The Numitron: An obvious idea that wasn't very bright

SOME ADDITIONAL CONTEXT: I goofed here by not making clear that these wouldn't be naked in an actual product. They'd be placed behind a transparent panel, usually tinted which would reduce the impact of some of their worst flaws (however, I've seen some contemporary products which used these tubes and they're... better but still not great). Really, my issue isn't with the concept - it lived on much longer than the Numitron! My issue is with RCA's version of it: though pioneering, it wasn't very polished. (original pinned comment): Did you notice in some of the B-roll shots that they actually look more readable when they're slightly out-of-focus? That's the real downside of using segments thinner than a hair!

eBay sellers are going to be wondering why there's a run on Numitron tubes for the next 24 hours.

“Ignore all the continuity errors. It’s a running clock” Yeah not to mention the Krakatoa’s worth of lava lamps behind you

"Janky"...if I needed a "digital" clock in my aspirational Fallout-themed basement, I'd be happy with those.

"Numitron, take out Bumble Bee while I fight Prime" ~ Megatron 1972

Numitrons were designed to be used with a filter in front of them. this solves the issues you talked about. they were very popular in avionics displays because they can handle extreme temperatures and vibration, unlike the other technologies (including early LED displays, which were unreliable). typically they're driven at a constant current (rather than a constant voltage) and, while turned off, fed a small current which keeps the filament warm without illuminating it. this makes the filaments last a very long time. The displays you remember from '80s gas pumps were Panaplex displays -- basically a flat 7-segment neon-filled display designed for multiplexing. they also show up in a lot of pinball machines from the era. they required high voltage, just like Nixie tubes. although they can't handle a ton of vibration, they work well in extreme temperatures (think North Dakota in the winter) unlike LCDs which simply freeze and stop working. modern gas pumps have heaters to keep their LCD displays warm.

I like how you spent the entire video trying to convince us how bad the Numitron was, but only managed to make us fall in love with it

I just loved the massive displays in Airports in the 70s and 80s which had flip over flaps for letters and numbers, and took bloody ages to roll over an entire line when it changed and made a racket doing it. The electronics that drove them must have been amazing. Dot matrix designs replaced them, now small screens all over the place does their job.

My mom worked the graveyard shift, welding titanium wire into grids, for the innards of huge radio transmission tubes, in 1941. She did that for a year. Tubes were used on ship-to-shore radio among other things. That's not directly relevant to your video, but I'm proud of her just the same.

Numitron backing is grey because RCA used what they had in spades, the sheet steel with aluminium coat that was used to make anodes and internal structures for thermionic tubes, and this was proven to survive the glass sealing and gettering operations. Thus they used the standard tools they had in the tube plant, the flat anode sheet, slightly formed to be a stiff backing, and punched out the holes needed to hold the filaments. Then used the technology they had to make glass beads with wire in them, and sealed those into the holes, making the filament supports, and then simply used a flat section of that steel wire that was bent over to hold a length of thoriated filament wire, also a common item in the tube shop. Length and diameter calculated for the brightness needed at the applied voltage, and then simply placed in location, the ends folded over, then spot welded together to trap the tungsten wire under slight tension. Then at the rear spot welds to a lead frame attached to a standard off the shelf 9 pin glass base, and you have the complete unit. Glass top attached, and then evacuated with the standard roughing pump, and as a bonus because of the low voltage, and no need to maintain an ultra low vacuum, the roughing pump and the heat sealing of the tube is all that is needed to operate, no need for a getter to be installed, and no need to flash it, just a RF heating during sealing to get a high vacuum, then seal. Incidentally there were small versions made, the same size as your common 7 segment LED displays, and they were very popular, as they ran off 5V, and interfaced with logic. They worked best using CD4049/50 CMOS level shifting buffers, as those would source or sink 50mA no problem. Using a buffer/inverter per lamp, and a BCD decoder or counter per digit allowed those displays to be bright, and as bonus you could also use the blanking input on the drivers to use PWM to dim them. Project to replace those displays with LED ones worked, just that it really did not drop display current use, it was still 5A of current at 5V, though it was good in that at least you had a display that now was available, using a tiny HP 7 segment red display. Do one conversion and you had 16 numitron displays to use to fix others, so we only converted 3 boards to the LED version. Biggest problem was the resistor value selected was too low, so the LED displays were running way too bright, so had to be dimmed. Rather than destroying the cordwood board made to fit them, I simply used 2 6A silicon diodes in the common line, to drop the voltage seen by the LED displays down from 5V to 3V8, which made them dim to exactly match the old displays. Those 2 diodes were hard to fit in the limited space left on the display board. Users liked the new crisp displays, the bright version got complaints that it was so bright it was unreadable at night with dark adapted sight, and it lit up the entire cockpit. Display dimming had to match the other display, and that board used unijunction transistors, and had a disconcerting habit of the power transistor unsoldering itself from the wire leads, it ran so hot. Base lead unsolders itself, transistor is still conducting, runs hotter and lamp blows. Select spare lamp and it also blows, unless enough time for transistor to cool below 200C junction temperature. Would have been nice to have had some of the more modern mosfets that can handle 50A, but not at the age of that design.

"Now, I'm about to be rather unkind to this piece of alleged technology," he said after basically calling it a piece of shit

It might not scream quality, but it screams cool retro in a Brazil film style

20:05 Thanks for the shout-out to Dr. George Heilmeier. He was a University of Pennsylvania and Philadelpha legend whom I actually had the honor to meet and serve with on a board at Penn. Rest in Peace, George.

Displays like this predated microprocessors by several years - they were typically driven by discrete logic or even mechanical switches. By the time microprocessors were a significant thing, LED displays were available.

Numitron to me looks pretty dope. Elegant thin numbers, the amber glow, the smooth transitions between on and off state of each line. Everything - almost perfect design.

As a retired Analog Design Engineer in the 70's, I enjoyed the history of numeric displays. I still have plenty of them in my junk boxes.

The Spaceship Earth reference at 2:01 didn't go unnoticed! Masterful work, as usual, that made my day. 😁

There's something beautiful about how old technology worked. The combination of the limitations of the available electronics and engineering of the time resulted in some unbelievably wild ideas making it into every day products.

My wife and I were electronic engineers, and as a learning project we constructed a TTL 24 hour clock with this display design. We thought it was sharp, and a friend fell asleep on our bed one night watching the clock display, he claimed he was watching it!

Alec, I am just a middle age hard working hillbilly from the mountains of East Tennessee, but I want you to know that I appreciate you. We are very different people, but probably have tons in common. Thank you.