Diodes, Triodes, Tetrodes & Pentodes


General Electric KR-9

The KR-9 is a powerful high voltage rectifier used in x-ray machines and similar devices. The tube is contained in a very unusual frosted glass envelope with a large bare metal dome and anode cap. The dome terminates in a threaded connector for secure connection of the anode wire. Some versions of this tube replace the bare metal dome with a black metal shield which extends down to the first rib on the glass envelope. The tube is quite large: length is 7" and the tube has a diameter of 3" at its widest point.


General Electric KR-9 Rectifier Tube
GM Delco 2DV4

The 2DV4 is a relatively common Nuvistor part number, similar to the even more common 6DV4 medium-mu triode, but equipped with a 2V heater filament. This example is rather unusual however, in that the manufacturer, General Motors, has chosen to apply a gold plating to the entire outside surface of its case, affording it a thin meniscus of protection from the harsh, McDonald's burger wrapper-laden environment of an average US motor vehicle.

The Nuvistor was developed by RCA as a response to what would ultimately be an overwhelming invasion of solid state electronics. They are packaged in a miniature metal envelope, and are comparable in size to early small signal transistors. Most Nuvistors were high performance triodes, though there are a few tetrode types.


GM Delco 2DV4 Gold Nuvistor Tube
Western Electric 316A

The 316A is a high power UHF triode in a large, spherical envelope. Commonly called a 'doorknob' or 'UFO' style envelope by collectors, this tube was manufactured by a number of vendors including Tung-Sol and General Electric; the example shown here was produced by Western Electric. The two cooling fins on the anode help to dissipate heat from the tightly packed components around the filament.


Western Electric 316A UHF Triode Tube
Raytheon CK6763

The CK6763, manufactured by Raytheon, is an instant start half-wave rectifier tube in an unusual 7 pin envelope. This tube has a unique form factor for a 7 pin device; the evacuation nipple has been moved to the side of the envelope to allow an 8th anode pin to be mounted to the top of the tube. This anode is shrouded in a glass extension to force the glow discharge to occur at the bottom of the pin. This tube was designed for use in high-vibration areas and all seven of the button base pins are connected to a common tubular cathode for increased ruggedness. In operation, a pair of CK6763 tubes would be ganged together to form a full-wave power supply rectifier circuit.

Raytheon CK6763 Datasheet (PDF)


Raytheon CK6763 Tube
RCA 6884

The RCA 6884 is a high power beam tetrode packaged in a robust metal and ceramic enclosure. The 6884 is rated at 80 watts of power at 400mhz, and the tube is dominated by the large aluminum heatsink permanently bonded to the tube's envelope. All external connections are coaxial with gold plated surfaces, the two center-most rings are the filament and cathode connections, with the anode and two grids taking the remaining rings. Understandably, the socket for this tube is quite complex, and includes a flanged ring to lock the tube in place as well as provision for forced air cooling on the large external heatsink. The 6884 was primarily used in airborne radar and communication systems due to it's small size and high power output. Though the example shown here is made by RCA, this tube was manufactured by a number of different companies.


RCA 6884 Beam Power Tube
Amperex 5867

The 5867 is a large power triode designed for use in amplifiers and industrial heating units. This tubes electrical limits are fairly robust; it is rated for an output power of 1200 watts at 4000 volts as a power amplifier. The eye-catching finned anode is constructed from graphite and is designed to hold and radiate the copious amount of heat this tube can produce when in operation. Additionally, this tube would normally be installed in a forced air chimney, which would help to carry excess heat away from the tube's envelope.


Amperex 5867 Power Triode Tube (5867A)
RCA 5876

The RCA 5876 is a UHF high-mu triode with a maximum frequency of 1000MHz and a maximum output of 5 watts. The most distinctive feature of the 5876 is it's unusual pencil triode form factor... the large disk in the center of the tube is the grid, and also serves as the grid's electrical connection. Two tiny pins on one end of the envelope provide connection to the tube's 6.3 volt heater filament. Suffice it to say, the socket for this tube is fairly complex. The 5876 was a relatively common tube produced by many manufacturers, and is readily available from most surplus suppliers.

