Spark Gap Tubes, Trigger Tubes & Passives

This section is a catch-all for simple vacuum and gas-filled devices used in relay and passive applications.

 


Bomac JAN-CBNQ-724B
 

The 724B is a TR cell, a device used to protect the receiver portion of a microwave transceiver which shares the same antenna for both transmit and receive functions. A TR cell functions like a triggered gap tube, and blocks the receiver hardware by shorting the receiver input during transmitter operation. Transmitter pulses cause the spark gap to break down, shorting the receiver input. The 724B is filled with water vapor, which produces a blue glow when ionized by a high voltage field.

The 724B was used in several WWII-era 10GHz mobile radar systems, including the AN/APS-1, ASD (AN/APS-3) ASH (AN/APS-4) and AN/MPG-1.

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Bomac JAN-CBNQ-724B TR Cell Tube
Electronic Products 7616 / EP72M
 

The EP-72M/7616 is a small cylindrical Geiger tube capable of detecting alpha, beta, and gamma radiation. The front of this tube is sealed with a thin mica window, which allows weak alpha radiation to penetrate the tube and ionize the neon and halogen gas within. LND still manufactures a version of this tube, the LND-7616, which is a popular choice for electronic enthusiasts looking to upgrade the commonly available CDV-700 Geiger counter for increased sensitivity. The 7676 is ideal for this task, as it is small enough to fit inside the original probe that this meter was equipped with, though the builder would be required to cut a hole in the end of the probe if they intend to use the alpha particle detection feature of this tube.

LND-7616 Datasheet (PDF, 144kb)

Electronic Products 7616 / EP72M Geiger Tube
Central Electric CVS-1
 

The Central Electric CVS-1 is a high voltage vacuum switch constructed into a large T-shaped envelope. This tube has three contacts; a fixed contact imbedded in glass, and two movable contacts that pass through sheet metal plates. The plates are flexible, allowing the movable contacts to opened and closed by an external force without breaking the vacuum. The tube's getter is located in one leg of the tube, attached to the base of the fixed contact.

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Central Electric CVS-1 Vacuum Switch Tube
Sylvania 0A5
 

The 0A5 is a gas filled trigger tube designed as a high speed replacement for clunky mechanical relays. The 0A5 is a descendant of "Strobotron" neon filled flash tubes like the 1D21, but has an anode structure specifically designed for fast switching. In fact, one of the recommended uses of the 0A5 is as a trigger for gas filled flash tubes like the Strobotron. Sylvania departed from their normal print manufacturing techniques for this tube and put a lacquer coating over the logo and part number, similar to the coating used on some Russian tubes, to protect it from damage.

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Sylvania 0A5 Trigger Tube
GA4 (Unknown Mfr.)
 

The GA4 is a large spark gap tube of unknown specification. The two electrodes on either side of the envelope are designed to be removed, and are held in place by a pair of Allen screws. This tube illuminates purple when subjected to an electrostatic field, which suggests it is filled with either hydrogen or water vapor, depending on its original purpose.

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GA4 (Unknown Mfr.) Spark Gap Tube
Unidentifed TR Cell
 

We do not know much about this mysterious device or it's intended purpose, other than that it appears to be a TR cell or possibly a Geiger tube based on it's outward appearance. The tube is divided into two chambers and has only two electrodes, a pin electrode in the smaller chamber and a tubular one that sits to one side. The longer chamber is capped with an evacuation nipple and contains no other structures. The tube appears to be filled with neon and other unidentified gasses, and lights brightly under the influence of an ion source.

If you can identify this device, please contact us.

Unidentifed TR Cell
Sperti 473384-2
 

This device, which functions as a vacuum relay, consists of a spark gap bridged by a pivoting metal contact mounted on a glass bead. The entire mechanism is sealed in a complex T-shaped vacuum envelope. The underside of the tube is sealed with a rubbery material, allowing the contacts to be mechanically opened and closed by pressing the terminal exiting the bottom of the tube.

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Sperti 473384-2 Vacuum Relay Tube
Sylvania 6068A
 

The 6068A is a relatively undocumented TR cell with a complex internal construction. The cavity of this tube appears to be wholly separate from the actual waveguide interface, which is the large copper block in the center of the tube. The center of the copper block contains a tunable spark gap, which can be adjusted by turning a screw in the large steel cylinder at the base of the tube. Note that this tube has two separate sealing pips, and possibly contains separate cavities.

In outward physical appearance, this tube appears almost identical to the 1B24, a tunable TR switch tube with a rating of 8.5 to 9.6GHz. The 1B24 was developed in 1943 by Westinghouse

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Sylvania 6068A TR Cell Tube
Sylvania 5823
 

The 5823 is an argon-filled trigger tube in a small 7 pin envelope. This tube is triggered by a 70 volt signal, and can switch a load of up to 200 volts. The 5823 is a cold cathode device; unlike some gas filled switching tubes, no filament voltage is required. This tube produces a purple discharge when subjected to a high voltage field.

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Sylvania 5823 Trigger Tube
Sylvania BW382
 

We don't know much about this TR cell, but it is almost surely one of the smallest of such devices ever put into production. Little more than a glass window, the BW382 is quite small; dimensions are 24mm by 12mm and the device is a mere 1mm thick. The BW382 does not have any mounting holes, and is likely designed to be held in place by friction.

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Sylvania BW382 TR Cell Tube
G.L.A. 20750
 

The 20750 is a small spark gap tube in a cylindrical glass envelope. We can find no information on this device, but we suspect it was most likely used as an overvoltage protection system in some high power transmitter. The tube does not appear to be gas filled, and has no discharge when subjected to an RF field.

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G.L.A. 20750 Spark Gap Tube

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