again enjoy the vintage Intellivision video game console – and I’ve largely succeeded!

Read on for more:

Background

Some people grew up playing the Nintendo Entertainment System. Others grew up with the Sega Genesis or Nintendo 64 or Gamecube or Wii. Some had a version of the Xbox or Playstation or something else.

I grew up with the Intellivision from Mattel Electronics. Or, more precisely, we had the Sears version of the console called the Sears Tele-Games Super Video Arcade.

Debuting in 1979, the Intellivision was simply the best home video game console on the market at the time. Sporting the General Instrument chipset (including the 16 bit CP1610 CPU), it provided, as Strong Bad might say, “a spectacle of graphics and sound!” The system was capable of an amazing resolution of 160×96 pixels, and the sound hardware could produce three channels of incredible sound. Early games fit into cartridges with 4 kilobytes of ROM, while later games supported more. A later addition (Intellivoice) added speech capability.

The controllers were unique: a directional disc was at the bottom, with side buttons each on the left and right, and a full, 12 digit number pad dominating the centre of the controller. Games included plastic overlays that could be placed over the number pad, giving a better indication as to what the different buttons did in the game.

To be sure, while the specifications of the Intellivision were superior to the Atari 2600, they are not tremendous by modern standards. To me, that doesn’t matter. When programmers had a whopping 4KB of ROM space to work with, they had to concentrate chiefly on one aspect of the game: making it fun!

And the games largely succeed! The console is focused mainly at two player games (after all, it’s hard to code artificial intelligence in 4KB!), and so many of those games are utterly addictive. Frog Bog is a calming experience of high level of replay-ability, with games lasting only a few minutes each. Auto Racing and Skiing are high-speed fun with smooth-scrolling, top-down graphics (not much 3D is possible in 4KB!). Baseball is iconic, with just the right amount of difficulty (“YER OUT!”). And Biplanes, part of the Triple Action cartridge, is perhaps the most two-player fun I’ve had on a video game console. Period.

Several single player games are also incredible. These include everything from Night Stalker and its haunting thump-thump-thump soundtrack, to the Pacman-esque Lock ‘N’ Chase, to Masters of the Universe (which really showcases what the hardware is truly capable of creating). The console is focused on fun, and it delivers!

The Project

As mentioned, we grew up with the Sears version of the console. Unfortunately it had developed definite problems: the graphics glitched in very strange ways, games sometimes crashed outright, and the controllers were broken.

Back in the early 2000s I sought to rectify this: I found a used INTV version of the console for $35 on eBay. It was labelled “INTV System III” and was produced by INTV, which bought the Intellivision rights from Mattel in 1984. It’s essentially an original Intellivision with some minor cosmetic differences: even the circuit board contains the same, hand-drawn traces.

The new unit worked! Briefly. But while it worked it was fun to play. However, unfortunately the graphics began to also glitch out and the controllers became less and less usable. This console was, sadly, forced into retirement. However, I had always wanted to revisit the console and see if I could get at least something working again.

Repair attempt #1

Since we had two models of the console – the Sears and the INTV units – I was hopeful that perhaps I could cobble parts together from both units to produce one functional device.

It turned out to be a fair bit more difficult than that, but I’ll get to that further below.

Thankfully there are a number of sites and user forums where people have been sharing their own knowledge of the hardware and their repair attempts. I suppose this blog post can be seen as an addition to those sites. So, I had some starting points. I also have my degrees in electrical engineering and computer science and those were definitely put to use in some of the troubleshooting.

So, which console would I attempt to repair? The Sears unit was our family’s original and has by far the most sentimental value. However, it turned out that the controllers would be the deciding factor: the custom, detachable cables on the Sears model were wrecked and I would need to figure out how to source something new with the same number of conductors, as well as the matching DB9 connector that would fit into the plastic ports on the Master Component. On the other hand, the INTV unit did not use detachable controllers, but overall they appeared to be in much better shape with fully intact wires. Thus, I decided to attempt to repair the INTV console.

Disassembly

Thankfully, the Intellivision Master Component (the name of main console) was very easy to disassemble. There are six Philips screws on the bottom and the two halves of plastic come apart. Six more screws hold in a long, plastic piece that keeps the mainboard and controller cables in place. The controller cables themselves are attached with simple connectors, so it’s really easy to remove those.

The mainboard was covered by a (very dusty) metal RF shield. That needed to be removed to have any access to the chips. It took a bit of time, but my soldering iron and some solder braid worked fine.

There was also a little ribbon cable connecting the power supply to the mainboard that needed to be disconnected. I’ll have more on that below.

The Controllers

Given that the controllers drove my decision to attempt to repair the INTV unit, tackling the problems with those controllers was the first thing I looked at. While I figured I could repair the board (sourcing replacement parts is quite possible on eBay), unless I could get those somewhat-finicky controllers working it would all be for naught.

