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D-401A

Sensibly equivalent to:
CX301A D-01A UX201A
See also:
DV and DL valves
    
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The D-401A replaced the D-01A in 1928. The performance was essentially identical but the physical design followed the competition with a balloon envelope and a Bakelite base cap.
The original De Forest box.
Thanks to Joe Gruber for sending the images.
The balloon envelope is 45 mm in diameter and, including the UX4 base pins, is 117 mm tall.
Reference: Joe Gruber. Type D-401A was first introduced in 1928.

 

Pin Connections
UX4
1
2
3
4
g1
a
f
f

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
5.0
0.25
Updated November 14, 2020.
shape:balloon construction:pinch type:triode age:1920.1930 base:ux4 heater:5.0v pins:4 pin:1.g1 pin:2.a pin:3.f pin:4.f
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