While conducting historical research for the recent MAKE presents: The Transistor video, I came across references to an earlier iteration of the device apparently created way back in 1933 – a full 14 years before Bell Labs researchers had a working model. What makes the discovery even more compelling and inspiring is the fact that its inventor, Robert Adams, was only 13 years old when he made it. Though no patents or publications were created describing its functionality, Adams is said to have built multiple crystal radios utilizing the device. Though Dr. Robert George Adams passed away in 2006, his website documents some of his work –
Two different methods of interconnection between the two crystals were employed –
1. By copper wire from a crystal mounted in a crystal cup, the other end of which is connected to the crystal set proper.
2. By direct physical contact (under small pressure) in an assembly of two crystal cup holders with vertical mounting brackets secured to a small insulated base board.
Connections to this small module of two crystals was achieved with the use of the then available vertical cantilever type cats whisker holders, providing stable connections to the central junction and input and output points. The words ’emitter’, ‘base’, ‘collector’ hadn’t yet been born for this new device, which, of course, was destined to become known today as a “transistor”.
Inspired by Adams’ story and my experience building a homebrew LED, I’ve begun experimenting with carborundum to create my own point-contact transistor. As I’m sure readers out there have more experience in the field of crystal detectors and similar, I’d love to hear of any ideas/experiences/opinions regarding DIY transistors in general – be sure to share any you may have in the comments below.