Sunday, January 5, 2014

Building the Micro Chroma 68 Kit

The Retrochallenge Winter Warmup 2014 event started days ago, and I have yet to blog about my entry!  I guess I need to get going on that... :-)

For some time, I've been in possession of a mostly complete Micro Chroma 68 kit that I acquired from someone in the Tandy Color Computer (CoCo) community.  Over time I've acquired most of the parts required to build the kit, and I've been on a bit of a roll lately with electronics construction projects.  So, I guess this is as good a time as any to work on this build!

What Is It?

The Micro Chroma 68 is a single board computer (SBC) based on a derivative of the Motorola 6800 processor.  It was produced as a platform for demonstrating the Motorola 6847 video display generator (VDG).  Along with the amazing graphics capabilities of the VDG, the Micro Chroma 68 features an interface for loading and storing information stored on audio cassettes, and a keyboard interface for interacting with the device as a video terminal.  The device also features an EXORcisor bus connector for interfacing to other devices.

I have seen it suggested that this device provided some inspiration to the designers at Tandy that ultimately produced my beloved CoCo.  Whether that is true or not, it seems likely that those designers would at least have been aware of this device.  While the Micro Chroma 68 is clearly designed for engineers and experimenters, it does show the first few steps toward producing a standalone computer consumable by normal folk.

The Micro Chroma 68 also seems comparable to the venerated Apple I design.  They certainly have similar features and capabilities.  Given the high cost of building even a replica Apple I kit, this is probably the closest I'll ever come to that experience!

Shop 'Til You Drop

The Micro Chroma 68 kit comes with a printed circuit board (PCB), and a handful of key integrated circuits (ICs).  However, it is far from a complete kit and not all of the other parts are still commonly available.  I had made a point of acquiring most of the remaining ICs already, but some of the other parts are equally hard to find.  Luckily, some strategic eBay shopping and a check of a trusty electronics surplus provider (Unicorn Electronics) seems to have located all of the required parts.

Unfortunately, I didn't do this shopping until New Year's Day.  Some of the items are coming from distant suppliers, and I may not have everything in hand until the third week of January or later!  Hopefully I can make enough progress with what I already have and anything that comes early so as to still have a chance to complete the build....

Other Pursuits

I had some time-off around the turn of the new year, and I used it to work on a variety of retro-ish hardware projects.  I fixed old game consoles (even a Vectrex!), made cables, built circuits, and even made a project enclosure out of an old cigar box!  Anyway, I've got a lot of distractions available to keep me busy even if the Micro Chroma 68 parts get delayed.  If that happens, then I'll try to at least post a link or two here as well.  In any case, be sure to stay tuned... :-)

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