Two Digit Types From 1 to 100

You may have wondered why there are gaps in the numerical listing of tube numbers between 1 and 100. Most of us are familiar with the more common types like 24A, 26, and 27. But what happened to 25? The following listing contains some unusual types. Very short descriptions are given for common types. Notes: 1. The two digit designation is given here. Although many were issued as three digit numbers (e.g. UX213), they appear in later books and substitution lists as two digit numbers (e.g. '13 or 13). 2. The UV prefix indicates the base with four short pins (also called the Navy base). The UX prefix indicates four long pins, and the UY prefix indicates the standard five pin base. 3. Philco/Sylvania sold ballast tubes numbered 2 through 9 not listed here. 4. RF = radio frequency and mu = amplification factor.

00A Triode. Originally made by GE for RCA in late 1920 as the UV200 which had a 5V, 1A tungsten filament. Intended for use as a soft (slightly gassy) detector, it contained argon gas at a pressure of .05mm of mercury. The UX200A was introduced in 1926. the 200A differs from the 200 in that the 200A uses cesium vapor instead of argon and has a 5V, .25A filament.

01A Triode. Originally made by GE for RCA in late 1920 as the UV201 which had a pure tungsten 5V, 1A filament. A Westinghouse version, made briefly, was tubular with a 4V, .8A rating (essentially a rebased WR21), then, Westinghouse standardized their production. The UV201A with a 5V, .25A thoriated filament was introduced in 1922 and UX201A tubes were introduced in 1925.

1 Rectifier. RCA's type 1 is the mercury vapor version of the 1-V rectifier, and is equivalent to KenRad's type KR-1. As far as I know, the only published data for the type 1 is in the suppliment to RCA's receiving tube manual R-10.

The other early numbers in this series (202 through 209) were transmitting tubes of RCA or Western Electric, and the two digit designations between 2 and 10 were never applied to receiving tubes (although 1 through 9 were Philco ballasts).

10 Power triode.

11 Triode. 1930s era tube characteristic lists mean WD-11 when "11" is listed. This dry cell tube was introduced in 1922 and was originally made by Westinghouse for RCA. It has a unique four pin base with one large pin and three smaller pins. Its principal use was in the Radiola III and IIIA.

12 Triode. 1930s era tube characteristic lists often mean WD-12 when "12" is listed. This dry cell tube was introduced in 1923 and was originally made by Westinghouse for RCA. It is essentially a WD-11 on a standard UV base (four short pins). The WX-12 was issued in 1926, and is the same tube on a standard UX base (four long pins). Not to be confused with the UX112 or 112A.

12A Power triode. Originally released as the UX112 in 1925, the 112 had a 5V, .5A filament, and was soon replaced by the 112A with a 5V, .25A filament. This is the power amplifier version of the 01A.

13 Full wave rectifier. Originally issued by GE as the UV213 in 1924, then as the RCA UX213, this was the forerunner of the type 80. The 13 and 80 are similar in characteristics, except that the 13 does not deliver as much current. So, you can substitute an 80 for a 13, but not a 13 for an 80.

14 Screen grid tetrode. The 14 was made by Sylvania for Philco, and is a 14V filament version of the type 24A. This was used in the Philco model 46 set designed for 110V DC operation.

15 RF Pentode. introduced by Sylvania, but made by many others, this tube was used as a combined first detector/oscillator in early 1930s superheterodynes.

16 Half wave rectifier. RCA issued the type UV216 in 1921 as the rectifier version of the type UV202 transmitting tube. The UX version, the UX216B or 16B was introduced in 1925 The 16B was used in the first AC radiolas, and it was the forerunner of the 81. The 16B and 81 are similar in characteristics, except that the 16B does not deliver as much current. So, you can substitute an 81 for a 16B, but not a 16B for an 81. Both RCA and Perryman both made a 216A briefly, but the numbers were dropped to avoid confusion with the Western Electric 216A.

17 Triode. The 17 was made by Sylvania for Philco, and is a 14V filament version of the type 27. This was used in the Philco model 46 set designed for 110V DC operation.

18 Power pentode. The 18 is a 14V filament version of the type 42 introduced by Sylvania. It was designated for use as an output tube in transformerless sets, but was supplanted by the type 43, whose 25V filament was better suited for the purpose.

19 Twin triode (high mu). A 2V tube designed for class B audio. The 1J6 is the octal equivalent.

20 Power triode. Originally issued as the UX120, this is the audio output version of the UX199, and it bears the same relationship to the 99 as the 12A does to the 01A.