RCA 5876 Pencil Triode
Telefunken RV12P2000 Pentode

The 'Wehrmacht' RV12P2000 pentode was one of the most prolific tubes used by Nazi Germany during World War 2, and saw use in nearly every type of electronic device employed at the time. The tube's unusual six pin base was designed to be mated to a special wraparound socket that would completely encircle the tube; unlike most tubes the RV12P2000 was designed to be inserted into its socket with the anode cap facing downward. The tube has a small threaded bushing in the center of its base, when installed a pull handle would be attached here to make it easier to remove the tube from its socket.

The RV12P2000 was such a popular and reliable tube that it saw considerable use in Germany even after the war ended. The example shown here was most likely manufactured in 1947, based on the print style and shape of its anode cap.


Telefunken RV12P2000 Pentode Tube
Raytheon 0Z4G

The 0Z4 is an argon filled full wave rectifier tube. Most 0Z4s have an opaque metal envelope, the example pictured here is the somewhat rarer glass envelope '0Z4G' variant. As can be seen in the photo, the glass version of this tube allows the argon glow discharge to be seen during operation. This tube is designed to fit in a standard octal socket, though only five of the eight pins have been populated.


Raytheon 0Z4G Rectifier Tube
RCA 7587

The 7587 is an oddity, a Nuvistor with an anode cap. The 7587 is a sharp cutoff tetrode, which was released in 1961. Inside this tube's tiny shell is a pair of coaxial grids surrounding a heater and tubular cathode. The entire top shell acts as the plate, with a ceramic band to isolate it from the typically grounded lower shell. This example is still contained in its original packaging, showing how Nuvistors and their sockets were boxed for the commercial market.


RCA 7587 Nuvistor Tube
Eimac 2-01C

The 2-01C is a high frequency rectifier tube rated at 2.8 Ghz. This tube makes use of a fragile metal-to-glass seal which also contains the tube's pinched-off evacuation nipple. 2-01C tubes were commonly used in the AC probes for Hewlett Packard vacuum tube voltmeters, but were replaced in newer models with the EA53 tube, a more rugged tube with a spring-loaded contact.


Eimac 2-01C Rectifier Tube
RCA 8072

The RCA 8072 is a compact VHF linear amplifier tube, packaged in a cermet-style ceramic bonded metal envelope. The 8072 has a maximum power rating of 110 watts at 50MHz, with reduced maximum wattage ratings at higher frequencies. The ring-shaped terminal at the lower end of the tube provides a alternate connection to the second grid; when operated at high frequencies this ring terminal must be used to connect to the second grid instead of the pin on the base of the tube. The 8072 can become quite hot when in use, and the anode connection is designed such that it can be connected to a heatsink if needed to help cool the tube..


RCA 8072 Power Amplifier Tube
General Electric Tungar Bulb (Unknown P/N)

A Tungar bulb is a simple type of rectifier tube used to generate DC current in car battery chargers and other similar devices. The tube has a lightbulb-style base which connects to a directly heated cathode; the carbon pellet anode connection protrudes from a clay bead at the top of the tube. The tube envelope is filled with a mixture of low pressure argon gas, which results in a purple discharge when the tube is in operation. The heavy silvering and side nipple make the tube rather attractive, despite its primitive construction. The part number for this device is unknown, but it was manufactured by General Electric.

Incidentally, trade name "Tungar Bulb" is a portmanteau of the words tungsten and argon, the two primary elements used in the bulb's construction.


General Electric Tungar Bulb (Unknown P/N)
Western Electric 416B

The Western Electric 416B is a gold plated planar triode designed for high frequency transmitters. The 416B has an unusual package with a ring shaped threaded gold contact, which anchors the tube in place when installed. The evacuation nipple is made of metal and located in the bottom of the tube.


Western Electric 416B Planar Triode Tube
RCA 446A

This strange looking tube is a 446A lighthouse triode, called such due to it's unusually shaped envelope. This high-frequency tube is designed to be mounted in an external cavity, which would separate the input and output sides of the device. The two glass chambers on the top of the 446A are separated by a thin screen which acts as the grid. The 446A was originally intended for use as an amplifier in radar receivers.


RCA 446A Lighthouse Triode Tube

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