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Vacuum Fluorescent Displays

Vacuum fluorescent display tubes share more in common with a cathode ray tube than they do with the Nixie tubes they tend to mimic. A VFD tube has a low voltage filament which is energized in a vacuum, causing electrons to 'boil' off. Metal plates covered with a phosphor coating are charged to between 25 and 50 volts, causing electrons leaving the filament to strike the plates and illuminate the phosphor. Later models of VFD also have a control grid, a metal screen that is placed between the digit and the filament. The control grid acts as a valve, allowing the digit to be turned on or off without the need to power down and re-heat the filament.

General Electric Y1938
 General Electric Y1938

Devices included in this entry:

General Electric Y1938 (nine pin base)

General Electric Y4102 (overflow indicator, nine pin base)
General Electric blue-dipped Y1938 (nine pin base; pictured in thumbnail)
General Electric prototype Y1938 (nine pin base)

An early VFD tube, the General Electric Y1938 is an attractive display in a classic nine pin envelope. This device is a bit higher quality piece of construction than the Tung-Sol Digivac VFDs shown elsewhere on this page--Y1938 tubes have more evenly lit digits and higher build quality overall. Some 1938s have holes where a decimal point would have appeared, while others do not. Some units also have a thick blue coating over the glass, to improve the color of the digits. It is unknown whether this blue coating was applied by GE or by a secondary manufacturer. General Electric also manufactured a companion overflow indicator for the Y1938; the Y4102. This overflow indicator tube has separate tiles to display a plus or minus symbol, in addition to the '1' segments and a decimal point. Prototypes of the Y1938 have a radically different internal construction, incorporating a printed VFD material on a ceramic substrate instead of the separate tiles used in production VFDs. It is unknown why this apparently superior manufacturing process was abandoned in production devices.

Of important note to the modern day hobbyist is that this tube lacks a control grid, a refinement not added to VFDs until after this tube was manufactured. With no control grid, this display can not be multiplexed

General Electric Y1938 Datasheet (PDF, 136kb)

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General Electric Y4075
 General Electric Y4075

The rather hard to find Y-4075 display tube is the smaller cousin to the General Electric Y-1938 display shown above. Like the Y-1938, this tube is constructed using a series of phosphor coated tiles that are arranged in a seven segment pattern with decimal point. This is a very early VFD part number, and like other early tubes it lacks a control grid, making it nearly impossible to multiplex.

The example shown here was actually repackaged in an Archer blister pack for sale at a Radio Shack retail store. The mind boggles at the thought of a time when Radio Shack sold things other than batteries and bottomless piles of tawdry consumer goods.

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Futaba 9CT06
 Futaba 9CT06

The Futaba 9CT06 is a tiny 9 digit VFD, designed for use in handheld calculators. This display has a long tubular envelope with a central evacuation nipple and conventional 7-segment digits with decimal points. The 9CT06, like most VFD's, has a control grid installed above each digit to allow for multiplexed displays.

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Iseden Itron DG10A
 

This flying lead display tube has color coded plastic sleeves on its leads, which makes it easier to wire than most VFD tubes. The tube is smaller than most, the envelope height is only 26mm and digit height is 9mm.

An interesting sidenote about this tube is that they are very well packaged compared to most other tubes. Instead of being rudely stuffed into a cardboard box, the samples we have were carefully wrapped in tissue paper and then individually sealed in rigid plastic containers.

Iseden DG12C
 

The DG12C is an eight segment display, capable of generating both numbers and signs. The display has a right decimal point and a left colon indicator. Digit height is 11mm and the envelope is 42mm high. This tube has a somewhat more rounded top than most newer vacuum fluorescent tubes, which some find more visually pleasing.

Iseden DG19E
 Iseden DG19E

The DG19E is a large, attractive VFD with a curved top and shaped flying leads. Digit height is 15mm and the envelope is 41mm long. The display has a control grid and an eighth segment, allowing the tube to display a plus sign in addition to normal seven segment numbers.

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Tung-Sol DT-1704C 'Digivac'
 Tung-Sol DT-1704C 'Digivac'

An early VFD tube in a narrow 9 pin envelope, seven segments with no decimal point. Like other early VFD tubes, this device predates the inclusion of a control grid and therefore can not be multiplexed. This model of tube seems to be very failure prone; bent heater filaments and uneven or partially unlit segments are common. The pinouts of this tube are identical to the General Electric Y-1938 display shown above.

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Tung-Sol DT-1741C 'Digivac'
 

A "symbol" variant of the Digivac tube listed above, with two elements, one labeled 'TAX' and the other labeled 'CRD'. The tube has the same narrow nine-pin envelope as the DT-1704C, though only five of the pins are connected. This tube was originally salvage from the old NCR factory, and was intended for use in a NCR cash register. Though practically useless to the modern enthusiast, VFDs such as this which display something other than a segmented display are exceedingly rare.

