The lost transistor?

The lost transistor?


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.

16 thoughts on “The lost transistor?

  1. UptownGreen says:

    An important distinction needs to be made here- the Bell labs folks didn’t invent the first transistor, they invented the first bipolar junction transistor.

    The functionality of the transistor was well understood by then- what the guys at Bell did was to make a semiconductor device that did it.

    1. Collin Cunningham says:

      Thanks much for the insight!
      I was referring, in particular, to the point-contact device constructed by Walter Brattain and John Bardeen – not William Shockley’s Bipolar Junction Transistor which was developed subsequently. However, there does still stand a fundemental difference between Brattain&Bardeen’s device in comparison to Adams – the former apparently utilizes 2 layers of doped semiconductor, while the latter apparently only uses the raw crystal.

    2. bill beaty says:

      Yay! I’d heard about that “two-whisker detector,” but never found anything online about it.

      One issue: if the whiskers are too far apart, or if its bias polarities are wrong, then it’s not a transistor, but instead is just a battery-biased rectifier (with zero Vf turn-on voltage, so it picks up much weaker signals.) I know the old amateurs had battery-biased detectors, but they applied the voltage to the two terminals rather than having a transistor-like device.

      I found an old book of conference papers on the Bell Labs transistor discovery, and one of the papers was about making cats-whisker transistors from Galena. Very useful for anyone attempting this.

      The experimenters found that in order to see some gain and start “transisting,” the whisker-tips had to be spaced far closer than 0.1mm. They also found that it only worked using freshly-cleaved Galena surfaces, and humidity would spoil the transistor effect after awhile. Also, they found that they first had to obtain a good, reliable base-emitter diode, but after that most any crude collector-base contact would give transistor action. Apparently it’s not necessary to find TWO close-spaced hot spots on the crystal, only one. Finally, they created extremely sharp whiskers by dissolving the ends using electrolysis. I’ve seen this done for STM… the etching at the water surface will eat the metal faster, so when the submerged part breaks off, yank the rest out of contact with the bath.

  2. Vladimir says:

    … they were sold in Mexico in kit form by a company that sold all kinds of science toys. This was almost 20 years ago, I wonder if they are still in business, they were called “Myalegria” which means something like “my joy”.

    I can’t remember many details but it was very simple, it shouldn’t be difficult to make one.

    Anyways, Google can’t find anything about Myalegria, I wonder if they really existed…

    1. Collin Cunningham says:

      Do you mean a basic crystal radio set?

  3. DV82XL says:

    If you look in the PW Crystal Experimenters Handbook of 1925 (link below)

    Not only will you find descriptions of amplification with ‘radio crystals’ but the odd oscillator circuit as well.

    It would seem that these effects were well known, at least in amateur radio circles.

    1. Collin Cunningham says:

      Awesome – thanks for the link!

      I was aware of some references to crystals used by naval electricians as oscillators, but not specifically for amplification

    2. DB says:

      I love finding old technology articles like this. Thanks for posting the pdf link.

  4. Dave says:

    Do a search on Oleg V. Lossev (and variations, such as “O.V. Lossev”). He had a solid state amplifying device in the 1920s/30s. Unfortunately, he seems to have disappeared in the Battle of Stalingrad (probably, literally, in a flash). :-(

    There is also some evidence that Greenleaf Whittier Pickard invented what would become the tunnel diode, as reported in QST magazine, March, 1920, page 44 (members only):

    There are also anecdotal stories of three terminaled “crystal diodes” that produced amplifying action even earlier. Could some of these people have discovered what would become the point contact BJT?

    There is also a Yahoo group devoted to home produced transistors, and which references a “Practical Wireless”
    article from the 1950s on how to make a transistor at home:


  5. anachrocomputer says:

    There’s a very good book on the subject of the invention of the transistor: Crystal Fire by Michael Riordan and Lillian Hoddeson. They mention that part of the reason why Bell Labs pressed ahead with the patents for the bipolar transistor was that the earlier patent (1920s) covered the field-effect transistor, and would have been considered “prior art” for the FET. Development of the FET then happened later, after the initial work on junction transistors, first in germanium and later in silicon. The book also describes how the researchers at Bell Labs first understood the physics of the transistor, and hence the need for extremely pure germanium and silicon. The innovative method of “zone refining” was a crucial part of the technology of semiconductors.

  6. Hiro Protagonist says:

    This guy documents some interesting modern-day experiments with homebrewing unconventional amplification and negative resistance devices, such as zinc oxide based amplifiers, and even an alcohol-flame triode:

  7. Gareth Branwyn says:

    This is a great, Collin. I want to do an installment of my Lost Knowledge column on experiments in making your own electronic components, inspired by your LED video. So, if anyone has decent links to homemade Leyden jars, tunnel diodes, triodes, homemade transistors, coils, condensers, conductors, etc., post ’em here.

    Does anyone have Pete Friedrichs’ book Voice of the Crystal? Is it any good? I’ve tried emailing him several times and never heard back. The images on his website are amazing:

    1. HP Friedrichs says:

      To Gareth Brandwyn:

      Gareth, I’m always glad to hear from fellow experimenters, so I answer *all* emails. If I didn’t answer you, it’s only because I didn’t get your messages.

      Truth be told, I have had some problems in recent months with my ISP interpreting incoming emails from certain domains as spam. You can reach me through the email address on my web site. If that doesn’t work, you might try sending from a different mail account.


      H.P. “Pete” Friedrichs

  8. nad says:

    Though Dr. Robert George Adams passed away in 2006, his website documents some of his work

    Sadly it seems that the content on Adams website had been erased and that the website had been taken over by some ad company.

  9. vortrus | Alternative Inputs says:

    […] first sound, considering that, as Jordan points out, his experiment is actually “based on the Adams Crystal Amplifier (1933), a precursor to the modern transistor, one of the fundamental building blocks of […]

  10. Lost Knowledge: Homemade electronic components | Make: DIY Projects, How-Tos, Electronics, Crafts and Ideas for Makers says:

    […] The Adams Crystal Amplifier (1933) From Collin’s post: […]

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