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51

Information - Help 
ID = 2678
       
Country:
United States of America (USA)
Brand:
Tube type:  Screen-grid Tetrode   RF/IF-Stage   Controlling (mu) 
Identical to 51 = 35/51 = RENS351 = 551 = 435 = G-51 = Z51 = NU-35-51 = T-35 = C-51 = VT-35 = 451_deForest = SY235 = T-51 = RYB551 = CV1752 = 35
Similar Tubes
Other shape (e.g. bulb type):
  51S ; 551S ; G-51-S
Normally replaceable-slightly different:
  251 ; AC51S ; C-51-S ; Y251_Hytron ; ac551_Rogers
Other class quality (otherwise equal):
  NU-35/51S
Other base:
  51_Coronet
First year May.1931 -- Collector info (Sammler)
First Source (s)
May.1931 : 70 Years of Radiotubes and V.
Dec.1930 : IRE paper December 1930
Successor Tubes 1932   58   35/51   ac551_Rogers  
Base UY-Base, 5 Pins (USA, April 1927) (Codex=Ha) Top contact with a cap.
Filament Vf 2.5 Volts / If 1.75 Ampere / Indirect / Specified voltage AC/DC
Description In 1929 begins the problem of cross modulation in the USA caused by strong signals of similar frequency and nonlinearities in the first stage. Stuart Ballantyne and Harold A. Snow (Boonton Research Corp.) found a first answer with the tube 551 later called 51 (Arcturus, Majestic, Raytheon May 1931) with "gradual cut-off" (vari-mu, gradual cut-off, GE experimented in 1919 in vain). Probably first publ. IRE paper December 1930. Soon after the 551 RCA came with the same tube called UY235 (235 later 35 and later joined as 35/51, in Japan UY-235). An article, June 1931 in "National Radio News" shows how necessary they were. In short: Trade show in Chicago in 1931 73% pentode and 94.5% variable-mu tubes. In the same year Philips brought the E445 and Cossor the 220VSG. This was a "super control feature for AVC" as Silver-Marshall stated for model 726. The problem: a great negative voltage is necessary and therefore a special AVC tube is involved for the RCA solution. See General Motors model 220 S-10B (1931). Philco used the Wheeler invention (released Oct. 1929) with its model 95 Screen Grid (1929) where a UY-227 triode works as a combination: detector and AVC diode. 
Tube prices 1 Tube prices (visible for members only)
Information source Taschenbuch zum Röhren-Codex 1948/49   
448_9~~1.png 51: Telefunken Werkstattbuch
Wolfgang Bauer

Just Qvigstad
Usage in Models 10= 1931?? ; 26= 1931? ; 168= 1931 ; 8= 1932?? ; 26= 1932? ; 48= 1932 ; 2= 1933?? ; 5= 1933? ; 16= 1933 ; 4= 1934?? ; 2= 1934? ; 1= 1934 ; 1= 1935?? ; 1= 1935? ; 3= 1935 ; 2= 1938? ; 1= 9999? ; 1= 9999
Quantity of Models at Radiomuseum.org with this tube (valve, valves, valvola, valvole, válvula, lampe):325

Collection of

Georges Werts (B)
Christian Schaufelberger (CH)
Peter den Boer (NL)
Karlheinz Fischer (D)
Peter Steffen (CH)
Dejan Momirov (RS)
 
51.jpg

51
 

Variants

Dome type, clear glass.
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