NEC LD8012
 NEC LD8012

The LD8012 is a VFD tube designed for upside down mounting. The tube has twelve flying leads which exit the upper surface of the tube, the nipple and getter are on the underside. Digit height is 20mm and the envelope is 37mm high. The picture to the left was taken with a digit voltage of 25 volts and a filament voltage of 1 volt.

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NEC LD8113
 NEC LD8113

The LD8113 is a large, attractive VFD tube with a flat top and flying leads. The tube's unusual segment arrangement allows a single tube to generate both numbers and signs, as well as some alphabetical characters. Though the tube appears to have 10 segments, the four horizontal and vertical segments in the center of the display are ganged together to form an 8-segment tube. Digit height is 14mm and envelope height is 43mm excluding the tube's nipple.

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Russian IDL1-Derivative Indicator
 Russian IDL1-Derivative Indicator

Many unusual display tubes were manufactured by the Soviets during the Cold War, but this strange device shows that even the humble pilot light is not beyond replacement with a complex electron tube. This display contains a red phosphor target, control grid, filaments, and all the other elements of a typical VFD display, but instead of displaying numbers or symbols the tube is dominated by a single square target that fills nearly the entire face of the envelope. We have no idea why such a device would be created, but since the display contains a control grid, it is possible it was intended for high-speed indication applications where the latency of an incandescent light bulb would be unacceptable.

The exact manufacturer of this display is a bit of a mystery. The device appears mechanically identical to a Russian-made ILD1 single pixel indicator, but the ILD1 uses a green phosphor, not the red seen here. Exhaustive research of all available Russian databooks has turned up no known red phosphor single pixel display in this package, which suggests that this may be a special order device or some sort of prototype.

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Soviet IV-29 VFD Tube
 Soviet IV-29 VFD Tube

The IV-29 is an uncommon Russian-made single dot indicator, built around VFD hot cathode technology. Much like the neon filled IN-28, the IV-29 is designed to be used as a single pixel in large segmented and bitmapped displays. This tube has a diameter of 29mmm and is quite large for a pixel indicator; the IN-28 and IV-29 actually use identical diameter glass envelopes in their construction, allowing the two tubes to be intermixed to make multicolor displays. The tube's flying lead base is designed to be directly soldered into the target device; the mind recoils at the thought of replacing burned out bulbs in a large matrix display constructed of these.

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Soviet IEL-0-VI Electroluminescent Display
 Soviet IEL-0-VI Electroluminescent Display

The IEL-0-VI represents a not-often seen class of display that was used almost exclusively within the former Soviet Union; a segmented electroluminescent display. Segmented EL displays use phosphor, but are fundamentally different from VFDs in that they are not vacuum tubes and do not have a hot cathode filament. Instead, an organic resin with a crystalline phosphor suspension is sandwiched between a conductive bottom layer and a tin oxide glass window to form a capacitor, similar to the way in which modern EL wire works. When rapidly charged and discharged by a high voltage source, the phosphor emits light which can be seen through the glass front of the display. The IEL-0-VI requires an AC voltage of approximately 200 volts at 400hz to function properly; approximately 8 times the voltage required to light a similar size VFD. The strange looking high-efficiency segment pattern serves a special purpose; it can generate nearly every Cyrillic and Roman character (except the letter T) using only eight segments.

The IEL-0-VI and other displays of its family are ruggedly constructed out of a glassivated material, which can withstand extreme punishment that would destroy a conventional VFD. Electronics lore has that these displays were originally intended for use in the cockpits of Soviet tanks.

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Russian Reflector ILC1 1/7
 Russian Reflector ILC1 1/7

The ILC1 1/7 is a massive Russian-made seven segment display that might well be one of the largest single digit VFD displays ever constructed. The ILC1 1/7 is built using a nearly modern VFD envelope design; two plates of glass have been stretched and molded to form a hollow sandwich that contains the display components. The evacuation nipple is located on the rear of the display and can be easily damaged, special care must be taken to prevent the nipple from being crushed or broken when installing the display. THe ILC1 1/7, like nearly every modern VFD, has a control grid which allows multiple displays to be multiplexed for easier control by a microcontroller. The display's clipped corner seven-segment pattern and perfectly clear glass back make it an attractive, if expensive choice for projects; unlike most Russian surplus tubes the ILC1 1/7 can command a painful price premium due to its size and the difficulty of obtaining one outside of the Russian Federation. The example shown here was manufactured by the Reflector factory in 1992.

Special thanks to Terry Kennedy for donating this part.

