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| Gas Discharge Displays |
Gas discharge displays are low pressure neon lamps with multiple, shaped or shape-shaded cathodes. Tubes in this family include Nixie, Pixie and Panaplex
displays, most of Burroughs origin. Nixie tubes were driven
by a range of decade counter technologies, including hard valve and thyratron decades, dekatrons, beam switching tubes, discrete transistor counters
and specialized TTL devices. The earliest gas discharge displays were patented in 1934 by an inventor named Hans Paul Boswau, who envisioned all sorts of useful applications for such numeric display tubes. Boswau's cumbersome device consisted of shaped wire cathodes sandwiched between glass or mica disks in a large end-view envelope, and never entered commercial production. In 1954, National Union began to market their own numeric gas discharge tube, which dispensed with the glass plates of Boswau's device and replaced them with stiff wire supports. It was not until Burroughs added an anode mesh and a new gas mixture that numeric gas discharge displays became a practical device. Electronics lore has it that the name 'Nixie' originated when a Burroughs draftsman labeled drawings of the tube NIX1, shorthand for Numerical Indicator Experimental 1.
| Burroughs 4021L | |
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This Nixie tube ranks as one of the smallest circular envelope displays ever made; the digits are a mere 8 mm high. This model of tube was made in both standard pin and flying lead variants; the flying lead model is shown. The 4021L has digits 0-9, with no decimal point. One of our samples is still mounted in its Lucite store display. It is hard to imagine a time when you could walk into a store and see an array of Nixie tubes on display like a row of blenders at Wal-Mart. |
| Burroughs B4998 | |
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The Burroughs B4998 is the smallest Nixie tube ever mass produced, it's tiny elliptical envelope is only 15mm high and 10mm wide. The B4998 contains the same 8mm digits as the 4021L tube shown above, but the elliptical envelope reduces the overall size of the tube and allows for tighter side-by-side installation of multiple digit displays. B4998 nixie tubes are highly coveted among modern hobbyists for use in construction of 'Nixie watches' and other tiny Nixie displays. Ironically, the integrated driver modules provided by Burroughs for use with the B4998 are much bulkier than those manufactured for it's larger tubes. |
| Burroughs B-5560 | |
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The B-5560 is an oddity, an upside-down mount tube. Unlike most side view nixie tubes, which have leads exiting the bottom of the envelope, the B-5560's leads exit at the top of the envelope. Digit height is 13mm and the height of the envelope is 30mm. The B-5560 is primarily used in Hewlett Packard test equipment. Note: Despite the color in the photo, the discharge from this tube is orange like other nixie tubes. The bright pink glow in the photo is an artifact of the high amount of UV generated from the glow dischage. |
| Burroughs B7971 | |
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The large and unwieldy Burroughs 7971 is the iconic example of an alphanumeric Nixie tube. The display contains a series of wire cathodes arranged into an array of 15 segments and an underscore character, unlike modern 17-segment LED displays, the top and bottom vanes have been ganged together on a single control line. Despite their staggeringly high price on the resale market, 7971's are a relatively common tube, the tube's large size and high functionality have made it the display choice for nixie projects and demand has increased accordingly. In the time before the Nixie clock craze, 7971's could regularly be bought from electronics suppliers for less than a dollar per tube. Despite electronics lore to the contrary, 7971 nixie tubes were never used in the marquee at the New York Stock Exchange. The primary (possibly only) commercial use for the 7971 is in Ultronic Letrascan stock tickers, which collectively generated sales for hundreds of thousands of tubes. The Lectrascan display contained a staggering 48 7971 display tubes, along with a veritable hardware store of transistors and other discrete driver circuitry. |
| Burroughs 8422 | |
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Also known as the B-5991, the 8422 is a common Burroughs top-viewing Nixie, which features a moderate digit height in a compact envelope. The 8422 displays digits 0-9, with no decimal point. |
| Burroughs HB-105 | |