Unfortunately the controller design is entirely custom for the Intellivision: it’s based on mylar sheets coated with conductive material in just the right locations, and contact points for making electrical connections with the cables that return to the console. With the controllers that I already had on hand, these mylar sheets had either become broken from heavy use or were so corroded that the prospect of repairing them was daunting.

Thankfully, someone in the UK was having a similar problem and started to produce replacement mylar sheets! And they weren’t horribly priced, either (though shipping from Europe was the highest part of that cost). I ordered several and attempted installation. It took a few tries (did I mention how finicky the controllers are??), but I eventually found success! I have two working controllers!

It somewhat cracks me up that I thought this would be the most difficult part of the repair but it was one of the easiest.

The Power Supply

Another common problem with the Intellivision consoles is the power supply. Thankfully the supply on the INTV worked fine, producing the proper voltages in a stable way. The voltages themselves range from normal, regulated voltages for (+5V and +12V), to stranger, non-regulated voltages (+16V, +5.65V, and -2.1V).

So, the power supply worked. The capacitors (which can be a common failure point) looked good also. What wasn’t so good, however, was the ribbon cable that connected the supply to the mainboard. Frankly, it’s about as cheap as could be imagined: metal traces on plastic. These are enormously fragile, especially after several decades. So I thought it would be opportune to replace the ribbon with proper wires. I managed to find the correct, five-pin connector at a local electronics store and soldered wires from that connector directly to the mainboard. That was an easy fix and makes it much easier to detach the cable without destroying anything else.

Graphical Glitches

The largest electrical/logical problem I saw with the console were the random graphical glitches that happened with pretty much every game. Sometimes sprites would be duplicated (sprites = graphical characters/units that move around — think of something like Mario on the old NES, which is composed of sprites). Often the sprites had weird glitches and looked completely wrong. Other times the collision detection failed: that is, when two sprites collide (say, two planes in Biplanes), the game wouldn’t register the collision. Other times collisions were registered when two sprites were nowhere near each other.

Step 1: Reseat all the chips, clean contacts, and reflow solder

The easiest step to try when strange glitches happen on these old systems is to reseat all the socketed ICs (integrated circuits — microchips). The idea is that sometimes corrosion or bad contacts can cause strange things to happen. Thankfully the Intellivision makes this easy for the largest chips. By gingerly using a small, flat-head screwdriver I was able to remove each IC, clean the contacts with some alcohol and contact cleaner, and reinsert each chip.  Unfortunately, nothing changed.

I also cleaned the contacts in the cartridge port, as a dirty port can cause odd glitches. This is actually a very common point of failure on the original Nintendo Entertainment System! Many people try blowing on the cartridge to get a game to work, but what they are most likely doing is twofold: cleaning dust from the contacts and, by reinserting the cartridge, possibly removing some corrosion on the contacts. The best solution is to carefully clean the contacts. Use some 99% isopropyl alcohol and cotton, and, better yet, a proper contact-cleaner spray such as Deoxit.

Unfortunately for me, this did not solve the problem.

The last thing I tried in this step, which is much more tedious, was to reflow the solder on all the parts on the board. Looking at the board, it seemed that a lot of the solder had become old and brittle and I couldn’t trust that it was still maintaining good contact everywhere. So, I touched up every solder joint on the underside of the board.

While none of this solved the problem, it has hopefully helped this board last longer. But I still needed to figure out the source of the issue.

Step 2: A STIC-ky problem

All of this pointed to one big problem: the STIC chip was failing. STIC stands for Standard Television Interface Chip, which in the Intellivision is the General Instrument AY-3-8900-1 chip. These are a common mode of failure for the Intellivision and seem to be getting harder to find.

My first thought was to try the STIC chip from the Sears model I already had. Amazingly, this actually worked! Briefly. It became apparent that the chip was rapidly overheating and that’s when the issues would arise. Even though the STIC comes with a very basic metal heatsink, I added a few more small heatsinks sourced from Amazon. It improved the length of time before I would experience problems, but it did not ultimately solve the issue. It did, however, confirm that the STIC was definitely the source of the graphical glitches.

So I looked online for a replacement. Some places in China claimed to sell the chips but my search coincided with the spread in China of the this little-known virus called COVID-19. Shipping from these companies was basically shut down.

I found a place on eBay in the USA that sold a STIC removed from another console for cheap. Sadly, it also had some glitches — the problems looked slightly different from the other two chips, but they were definitely there.

Finally, I found someone selling an as-is Intellivision II on eBay. It had no power supply and no guarantee that it worked. But since it was a newer, cost-reduced version of the original Intellivision, the Intellivision II contains a lot of the same chips as the original console. And the eBay listing was cheap enough that it was worth a try.

