This is another little project which was driven by memories of my growing interest in electronics as a teenager. In the late 70's I built my first ever 'TV game' - from a kit which I bought from Dick Smith Electronics. The 'Stunt Cycle' TV Game kit was based on a design in Electronics Today magazine and was designated ETI-810.

The design was built around a General Instrument IC, type AY-3-8760 which was also the basis of Atari's own 'Stunt Cycle' home console (Model SC-450) whose gameplay closely followed Atari's 'Stunt Cycle' arcade machine. At the time I had never heard of Atari's arcade version or the home console for that matter and now doubt the home version was ever made available in Australia as it would have needed to be re-engineered for our PAL Colour TV system. To this day I have only heard of a few Stunt Cycle arcade machines in Aus. and never seen an actual example.

Even without this background knowledge it seemed like a good idea at the time to build the completed PCB into the side of an old style (timber cabinet) black and white TV - still quite common then as we only went 'colour' in 1975 - putting a bicycle handgrip onto the 'throttle' knob which protruded from the side of the TV. In effect it was quite similar to the original arcade version which I knew nothing of. I even went a step further and came up with a 'Clutch' mod which was really just a resistor in series with the throttle, bypassed by a momentary toggle switch with a lever attached. It was a bit of a 'cheat' which allowed starting, 'wheelies' and 'gear changes' without affecting the previous throttle setting. Even at around age 15 I was already 'hacking' circuits!

Although my original project is long gone - it must have been consigned to Kimbriki Tip with a load of 'old' stuff at some point - the memories came flooding back recently while I was researching early Arcade Machines and Consoles. I was amazed to also find that an eBay seller in the UK still had some New Old Stock of the main component - the exact General Instrument IC for sale. The date code on the IC is from 1978.

Well, that was an offer I couldn't refuse and I even found a copy of the original magazine design article online. The remaining components are readily available apart from the PCB but as the component count is pretty minimal there was no need to etch a copy, the circuit could be easily built on Veroboard.

In a blend of old and new, I built the circuit into the original kit's 'zippy' style box but added a 3D printed 'Marquee' as a tribute to Atari's arcade and console games. Likewise instead of putting the throttle pot on the front as per the original kit, it went on the side, with a 3D printed mini handgrip and of course the 'Clutch' mod added, this time without an extension lever as the game plays perfectly with or without using it.

I left out the RF modulator and speaker, added RCA sockets for AV out and built in a battery holder, in keeping with modern day 'Plug and Play' video games. There is a DC socket on the left side for an external 9V power supply. As per the ETI kit, there are 4 pushbutton switches for game select and the PRO / AM difficulty switch has a centre OFF position to save the battery when not in use.

Even more recently I've discovered that the 'Motorcycle' cartridge PC-502 which was available for the Hanimex / Soundic / Tempest game consoles is the same game using the same General Instrument IC. I now have the Tempest console including 'Motorcycle' and other game cartridges. The Tempest console combines the picture elements in colours similar to the Atari home console rather than shades of grey as per the ETI kit but is otherwise the same.

I actually prefer the black and white image generated by the ETI design, with no colour encoder. It more closely resembles the original arcade machine which was also monochrome. On the arcade machine however the motorbike travelled from right to left on the middle row and there were some overlays stuck on the face of the screen which looked like curved pipes, to appear as if the bike entered the tube at the end of each row, emerging on the next.

Web Resources -

Motor Cycle Stunt Game - Dick Smith Electronics Ad

Atari Stunt Cycle (1976) - YouTube

ARCADE USA - Game Spotlight - Atari's Stunt Cycle - YouTube

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