LED retrofit for vintage edge-lit numeric display modules


This single digit display is an old edge-lit module that [Ty_Eeberfest] has been working with. The modules were built for General Radio Company and have a really huge PCB to control just one digit. [Ty's] modules didn’t come with that driver board, so he was left with the task of controlling an incandescent bulb for each digit. After a bit of thought he figured it would be much easier to just replace the edge-light bulbs with a set of LEDs.

We’ve seen these exact modules before, referenced in a project that created an edge-lit Nixie tube from scratch. Each digit in the display is made from a piece of acrylic with tiny drill holes which trace out the numerals. The acrylic is bent so that the edge exits out the back of the module where it picks up light from the bulb. [Ty] laid out his circuit board so that each LED was in the same position as the bulb it was replacing. As you can see, his retrofit works like a charm.

[Thanks Brian]


  1. Hirudinea says:

    Very nice, not only did he resurrect the display he made it better, this is what hacking is.

  2. Haku says:

    I hate the partial article setup on the front page of HaD, please put back the whole articles.

  3. soundman98 says:

    does anyone have any info about how these displays channel the light to illuminate the digits? the layout isn’t making sense to me, but it obviously works perfect…

  4. Larry Ng. Resistant, HAD. says:

    Edge-lit displays may be interesting and cool and steampunk and everything, but they are NEITHER NIXIE NOR TUBES.

  5. Franklin Templeton says:

    At first I went the usual HaD route of wtf man but after reading the article have arrived at “Kudos, Man!” Definitely an interesting read. Keep on tinkering :)

  6. geekmaster says:

    Awesome! I have a bunch of these with tiny “grain of wheat” incandescent lightbulbs in them. Although I also have a supply of such replacement bulbs, I like this energy-saving replacement!

    • geekmaster says:

      I also have a bunch of older vintage displays that have a ground-glass front surface, and each lightbulb is covered by a transparent digit mask and a lens, They rear-project digits onto the front surface. I should be able to upgrade them the same way as these. Now I have a reason to dig them out and use them in some “steam-punkish” contraption. :-)

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