The Moorhead series D (D. to avoid confusion with Type D) triode dates from 1920 but the original design of electron relay is earlier. Patent problems existed and RCA licensed Moorhead in 1921 to make a limited number of Tubes. This number was completed in 1922.![](../pics/abo0010h.jpg)
The Moorhead name on the base cap.![](../pics/abo0010a.jpg)
The date information for this valve comes from the attached label.![](../pics/abo0010b.jpg)
The anode is a bright plate 18 mm across and folded at the top. The grid is wound on glass supports that are integral with the pinch.![](../pics/abo0010c.jpg)
The structure can be seen to include the glass grid support piercing the anode to give the anode a top support.![](../pics/abo0010d.jpg)
The grid and anode end on.![](../pics/abo0010e.jpg)
The filament is a single inverted V and has corrugations that may be there to compensate for length variation when hot.![](../pics/abo0010f.jpg)
A better view of the filament.![](../pics/abo0010g.jpg)
The Bakelite base with brass connections.The wide glass tube envelope is 26 mm in diameter, and including the base is 116 mm tall.Reference: 1047. Type D. was first introduced in 1919. See also 1919 adverts. |
Updated January 18, 2022.
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