21 Triode. The RCA UX221 was the export version of the UX201A. It has the same characteristics as a 201A, except that it only has a filament current of .06A. The Canadian 201C is equivalent.

22 Screen grid tetrode. This was the first screen grid tube. Designed for RF amplification, its directly heated 3.3V, .13A filament was meant for battery sets.

23 No known use.

24 Screen grid tetrode. The first AC screen grid tube. The 24A is an improved version.

25 Triode. UX (later UY) 225 was RCA's developmental type number for the type 27. The few that are known either have an unusual five pin base or a standard four pin base with a cap on top.

26 Triode. Essentially designed as an 01A for AC.

27 Triode. Cathode type intended for use as a detector. One of the first AC tubes.

28 Sold by the Shamrock Tube Company, this was a high mu version of the 27.

29 Double grid detector. Originally sold by Sylvania as the 229, and then just 29, this 2.5V tube was equivalent to the Wunderlich A made by Arcturus.

30 Triode. 2V, .06A general purpose tube for portable receivers. Can replace the 99 if the filament voltage is dropped. Originally issued as a tubular tube like the 99, then S-12 and later ST-12 bulbs were adopted.

31 Power triode. 2V, .13A power tube for portable receivers. Can replace the 20 if the filament voltage is dropped. Originally issued as a tubular tube like the 20, then S-12 and later ST-12 bulbs were adopted.

32 Screen grid tetrode. 2V, .06A designed for battery sets.

33 Power pentode. 2V, .26A designed for battery sets.

34 RF pentode. 2V, .06A designed for battery sets.

35 Screen grid tetrode. This tube was RCA's response to the variable mu 551, and is essentially a variable mu type 24A. The types 35 and 51 were so similar that the type numbers were merged to 35/51. See 51.

36 Screen grid tetrode designed for automobile receivers.

37 Triode designed for automobile receivers.

38 Power pentode designed for automobile receivers.

39 RF Pentode. See 44.

40 Triode. High mu equivalent of the 01A designed for resistance coupled circuits.

41 Power Pentode. The 6K6 is the octal equivalent.

42 Power pentode. The 6F6 is the octal equivalent. The 2A5 is the 2.5V version.

43 Power pentode. 25V tube designed for transformerless sets. The 25A6 is the octal equivalent.

44 RF Pentode. Same as type 39 with a higher cutoff. The characterisics were similar enough that the types were combined to 39/44. Several companies, among them Raytheon, National Union, and Sylvania made both a 39 and a 44.

45 Power triode.

46 Power tetrode. Similar to the 47, except that no suppresser grid is provided.

47 Power pentode. Similar to type 46, except that the 46 has no suppresser grid.

48 Power tetrode. 30V, 0.4A filament. Was used mostly in theater amplifiers.

49 Power tetrode. 2V, 0.12A filament.

50 Power triode. As the S-21 sized globe or the ST-19 bulb, this was the largest tube used in home receivers.

51 Screen grid tetrode. Originally issued as the 551 by Arcturus, this was the first variable mu tube. This tubes characteristics were very similar to the type 35, and eventually the two types were merged as type 35/51. Several companies, among them Raytheon and Sylvania made both a 551 and a 235.

52 Dual grid triode. This tube was introduced by Raytheon.

53 Twin triode. The 6A6 is the 6.3V version.

54 Not a receiving type. When seen, usually refers to a Heinz and Kaufman transmitting type.

55 Duodiode triode. The 85 is the 6.3V version. The 75 is similar to both the 55 and the 85, except that the triode sections of the 55 and 85 have a mu of 8.3, while that of the 75 has a mu of 100.

56 Triode. Similar to type 27, except has a higher mu (13.8 vs 9) and draws less current (1A vs 1.75A).

57 Sharp cutoff RF pentode. The 6C6 is the 6.3V version.

58 Remote cutoff RF pentode. The 6D6 is the 6.3V version.

59 Power pentode.

59B Power pentode. Filamentary version of type 59 used in Majestic receivers.

60 No known use.

61 No known US use. There is apparently a Japanese type 61.

62 No known US use. There is apparently a Japanese type 62.

63 No known US use. There is apparently a Japanese type 63.

64 Screen grid tetrode. The National Union types 64, 65, 67, and 68 were the original 6.3V tubes designed for automobile radios. All were rated for 6.3V, .4A service. All of these tubes that I have seen are S-14 globes (the size of a globe 24A). The 64, 65, 67, and 68 were reissued as the 64A, 65A, 67A, and 68A with S-12 bulbs (the size of a globe 56). The 64 was supplanted by the type 36 which is equivalent, except for the 6.3V, .3A filament. The "A" version is equivalent to a 36.

