The VCF ELF


Build A Classic COSMAC ELF Microcomputer
at the 2016 Vintage Computer Festival Midwest


The August 1976 issue of Popular Electronics magazine had a breakthrough project on the cover. "The COSMAC ELF: A microcomputer trainer that's powerful, expandable, and costs as little as $80." (Click on the magazine cover to read the original article.) To put this in perspective, the Apple I was selling for $666.66 at the time; and the Apple II didn't even exist yet!

The ELF truly was a simple inexpensive computer. Thousands of people built it (including us!). In the process, we learned about computer hardware and software right from the ground up. This experience is largely lost today, when everyone simply buys everything already built and programmed for them.


The Plan

This is the 40th anniversary of the ELF. In honor of the occasion, we decided to recreate the original ELF for the Vintage Computer Festival Midwest in Chicago IL on September 10-11, 2016. To give people a "taste" of what it was like, visitors to our booth had all the parts and tools needed to build a real COSMAC ELF. This was a wire-wrap project -- no soldering at all! We showed folks how to wire-wrap, so by the end of the show, participants had almost finished a complete vintage computer from scratch.

This computer was then raffled off. Everyone who added at least one wire got to put his name on a raffle ticket. At the end of the show, we drew the winning ticket out of a hat. One lucky builder won a FREE genuine hand-crafted COSMAC ELF computer!

The photo is our 40th anniversary recreation of the original Popular Electronics Elf. Click here or on the photo for a movie of the VCF-ELF in operation.

Links

Parts

By pooling our resources, we had enough parts to make four kits; so that was the "production run". It's ONE for the money (auctioned off at the show with the proceeds donated to VCF-MW11); TWO for the show (the one built at the show and raffled off); THREE to get ready (Chuck built one to test and demonstrate that it all works); and FOUR, I don't know (we gave it to Dave Ruske, who sold it on eBay to provide funds to support the www.cosmacelf.com website). :-)

Here's the VCF-ELF parts list, in case you want to build one for yourself. We used premium vintage parts wherever possible to keep the "look and feel" of the original; but there are lots of cheaper alternatives if you're on a budget.

VCF-ELF Parts List
QTY
ID#
Description
2 C1,C2 10uF 16v X7R ceramic capacitor (digikey.com 445-2887-ND)
4 C3-6 0.1uF 25v X7R ceramic capacitor (jameco.com 25523)
3 D1,D2,D51N4148 signal diode (jameco.com 36038)
2 D3,D4 1N4001 50v 1a diode (jameco.com 35975)
1 IC1 1802 microprocessor (alltronics.com CDP1802ACE)
2 IC2,IC3 5101 256x4 RAM (jameco.com 42198)
1 IC4 74C374 or 74HC374 octal latch (jameco.com 44409)
1 IC5 4071 quad 2-in OR gate (jameco.com 13274)
(2) IC6,IC7 (optional) hex display, TI TIL311 (bgmicro.com LEDTIL311) or HP 5082-7340 (rcfreelance.com 5082-7340)
2 IC8,IC9 4016 quad SPST switch (jameco.com 12722)
1 IC10 4023 triple 3-in NAND gate (jameco.com 12845)
1 IC11 40106 hex schmitt-trigger inverter (jameco.com 893179)
1 IC12 4013 dual D flip-flop (jameco.com 893443)
9 LED0-8 LED red T1-3/4 (jameco.com 2125309)
1 P1 header 12-pin (2x6) wire-wrap (digikey.com H123890-ND; cut in thirds)
1 P2 header 40-pin (2x20) right-angle wire-wrap + 2 ejectors (digikey.com CHA40G-ND + CLKS01-ND or CLKS02-ND)
1 R1 100K x 9 10-pin SIP resistor bussed (digikey.com 4610X-1-104LF-ND)
1 R2 1K x 9 10-pin SIP resistor bussed (digikey.com 4610X-1-102LF-ND)
1 R3 5Meg trimpot (digikey.com 3296W-505LF-ND)
1 R4 1K 5% 1/4w carbon film resistor (jameco.com 690865)
12 S1-11,13switch SPDT submini toggle PC pins (C&K T101LTCQE or Wonderco ebay #140741190973 2MS1T1B7M2QE)
(optional) toggle switch vinyl caps (white digikey.com CKN10598-ND, red digikey.com CKN10599-ND)
1 S12 switch SPDT submini pushbutton PC pins (onlinecomponents.com TP12LTCGE)
1 XTAL 1.8 MHz ceramic resonator with capacitors (Tayda Electronics ebay #321044248918)
1 40-pin wire-wrap IC socket (jameco.com 94503)
2 22-pin wire-wrap IC socket (semisurplus ebay# 321201622119)
2 20-pin wire-wrap IC socket (jameco.com 38632)
1 18-pin wire-wrap IC socket (jameco.com 94482)
6 16-pin wire-wrap IC socket (jameco.com 37411)
(2) (optional, for TIL311) 14-pin wire-wrap IC socket (jameco.com 62051)
(1) (optional, for 5082-7340) 24-pin wire-wrap IC socket (jameco.com 105372)
1 5.25" x 6" perfboard with holes on 0.1" centers (jameco.com 206594)
2 wood side supports 6" x 3/4" x 1/4" (home-made)
6 #4 wood screws to attach side supports
1 battery holder 3-AAA cells (jameco.com 216303)
1 2-pin connector for battery holder (jameco.com housing 234704, pins 234931)
40' approxwire-wrap wire, stripper, and wire-wrap tool (jameco.com, digikey.com, and many sources on eBay)

Changes from the original

The first illustration shows the parts placement on the front side of the board. The second is a paper template, to label the controls and provide pin numbers on the back to make wire-wrapping easier. The last picture is the finished prototype, all wire-wrapped and working. How's it look? :-)

It could have been built EXACTLY like the original. An exact copy would appeal to historians; but not to the average person today. Some parts are also rare and expensive, and no clear expansion path was provided. Therefore, a few changes were made to be cheaper, easier to build, and more useful in the modern world. Also, because Lee has engineer disease and can't resist "improving" things. :-)

Credits:

The VCF Elf project would never have been possible without generous donations of time and materials by Lee A. Hart, Josh Bensadon, Ed Keefe, Dave Ruske, Walter Miraglia, Chuck Yakym, Bill Rowe, and Norm Nelson; and to our many advisors and volunteer builders. A hearty THANK YOU to everyone that helped to bring this delightful project to completion.

Lee Hart




Last update 10/12/2016.
Go to TOP ........ Go to HOME ........ Questions? Comments? Email me for details.
Web hosting provided by Turtlehut Internet Marketing http://www.turtlehut.com/