Tubes manufactured for military contracts
United States Signal Corps
Signal Corps. SE-1444 variants:Based on snippets of information from Gerald Tyne's survey, various media references, and physical evidence; it is pretty safe to say that there were no more than 30,000 of the SE-1444 manufactured.
The original order of 25,000 from the US military seems accurate, in that examples have not been identified with serial numbers above #26244. Low serial numbers do not use leading zeros, and the brass Shaw bases are unmarked.
In operations, these were specified by current rather than voltage, and were intended to operate with a filament at 0.65amp +/-20% @ 4-5v DC. Once nice and warm, these could produce 10w with 750v DC applied to the plate.
Moorhead's production approaches hint that he built tubes in stages, and in large batches - likely to improve consistency and gain economy of scale.
Serialization of tubes with acid etching was done specifically for the needs of the military. Consumers had no need for it, but it allowed inventory and tracking of expensive tubes assigned into the field and likely replaced after short service.
My guess: originally Moorhead handed off tubes numbered #1-25000. In receipt, the government found additional 'fallout' of tubes that were returned. An additional 1-2000 tubes were likely made and numbered as replacements to satisfy the contract.
Greater scarcity than the VT and based ER tubes.
What can we deduce about the SE-1444 tubes and contract?
- WWI began 6-Apr-1917 for the United States
- Immediately prior, the lab was making tubular 'Electron Relays', the Moorhead 'Special' and something called the Moorhead 'Amplifying Coil'
- The SE-1444 would be the first based tube produced by Moorhead, leveraging the base of the Shaw Insulator Co.
- Moorhead supplied the British military with 40,000 'type R' tubes (receiving), and 10,000 'type B' tubes (transmitting)
- WW1 ends 11-Nov-1918, leaving the military with a significant stock of unused SE-1444 tubes.
Production rates are tricky to estimate but are at the heart of the story. Even with production efforts batching everything possible for efficiency, there was a 'long pole' in the tent that couldnt (yet) be shortened.
Evacuation to a high degree was required, and even running 24/7 it was only possible to evacuate a certain number per day.
(2) orders of 25k to the British, & (2) orders of 25k to the USA were delivered. Given that they produced these within 18mos, their output rate must have exceeded 185 tubes/day. With high failure rates, this might have actually been closer to 200/day.
As a collector, I have seen perhaps 8 of these offered for sale in 5ys. Serial numbers that have appeared are unusually low, and I have never seen an SE-1444 with a five digit serial number. Examples may be those taken as souveniers by soldiers in the Signal Corps.
I dont believe any SE-1444s ever made it into the surplus market like the General Electric CG-1162s.
- Radio Retailing, Jun-1929, pg. 267. From AmericanRadioHistory.com. Retrieved 30-Nov-2018. !
- Radio Broadcast, Dec-1929, pg. 123. From AmericanRadioHistory.com. Retrieved 30-Nov-2018. !