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1630 /VT128 orbital-beam hexode.

The valve measures 55x50mm overall (25mm across the body)

This valve was used in early SCR-270 radar sets as an electron multiplier preamplifier. Due to noise and reliability issues, it was eventually replaced by a module using 6J4 triodes.

Anode voltage370V
Secondary emitter voltage240V
Outer focusing electrode voltage0V
Inner focusing electrode voltage300V
Grid 2 voltage45V
Grid 1 voltage-1V
Anode current12mA
Secondary emitter current9.5mA
Cathode current3.5mA
Grid 1 to anode transconductance15,000 µmhos
Input capacitance6.5pF
Output capacitance3.5pF

Schematic Diagram of the 1630 internals. The electrons follow the path marked AA under the +ve attraction of focusing electrode J1. They then strike the secondary emitter electrode which gives off electrons at about 5 secondaries for every one primary. These are then attracted to the anode. Varying the potential of focusing electrode J2 causes the beam to follow the path marked as BB and strike the inner focusing electrode.

1630 top view

Above: VT128; below: 1630

1630 inside 1630 inside


Information provided by Bob Weiss; See also Proc IRE V29 No 11 Nov 1941 pp598-602.

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