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The problem with Nixie tubes, both in the 1960s and now, is that they are simply far too expensive. Pixie tubes are a curious technological dead-end, an attempt by Burroughs to make a cheaper, more affordable gas discharge display. Instead of having a series of shaped cathodes for each digit, a Pixie tube has a single shaped anode with number shaped holes over each of the pins in the stamped glass base. Stub cathodes are attached to the top of each pin, which glow through the holes in the anode during operation to indicate a numeric value. Pixie tubes cost only about a quarter as much to manufacture as a Nixie tube of similar size. The low cost did not win over users however, a Pixie tube produces a remarkably tiny and unreadable display, and most early Nixie tubes were used in equipment costing many multiples of thousands of dollars where the expense of the display could be justified. Nobody knows what the first Pixie tube part number is, but given the HB105's Haydu part number and ridiculous oversized envelope, it is definitely an early example. Ironically, Pixie tubes are now quite a bit more expensive than the Nixie tubes they were originally designed to undercut; they are quite popular among electronics hobbyists for making clocks and other novelty items. Burroughs originally marketed the tube's ability to be controlled by a five volt differential in an attempt to make the tubes seem more 'transistor friendly', but modern hobbyists typically drive them with standard Nixie circuits instead. |
| Burroughs HB-106 | |
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The HB-106, as indicated by its Haydu part number, is an early model of Burroughs top view nixie tube. Haydu parts which were manufactured under Burroughs begin with the "HB" prefix, Burroughs eventually stopped using the Haydu brand name and later part numbers were prefixed with a "B". This tube has a silicone surround that is integral to the part, which was included to increase readability in high brightness conditions. The part number is printed on a plastic wrapper affixed to the surround. Unfortunately, as this example shows, the plastic wrapper is just as prone to disintegration as the water soluble paint used on most other models of tubes. |
| National Union GI-10 'Inditron' | |
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The GI-10 'Inditron' is an historical curiosity, a Nixie-style numerical indicator tube which was developed in parallel to the more successful Burroughs Nixie, and may actually predate the Burroughs Nixie by as much as a year. Beginning in 1954, National Union produced a small number of neon-filled indicator tubes which used bent wire cathodes to indicate a numeric value. The tubes had very short operational lifespans and were difficult to drive with the contemporaneous technology, which prevented widespread use and ultimately doomed the tube to failure in the market. |
| Sperry SP-15x & SP-35x Series | |
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Devices included in this entry: |
| Sperry SP-33x Series | |
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Devices included in this entry: |
| Beckman SP-450 Panaplex Display | |
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This late model panaplex display shows many of the manufacturing changes that Beckman and others made to their designs as panaplex manufacturing techniques matured. Instead of using the black glass "bathtub" style envelope seen on earlier displays, the SP-450 uses a glass sandwich which is almost identical to the package seen on early LCD displays. All of the leads exit along the edge of the envelope instead of out of the back, and no provision is provided to socket the display for easy replacement. The display itself is 6 digit 7 segment with decimal points. There are also twelve triangular indicators on the sides of the display, normally the small triangle shaped cathodes inside of such a display are intended to be used as "keepalive" electrodes for faster striking, but the location of these cathodes in the package suggests that they may be intended for actual information display. The board shown contains two SP-450 displays and no other driver hardware. |
| NEO5000 Gas Discharge Display (Unknown Mfr.) | |
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The NEO-5000 (also sometimes called the NEO5000), is a neon-filled seven segment display in a flat, 'Panaplex'-style glass planar envelope. This display is quite large; digit height is 50mm and the tube envelope is 84mm tall. The NEO-5000 uses fairly modern construction techniques; the envelope is made of a glass plate sandwich with fritted seals and epoxied leads. Lifespan is rated at about 35,000 hours, which, while much better than various 'short life' early nixie tubes, is shorter than many other gas discharge displays. Special care should be taken with this display's exposed top nipple, which is quite fragile and easily broken. |
| Melz ITM2M | |
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The ITM2M (also sometimes called the ITM2-M) is a strange device, a Soviet-manufactured indirect gas discharge display. Like a Nixie, the ITM2M is filled with low pressure ionizing gas, but all similarities to more common displays end there. ITM2M tubes contain an array of 16 tiny thyratrons, each painted with one of four colored phosphors. Activating one of the thyratrons causes the gas within to ionize, causing the phosphor to illuminate. Though these tubes require a power supply of approximately 250 volts to activate, the switching action of the thyratrons allows individual pixels to be activated with a relatively low voltage signal. The ITM2M is packaged in a tiny cubical envelope, allowing for the construction of large tiled displays. |
