My old vintage Electronics Hobby Photos
In the mid 1970’s, during my teen years, my interest in electronics resulted in my building of a totally “home brew” computer. It was based around the RCA 1802 microprocessor. I started with a basic circuit diagram as published in “Popular Electronics” magazine, who referred to it as the Cosmac Elf. I wanted something “fancier” than the open breadboard type of circuit, so I designed mine based loosely around the IMSAI 8080 that I had seen in magazine advertisements.
Cosmac Elf 1802 home made computer, 1975
![](https://yesretired.com/wp-content/uploads/2023/12/nggallery_import/Elf1-1024x765.jpg)
It featured eight on/off input switches (7-0) to set the binary data input of HEX digits. Plus a 2 digit HEX display (0-9, A-F). Also 4 special EF input switches that could be set to control other devices
1K MEMORY BOARD, home made
![](https://yesretired.com/wp-content/uploads/2023/12/nggallery_import/Elf2.jpg)
The circuit board shown here was an evolution of the original 256 Byte design, adding 1024 more bytes (1K). I used a kit from Radio Shack to etch the copper backed circuit boards, using my own designs, based on the schematic.
My interest in electronics was spawned at the age of 8 years old, when my dad showed me how to build a home brew “Crystal Radio”, using a 50 foot long copper wire as an antenna, a toilet paper roll coil, cat whisker diode, and headphone set from his dad.
![](https://yesretired.com/wp-content/uploads/2023/12/nggallery_import/CrystalRadio2.jpg)