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Sensibly equivalent to:
BT107 KU54
See also:
AEI Catalogue
Extras ▼


The CV3875 is a triode hydrogen Thyratron for power switching. The prototype was the American KU54 but this AEI device also carries the Type designation of BT107 the reference above is a PDF of the AEI catalogue. It is believed that this was designed for a ground based Radar system. If so it would deliver HT pulses to the magnetron
James Kyle rescued this valve and donated it to the museum. It was new in its original packing when James saved it. However, My Hermes managed to drop it so hard that it broke apart in transit.
The Thyratron was at 14MU the local name for No. 14 maintenance unit of the RAF. Originally this was RAF Carlisle.
The base: the wide internal tube provides the glass to metal seals for the electrodes passing through and also is the site of the clamp the secures the screen. The wires are colour coded - yellow: heater, black/yellow: heater- reservoir, black: cathode, red: reservoir, green: grid.
The anode connection is made to the top cap. The anode connection is encased in glass and the top of the envelope is made re-entrant to place the strength of the support close to the internal anode. Note the white lettering of AEi and BT107.
The lower part of the envelope has a wide tube that ends in the evacuation pip. The structure it contains is the hydrogen reservoir that is separately heated during operation.
The main component in the main envelope is the screen that shields the outside from any generated X-rays.
This image shows the amount of internal distortion caused in transit.
The package as delivered with the end opened. The crush to the top right of the cardboard is where the impact took place. The base was at this end.
This is the image James sent me with the original email. It shows the perfect condition of this heavy duty valve.
The wide glass tube envelope is 129 mm in diameter, and excluding the base leads is 312 mm tall.
Reference: Data-sheet.


Absolute Maximum Operating Conditions
The Thyratron
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 14, 2019.
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