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Russian UDT-3
 Russian UDT-3

The UDT-3 is a very large Russian bitmapped VFD display in a conventional flat envelope. Unlike most matrix displays that are manufactured with a 5x7 or 8x8 dot pattern, the UDT-3 contains a 9x7 array of phosphor coated squares, with control grids affixed over each row. This tube has a distinctly modern appearance and construction and is enclosed in a fritted glass sandwich envelope like any other readily available VFD. The UDT-3 is post-Soviet, and the example shown here has a date code of August 2008. It is likely, given it's time of manufacture, that the UDT-3 is intended specifically for the export market. Builders should take note of the exposed rear nipple during construction, as it is easily broken. Although this display has no factory mark, we strongly suspect it was manufactured by the Volga Institute.

It should be noted that a large portion of these displays appear to have an intentional mechanical defect whereby a metal bar is installed across all of the horizontal grid elements, shorting them together. This makes it impossible to use the display in a bitmapped fashion, only entire rows of dots can be controlled. The collector is advised to exercise extreme caution when purchasing one of these displays, lest they inadvertently buy a device which can not be used to display characters.

Special thanks to Terry Kennedy for donating this part.

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Soviet Reflector ILV2-5/7M2
 Soviet Reflector ILV2-5/7M2

The ILV2-5/7M2 is an uncommon Soviet 5x7 VFD matrix with a special trick, the ability to display characters in full RGB. This colorful device contains 105 pixels arranged in five rows of 21, and has a separate red, green and blue pixel for each position. The tube is packaged in a standard 'bubble' style flat envelope common to many Soviet displays and has a side nipple and separate glass stiffener bars that have been cemented into place around the edges of the display. Despite this readout's RGB status, full color image display is almost impossible due to the large asymmetrical gaps surrounding each pixel; this display excels mainly when displaying static infographics of very low color depth.

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Soviet Reflector ILM2-9MV 'Jumbotron' VFD Display
 Soviet Reflector ILM2-9MV 'Jumbotron' VFD Display

The ILM2-9MV is a large Russian three color VFD intended for use in the construction of 'jumbotron' style full color displays. This tube consists of three pixels, each constructed out of three colored bars. For either cost or availability reasons, a pale green phosphor is used for both the blue and green color bands; a colored lacquer is applied to the outside of the tube over the blue and green sections to create a three color device. The tube's rear mounted nipple has been offset so that it does not coincide with one of the display pixels. The VFD-based technology in this tube is dimmer than that in Futaba's competing CRT-based products like the TL-3508XA, but it is much easier to drive with solid state technology. The ILM2-9MV is a recent tube by Russian standards, these examples were made by Reflector in the mid-1990's for the export market.

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Russian Reflector P789
 Russian Reflector P789

The P789 is a nearly modern example of a Russian made 'jumbotron' style RGB display. Much like the ILM2-9MV shown above, the P789 is designed to be tiled into large arrays for the display of full RGB text or images. Unlike the ILM2-9MV, this tube has real blue phosphor for the blue-generating elements, which substantially improves the tube's usability. Strangely, the tube designers have placed the evacuation nipple directly in the center of the front of the tube instead of on the rear of the envelope, possibly to facilitate direct PCB mounting.

The P789 appears to be a relatively new tube manufactured for the Russian export market; the example shown here has a date code of 1994 and was manufactured at the Reflector factory.

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Soviet IV-4
 Soviet IV-4

The IV-4, a Soviet tube, is one of only a handful of single digit alphanumeric VFD tubes available. This large VFD display tube has a 17 segment display with left and right commas, for a total of 19 controllable display elements. This tube has a proper control grid for multiplexing, unlike some earlier single digit VFD's such as the Y-1938, shown above. The tube has a 22 pin flying lead base and can be directly soldered into a PCB without need for a special socket.

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Soviet Orzep IV-18
 Soviet Orzep IV-18

The IV-18 is a Russian multi-digit tube, which contains eight separate seven segment displays in a single envelope. Each digit has a decimal point, as well as its own separate control grid for multiplexing. The tube also has a separate overflow indicator digit that is half the width of the numerical digits. It should be noted that while it is common to blindly refer to all Soviet tubes as being manufactured by 'Sovtek', the example shown here was actually manufactured by Orzep.

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Soviet Orzep IV-21
 Soviet Orzep IV-21

The Soviet-made IV-21 display is a size-reduced sibling to the IV-18, designed for use in pocket calculators. The IV-21 is an eight digit, seven segment display with sign and overflow indicators.

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Soviet IV-22
 Soviet IV-22

The IV-22 is a Soviet single digit end-view VFD display tube, one of only a handful of end-view VFD devices manufactured. The tube's oval envelope is suitable for horizontal and vertical stacking and is very similar to the common 8422 nixie tube in dimensions, in fact an IV-22 can be shoehorned into an 8422 socket in times of desperation. The tube's large 18mm display includes a control grid for multiplexing applications.

The IV-22 is a fairly common tube and a good choice for a project, both the tubes and sockets are readily available from eBay and myriad smaller online resellers.

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