An ELF!

Way back in the days when most microcomputers were beyond the means of all but the most dedicated hobbyists, Popular Electronics published in its August 1976 issue an article entitled 'Build the COSMAC "ELF": A Low-Cost Experimenter's Microcomputer'.  If you're not lucky enough to have that issue, you can read Bill Richman's scan of it. (local mirror)

The Front Side.  It's pretty close to the original (Part 1) ELF.  I do have an 1861 video chip as was used in the revised (Part 4) design, but I wanted to build the original version. Originally I had used a laser-printed front panel, but members of the cosmacelf mailing list pointed me at a source of dry-transfer letters,  so I redid it the authentic way (Detail of switches and panel lettering).  Another nice thing that happened after I first built it was that I located some authentic RCA CMOS logic ICs for a number of the types used in the ELF.

The differences in this rendition from the original are:

1. I couldn't find an LM309 regulator in this package, this one is an equivalent 7805;
2. I used new composition resistors as available from Mouser; but I found some nice old ones at a surplus store that will work

Here's a close-up that shows exact parts placement I used. This layout was arrived at by starting with the article picture and then placing the parts where the wiring made the most sense. If you intend to use an 1861, now's the time to make room for it!

Here's a template for cutting and drilling the aluminum switch panel in BMP format at 300 DPI.

The Back Side.  Construction is wire-wrap throughout.  There is no photo of the original wiring, but I suspect that it was a point-to-point mess, perhaps using a wiring pencil.  Here the ICs are in WW sockets and the small components are soldered to posts.  It ran the first try!

Component Sources