In retrospect, it’s been a funny old day with respect to retro displays and computers, starting with Numitron tubes (which use seven incandescent filaments arranged to form a seven-segment display) and ending with an 8-bit computer implemented using 1950s thermionic valves (vacuum tubes).

Now, I want you to be honest with me… am I alone in loving the technologies of yesteryear? For example, is it just me, or do you also feel that older display technologies have a soupçon of style coupled with a modicum of gravitas?

The reason for my meandering musings is that, earlier today as I pen these words, my old friend and fellow contributor here at EE Journal, Steve Leibson, sent me an email with the subject line: “This video on display tech is right up your alley…”

All I can say is that Steve certainly knows how to grab my attention. When I opened this email, I found a continuation to Steve’s missive, which—in its entirety—read as follows: “This video on display tech is right up your alley… although the smarmy attitude from a Millennial and heaps ‘o misinformation is bound to chafe” (don’t talk to me about chafing, but that’s a topic for another day).

This was accompanied by a link to a YouTube video with an intriguing title: The Numitron: An Obvious Idea That Wasn’t Very Bright. Ha! A display technology that’s not very bright (I do love a good play on words).

Steve is correct, this video is not without its problems. It’s also not without a sense of humor. I must admit I love the presenter’s deadpan style when he says things like, “This is what I can only describe as the crudest possible way to produce a technically functional 7-segment display for digital devices.” In fact, I’ll go so far as to admit to having a couple of “laugh out loud” moments.

I also like the fact that the presenter covers a lot of ground in a short period of time. For example, he’s one of the few people I’ve run across who mentions the 21-segment display conceived by George Lafayette Mason circa 1898 (see also my column Recreating Retro-Futuristic 21-Segment Victorian Displays). Also, he gives a nice introduction to the vacuum fluorescent displays (VFDs) I’m using in the latest incarnation of my Countdown Timer project (see also my column My AI Will Be Watching You).

It must be acknowledged, however, that the presenter does seem to have something of an axe to grind when it comes to Numitron tubes and their creators at RCA. It’s hard to determine which he dislikes and disparages the most.

On the one hand, I tend to the view that any 7-segment display is a good 7-segment display. On the other hand, the presenter is not wrong in his Numitron tube criticisms. The designers of this device do seem to have made more than a few dubious implementation decisions.

I circled back with Steve to ask if he would be kind enough to summarize his criticisms of the video, and he responded as follows:

Right off the bat, this guy thinks microprocessors preceded these displays. That’s a typical mistake for someone born long after microprocessors made the scene. Younger people today feel like there have always been microprocessors, and this guy is just perpetuating that misconception.

One of the big drivers for digital displays was the early digital instrumentation of the 1950s. We started the decade (before I was born) with digital columnar waterfall displays: columns of 10 bulbs for each decade. These instruments show up in early SF movies about atomic weapons.

The first “mass market” digital instrumentation to appear were DVMs like the ones from NonLinear Systems and Cubic. The earliest models of these devices used stepper relays adapted from telephone switching systems. No electronics. All electromechanical. That’s where we got those cool incandescent bulb and Lucite displays. Nixies appeared in 1955, which is the only technical flaw I saw in “Oppenheimer,” which used a Nixie countdown clock for the Trinity test, 10 years before Nixies were invented.

The author of the video thinks that early calculators were microprocessor-based. LSI calculator chips predated microprocessors by four or more years and their popularity did a lot to drive the development of 7-segment displays including VFDs, LEDs, and Panaplex gas discharge displays. Digital clock chips from companies like Mostek similarly drove display development. One of the big reasons why Heathkit digital clocks are popular is because they used those beautiful Panaplex 7-segment displays.

He missed his chance to talk about the 7-segment displays used for the Apollo Guidance Computer’s DSKY user console, which used custom electroluminescent 7-segment readouts.

He made a big deal about how 7-segment drivers need only 8 segment drivers while unary decimal drivers need 10. Honestly, two pins ain’t much of a much. Minimally, you need a 16-pin DIP instead of a 14-pin DIP for a decimal decoder, but the 7447 BCD to 7-segment driver came in a 16-pin DIP, so it’s in the same package as a 74145 BCD to decimal decoder. In the video’s beginning, I think he shows the Russian copies of the 74145.

Although I agree with almost all of the Numitron downsides that the author pointed out, saying that the things weren’t actually polychromatic because they’re short of blue photons (given that they’re incandescent) feels gratuitously disingenuous to me. I’m reasonably certain that Numitrons were killed off once Fairchild, Monsanto, and HP got rolling on 7-segment LED displays which were more rugged, used less power, and were dimensionally more consistent.

I wish Steve wouldn’t hold back so much. Now we are left wondering what he really feels (LOL). I was still cogitating and ruminating on the aforementioned video when my friend Jay Dowling sent me a link to something called the Valve.Computer (yes, that’s how it’s written). 

This is an amazing DIY project involving a modern 8-bit processor architecture implemented using thermionic valves (vacuum tubes) from the 1950s.

In addition to the main page, which includes some great pictures and videos of this bodacious beauty working its magic, there is a very tasty technical page that details the construction of NOR gates and other functional elements using these tubes.

But wait, there’s more, because I just fell down the rabbit hole known as the art page. OMG! I want to build all of these!!!

I also have to say that I love the writing style on this site, where we find things like, “After about a minute the Valve.Computer has the pleasant homely aroma of 560 double valves, quietly burning off their dust,” and “When all the valves are glowing, I check the fire extinguisher is full, and run the code.”

Now, in addition to thoughts of building my own vacuum tube computer, I feel an urge to return to the art page to decide if I have the time and energy to create my own versions of any of these displays. How about you? What do you think about all of this?