65 RF pentode. The 65 was supplanted by the type 39/44 which is similar, except for the 6.3V, .3A filament. The "A" version is equivalent to a 39/44. See type 64.

66 Not used for receiving tubes. Sometimes used to refer to the 866 rectifier. I have seen an 866 made by Hytron that just has "66" printed within the octagon on the glass.

67 Triode. The 67 was supplanted by the type 37 which is equivalent, except for the 6.3V, .3A filament. The "A" version is equivalent to a 37. See type 64.

68 Power pentode. The 68 was supplanted by the type 38 which is equivalent, except for the 6.3V, .3A filament. The "A" version is equivalent to a 38. See type 64.

69 Double grid detector. Made by Sylvania, this 6.3V tube was equivalent to the Wunderlich A Auto made by Arcturus.

70 Double grid detector. Made by Sparton, it is a "Wunderlich type", but not similar in characteristics to the Arcturus or Sylvania tubes. This was used in the Sparton model 34 automobile receiver.

71A Power triode. Originally issued as the UX171 with a 5V, .5A tungsten filament, it was soon replaced by the UX171A with a 5V, .25A oxide filament. Sylvania made special 10V filament type 171s that were used in a DayFan 110V DC set.

72 Not used for receiving tubes. When listed, usually refers to Raytheon RK-72 rectifier.

73 Not used for receiving tubes. When listed, usually refers to Raytheon RK-73 rectifier.

74 Not normally used for receiving types. Infrequently used in reference to the type 874 voltage regulator.

75 Duodiode triode. The 2A6 is the 2.5V version. See also type 55. A 6F5 triode and 6H6 duodiode are together equivalent to a 75.

76 Triode. 6.3V version of type 56. The 6P5 is the octal equivalent.

77 Sharp cutoff RF pentode. The 6J7 is the octal equivalent.

78 Remote cutoff RF pentode. The 6K7 is the octal equivalent.

79 Twin triode. 6Y7G is the octal equivalent.

80 Full wave rectifier. 5Y3G or GT is the octal equivalent.

81 Half wave rectifier. Simply a type 50 with no grid.

82 Full wave mercury vapor rectifier. The 82 is a 2.5V version of the 83, and handles only half the power.

83 Full wave mercury vapor rectifier. The 83 is a 5V version of the 82, and handles twice the power.

83V Full wave rectifier. A high vacuum version of the 83, but not usually interchangeable due to lower ratings. 5V4 is the octal equivalent.

84 Full wave rectifier. Also known as the 6Z4.

85 Duodiode triode. See type 55.

86 No known use, although JRC did issue a mercury vapor rectifier type 986 which is sometimes referred to as type '86. There is an 86M Canadian type.

87 No known US use. There is an 87M Canadian type

88 Full wave rectifier. This mercury vapor tube was originally issued by Perryman as the 588, and was intended as a mercury vapor substitute for the 80. There is also a Canadian type 88S.

89 Power pentode. Most often seen as 89Y, the "Y" suffix indicating a low loss (usually micanol) base.

90 Double grid detector. Made by KenRad, this 2.5V tube was equivalent to the Wunderlich A made by Arcturus. KenRad also sold this type as the KR-20.

291 Twin triode. This is the 12.6V version of the Speed 295. See 295. Note that RCA sold an industrial thyratron as a type 91.

92 Double grid detector. Made by KenRad, this 6.3V tube was equivalent to the Wunderlich A Auto made by Arcturus. KenRad also sold this tube as the type KR-22.

293 Twin triode. This is the 6.3V automobile version of the Speed 295. See 95.

94 KenRad type.

95 Power pentode. This is equivalent to a 2A5. KenRad sold this as the KR-25.

295 Twin triode. Originally issued by Speed (Cable Supply Co.) as the 295 "triple twin". This is essentially a 27 coupled to a 45 in one envelope.

96 Half wave rectifier. Made by KenRad, this 10V mercury rectifier.

97 No known use.

98 Full wave rectifier. This 6.3V mercury vapor tube was equivalent to and essentially replaced by the vacuum type 84. KenRad also sold this tube as the type KR-28.

99 Triode. General purpose battery triode originally made by GE for RCA and issued as the UV199, later UX199.