That console arrived quickly and, amazingly, the STIC from it works perfectly! The graphical issues were completely resolved! I added a some heat sinks to the chip to (hopefully) help it last much longer.

Composite Video Modification

There was one other thing I needed to do. The Intellivision’s only audio/video output is through an old-style RF connector. Essentially, to use it you need a television with an analog RF jack and a special antenna switcher box. Once the television is tuned to channel 3 or 4 you get an image and sound. Unfortunately this is prone to noise in the signal, and modern TVs don’t have the appropriate analog RF jack.

Thankfully, there are instructions online for adding a composite video and line-level audio output to the Intellivision. You can either order the parts and assemble it yourself or buy a pre-made board and follow the instructions. This does require drilling some holes in the case for the RCA-style connectors, but it’s well worth it.

As a side effect, the video is definitely sharper than what is possible with the RF connector! Mine may have some adjustments that could be made for colour bleed, but I think it’s generally good enough and it definitely looks much better than it ever has.

Enjoying the Console

I now had a working INTV-model Intellivision!

Almost.

Unfortunately, this was right around the time of the COVID-19 shutdowns in Canada. Since the console is best played with two players, I couldn’t exactly put it through its paces for a while. And once things started opening up again I became as busy as I’ve ever been: the parish re-opening was enormously complex. Further, I was given new responsibilities in the diocese and I started graduate-level classes in canon law. The following year, I moved. Twice. Finally, once in my new parish I was able to connect the console and give it a good workout.

Unfortunately, not all was well.

Repair attempt #2

Basically, the console was crashing/freezing. There were some patterns to the freezes, though sometimes it was quite random.

I found I could get the console to freeze every time while playing the Skiing game: if my player crashed on the way down the hill, the whole Intellivision would freeze when I reached the bottom and the people started cheering. If I did not crash, the Intellivision would work fine. That was … curious.

Other games seemed to crash at definite transition points during the gameplay. For example, if I was about to reach the “Game Over” state in Space Armada, the Intellivision would freeze just before displaying my final score. After scoring a goal in NHL Hockey it would also sometimes freeze.

That led me to wonder about several things: the cartridges themselves, some RAM or ROM, or the CPU.

The Game Cartridges

The Intellivision cartridges contain ROM chips that are mapped to certain locations in memory. What’s particularly fascinating (and unusual) is that, while the CPU is a 16 bit device, the instructions are 10 bits wide. This apparently makes the game cartridges much less straightforward to modify or create than they might be with something like a Commodore 64, where the CPU is a basic 8 bit unit and addresses memory accordingly.

Nevertheless, I had nothing to lose by ensuring the cartridges were clean. I also found someone on eBay selling a very cheap Skiing cartridge ($6 shipped), so that was worth a shot.

Unfortunately this did not solve the problem.

RAM or ROM

I’m putting on my engineering/computer science hat for a moment here. Essentially, a console’s memory will contain a number of things: everything from data for the game (scores, pieces of information about the onscreen characters, etc), to the actual code that the computer executes to make the game happen.

Given that the crashes occurred right when the state of the game changed — either the end of a ski hill, or a goal was scored, or just before the “Game Over” screen, I wondered: was there possibly part of the RAM or system ROM that was corrupted?

I thought about swapping some of those chips. But then I found an original Mattel Electronics service manual online.

CPU

The service manual (linked here) actually anticipates a lot of these problems. And it helpfully gives ideas of which chips to replace and in which order.

The first chip it suggests replacing for the random issues I was having was the CP1610 CPU. This also makes sense, from an engineering point of view. Different parts of the chip are responsible for different instructions that a game runs. Perhaps the part of the CPU that runs commands related to changing the state of the game — maybe something about jumping from one part of code memory to another — was flaky.

Well, as you can probably tell from above, I helpfully had two extra CPUs on hand: one was from the old Sears Super Video Arcade, and the other from the Intellivision II. I thought it would be neat if some part of the old Sears console was still in use; so I carefully removed the CPU from the older Sears model and put it into the INTV unit, and gave it a test.

IT WORKS.

PERFECTLY.

The CPU in the Sears model has a date code indicating it was made during the 30th week of 1980.

And it freaking works.

!!!

Conclusion (Maybe)

So I now have a working INTV System III Intellivision!

I’ve been using it for a few days and it seems to be rock-stable, just as I remember it in the 1980s.

Thankfully, I also have two parts units that can be used if anything else fails (unless it’s the STIC, as I now have four of those chips but only one that works!). Alternatively, if I can source another working STIC and replacement cables, then perhaps I can also get the Sears unit working. The Intellivision II doesn’t run all of the games due to a change in the ROM, so I’ll probably leave that as a parts machine.

Who wants to play some vintage video games?