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7248 (ML7248) high-voltage tetrode. Thoriated tungsten filament. Designed for pulse modulator use.

 

7248 size The valve measures 280x90mm overall and weighs 1.2kg.

This valve is designed to be operated in oil.

Filament voltage 6.3V
Filament current 11.7A
Maximum ratings
DC anode voltage 125kV
DC screen voltage 1500V
DC grid voltage -600V
Peak negative grid voltage -1500V
Pulse cathode current 2A
Anode dissipation 200W
Screen dissipation 20W
Grid dissipation 10W
Typical operating conditions
DC anode voltage 125kV
DC screen voltage 600V
DC grid voltage -360V
Pulse +ve grid voltage 250V
Pulse anode current 1.02A
Pulse screen current 0.27A
Pulse grid current 0.22A
Voltage drop 1200V
Max duty cycle 12%

Markings on the valve are:

National Electronics
ML7248/7248
Made in U.S.A.

149A
83781
9607

Internally, the valve is marked:

Machlett
541971

7248
7248 internals 7248 internals
View of the internals - grid structure on the left and anode on the right.
7248 base 7248 anode connector
The base and the anode connector.
Thanks to John Walker for providing data on this valve

This file was last modified 15:38:17, Saturday November 12, 2011