| Pantek NCR08501 | |
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It is hard to think of a time when VFDs would have commanded such a premium over neon-filled Panaplex displays that a manufacturer would actually try to paint a Panaplex display to make it look more like a VFD, yet the NCR08501 is just such a boondoggle device. Every one of the NCR08501's eight digits has been painted with a white stencil, to trick the user into thinking they are looking at a VFD. Make no mistake though, the NCR08501 is a Panaplex device, it is filled with neon, it lacks filaments and control grids, and the digits light up with an orange gas discharge. The display has 84 pins and is quite large; much of the display's surface area is taken up by the illuminated arrows that ring the numeric portion of the display. Though the display panels are welded together with a fritted glass barrier that should be nearly indestructible, the evacuation nipple appears to soft-sealed with nothing more than a blob of epoxy. This example still has it's original fill gas, but soft-seal epoxy is notoriously failure prone; it is unknown how much extended use such a display could endure. |
| ETL GR10A | |
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Though it resembles a dekatron, the GR10A is actually a register tube - basically a Nixie or Pixie tube shaped like a dekatron. Register tubes were designed to provide a consistent display when dekatrons were used in conjuntion with beam switching tubes or hard valve decades in the same counter. The visible glow extinguishes above ~50 kHz, and reappears at lower speeds. |
| Sovtek IN-1 | |
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The Sovtek IN-1 is a large Soviet nixie tube with an end-view envelope and phenolic base. The IN-1, unlike most other gas discharge displays, does not contain any mercury in it's fill gas, which substantially shortens the tube's lifespan. Under normal conditions, the number cathodes in an IN-1 will completely dissolve after only a few thousand hours of operation. The IN-1 is a larger nixie; digit height is 12mm and the tube has a diameter of 30mm and a height of 60mm. The tube's unusual 11 pin phenolic base is practically impossible to find a socket for, though the truely desperate can repurpose Molex pins from an ATX power supply to act as a socket stand-in. The combination of the IN-1's short operational lifespan, obscure base, and abysmally poor, "prop from The Dark Crystal"-style construction make this tube almost universally loathed by electronics hobbyists. |
| Sovtek IN-2 | |
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The IN-2 is the Soviet equivalent of tiny American tubes like the Burroughs 4021. The digit height on the IN-2 is 10mm and the envelope diameter is 17mm, which makes it slightly larger than a 4021. The IN-2 has a high domed front and a side nipple that exits the tube at a 45 degree angle to the digit, for multiple tube displays. The print on the side of the tube is covered with a resinous coating, which protects the print from being wiped off by the person installing the tube. The main drawback of the tube is its tiny base, the socket for the tube is rather hard to find, and the pin spacing is very narrow, making attachment of leads difficult. |
| Sovtek IN-17 | |
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The IN-17 is the smallest nixie tube that Sovtek ever manufactured. Digit height is 9mm and the envelope is only 10mm wide at its narrowest point. The IN-17 has a flying lead base with a colorful plastic spacer to hold the tube away from the board it is being attached to. The spacers on the IN-17 come in a wide array of different colors. |
| RFT Z560M | |
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The Z560M is a top-view Nixie display in a compactron style envelope with a 13 pin base. Made by RFT, the Z560M is a shorter, stubbier analog to the Burroughs B5092, which is shown below. The upper surface of the Z560M is coated with a layer of translucent red paint, which increases the contrast of the displayed numbers. Digit height on this Z560M is 15mm, the tube has a diameter of 30mm and a height of 24mm. |
| Rodan MG-17F | |
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An unusual tiny 7-segment nixie display. This tube has upper and lower decimal points, allowing it to be mounted normally or with the leads exiting the top of the envelope. |
| Burroughs B-5092 | |
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A medium sized round top view nixie with standard numerals and a 13-pin base. Digit height is 16mm and the envelope is 20mm in diameter. |
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