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Information - Help 
ID = 18551
United States of America (USA)
Brand: RCA (RCA Victor Co. Inc.); New York (NY)
Tube type:  HEPTODE 
Identical to 1680
Similar Tubes
Normally replaceable-slightly different:
  2032 ; 5915 ; 6687 ; 6BY6 ; E91H ; EH900S ; EH960
First Source (s)
1949 : Tube Lore (I)
Production stop 1956
Successor Tubes 2032   EH900S  

Base Miniatur-7-Pin-Base B7G, USA 1940
Filament Vf 6.3 Volts / If 0.3 Ampere / Indirect / Specified voltage AND current AC/DC
Description Designed as logic switching tube: both control grids at 0 V = tube conducts, control grid #1 OR control grid #3 at negative voltage: tube blocked.__[JR]
Pentagrid control (gate) tube, 6BE6 w/ uniform-pitch No. 3 grid to give sharp cutoff at -10 V, w/ treatment to minimize secondary emission. Sold only to IBM and branded "IBM"; replaced 6BE6 in their equipment. Tubes were to be branded w/ IBM part nos. 6B3001 and 303613. Intro. 1949, w/ expected first-year sales of 120,000; withdrawn 1956, in favor of 2032.[Information by L. Sibley] 
Text in other languages (may differ)
1680: Collection JR
Jacob Roschy

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1680: Telefunken Taschenbuch 1971
Anonymous 15 Collector

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from Just Qvigstad

Forum contributions about this tube
Threads: 1 | Posts: 2
Hits: 4225     Replies: 1
1680 (1680) Discovery of an IBM AND gate
Christian ADAM

Dear colleagues,

I recently got the sub assembly shown in attachment one. Thanks to the Rmorg colleagues I could identify the tube as a 1680 made especially for IBM (marked 6B3001). Here the discussion in german:

In the report in attachment two I made the schematic of this AND gate and made a simple demonstrator illustrated in the last photo.

I could find nothind using Google and the greatest help came in this case from Rmorg. Thanks to all contributors.

Who knows more?

Best regards from France,

Christian ADAM



Ernst Erb

Dear Christian
I congratulate you to this well done PDF article in the attachment above. You have also linked to the former article in German. Such linking is very good to get the full picture. The article there is about a sub assembly with the twin triode E92CC. This type was very common as Flip-Flop binary memory (ex Trigger relay) for registers etc. According to Wikipedia the first electronic flip-flop was invented in 1918 by William Eccles and F.W. Jordan. Your module is different and quite interesting.

This reminds me: In 1957 I worked for C.T. Bowring & Co., Ltd. (Leadenhall Street), a Lloyd's broker (underwriter) who was acquired in 1980 by MMC, Marsh & McLennan Companies. There we had a modern tube computer, the BTM1201. Your article made me curious if I can find out something about my former employer. I was only a trainee with very low salary (7 £ 15 s a week) but could work quite some overtime to survive and even save a little bit. I lived in the house of a very kind Landlady in Golders Green and I even biked with my bicycle to the City to save money ... I also still remember when I worked out my route from a book sized street map - not knowing that it lead straight over "Hampstead Heath", the highest hill in London ;-) Well, fortunately I calculated an hour to get to know my way and next time I found the right route ...

By the way: Two companies in Switzerland imported the first computers to Switzerland at about the same time (Spring 1957): IBM 650 for SUVA (Swiss Accidents Insurance) in Luzern and an Univac for Sandoz in Basel.

My stay was limited to one year and I still remember well the place with that punched card equipment and our "queen" the computer model 1201 from British Tabulating Machine Co Ltd (BTM). Now I found a well done article "Early Insurance Broking Applications" which describes what we have done. Very astonishing, such a coincidence. The BTM 1201 (from 1956) and the work being done is described in detail by Ernest Morris who seems to play a part in Computer Resurrection. Calculating with tube computers was soon over, specially when the IBM 1401 arrived which was introduced in 1959 when I worked for IBM in Switzerland.

In my collection are some parts including such a Sub Assembly - but with the ECC92.

End of forum contributions about this tube

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