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ID = 50751
United States of America (USA)
Brand: Moorhead Laboratories (Pacific); San Francisco
Developer: Moorhead Laboratories (Pacific); San Francisco 
Tube type:  Gas Triode   Detector 
  <1925 very rare. ***
Identical to ER_Moorhead = ER_Marconi
Similar Tubes
Normally replaceable-slightly different:
First year Jul.1916 Saga of the Vacuum Tube, Tyne page 167
Predecessor Tubes Moorhead_1  
Successor Tubes Moorhead_Ext_Grid   ER_Moorhead-1917  

Base UV-Base (4 Pins+Bayonet, USA 1914 WE)
Was used by Radio/TV-reception etc.
Filament Vf 4 Volts / If 0.7 Ampere / Direct / Battery =

The 1916 version of the ER (Electron Relay) was unmarked but can be identified by the press construction and length to width ratio. There are two versions: Single or double filament. Moorhead made a predecessor in 1915 but this is not known because no ads were made and only few were sold. Most ER you find are marked as such - see ER_Moorhead-1917. Anode 18-40 Volt
. The base on this tube was made by the Shaw Insulator Company, which was associated with Moorhead laboratories.

Dimensions (WHD)
incl. pins / tip
44 x 102 x 35 mm / 1.73 x 4.02 x 1.38 inch
Tube prices 3 Tube prices (visible for members only)
Information source Saga of the Vacuum Tube, Tyne   Pages 170-174
-- Collector info (Sammler)   

2a_uv4~~6.png ER_Moorhead: own collection
Peter den Boer

Just Qvigstad

Collection of




Anode is considerably longer. Bulb and base measures are unchanged.

Forum contributions about this tube
Threads: 1 | Posts: 1
Hits: 1974     Replies: 0
First picture of the Moorhead Electron Relay
Alan Larsen

The August 1916, issue of The Electrical Experimenter magazine was the first advertisement to offer a picture of the 1916 Moorhead Electron Relay. As noted in the advertisement, the tube was available with either a single filament or a double filament for $1.50 more.

At this time Moorhead was advertising under the name of Pacific Laboratories.


End of forum contributions about this tube

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