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The CV1128 thyratron specification was based on the commercial GT1C and had previously been known by other service codes such as the NGT2 and the VGT128 this example shows that the CV spec was equivalent to the GT1C.

This thyratron is from the 1930s and was used in timebases for Radar and television. At a defined grid voltage the valve, will rapidly switch to full conduction. The valve is turned off by reducing the anode voltage. Most thyratrons are gas filled and can be considered as triggered gas discharges. The precision of construction gives the defined and reproducible operating characteristics. This valve not only has a high peak current but is designed for operation at up to 8,000 pulses per second.

The first computer, Colossus, used these thyratrons as pulse generators. The operating speed of Colossus was 5,000 cycles per second.

The GT1C Type is also on the envelope.

The heater on the left and the insulated anode lead on the right.

The top shoes the layout with the cathode, copper grid supports and the anode at the other side. The mica fingers fit tightly into the shoulder of the envelope to form a rigid structure.

This exhibit is unused and the shaping of the pins is clearly seen.

The classic envelope is 45 mm in diameter and, excluding the B5 base pins, is 103 mm tall.

References: Data-sheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type CV1128 was first introduced in 1937. See also 1937 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.