World Tube Company

NOS and Used
Vacuum Tubes
Love is Resonance!
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UX, CX AND SX DESIGNATIONS OF
THE 1920'S AND 1930'S

The UX and CX designations were used for tubes manufactured in the 1920s and 1930s for radio receivers.

Tubes With 5.0 Volt DC Filaments and Directly Heated Cathodes, Used in 1920s Home Radios Powered by Storage Batteries:

00-A Detector triode with a trace of argon. "00-A" is the number used in most tube manuals. Numbers for earlier versions include UX-200-A and CX-300-A (long pins, push-in socket) and UV-200-A (stub pins, bayonet socket).

01-A All-purpose low-mu triode, used as RF amplifier, detector, AF amplifier and power triode. The most popular tube of the 1920s. "01-A" is the number used for replacements manufactured after 1930 and in tube manuals. Numbers for early versions include UX-201-A and CX-301-A (long pins, push in socket) and UV-201-A (stub pins, bayonet socket).

Note: There were four tubes in the "01" series, each with different current ratings for their filaments. Type 01-A was the most commonly used.

Types UV 201 and UX 201 - 1.0 ampere
Type 01-A (UV 201-A, UX 201-A, etc.) - 250 milliampere
Type UX 201-B - 125 milliampere
Type UX 201-C - 60 milliampere

12-A Medium-mu triode, often used as detector, audio driver or audio output, but not as an RF amplifier - "12-A" is number used for replacements manufactured after 1930 and in tube manuals. Also referred to as 112-A. Many early versions are marked UX-112-A or CX-112-A.

Tubes With 2.0 volt DC Filaments and Directly Heated Cathodes, Used in 1930s Home Radios Powered by Storage Batteries:

19 Dual power triode -- also used in "farm radios" with 6-volt vibrator power supplies.

20 Power triode - Early versions numbered UX-220

22 Sharp-cutoff tetrode - Early versions numbered UX-222

30 Medium-mu triode - Early versions numbered UX-230. Can also be used as an power triode. An upgraded version of type 01-A.

31 Power triode - Early versions numbered UX-231

32 Sharp-cutoff tetrode - Early versions numbered UX-232

33 Power pentode - Early versions numbered UX-233

34 Remote-cutoff tetrode - Early versions numbered UX-234

49 Dual-grid power triode, similar to type 46

Tubes With 3.3 volt DC Filaments and Directly Heated Cathodes, Used In 1920s Home Radios Powered by Dry Cells (filaments) and Storage Batteries (B-plus voltage):

V99 Low-mu triode, except for stub-pin bayonet base and pinout, electronically identical to X99.

X99 Same as V99, but with standard pins and different basing arrangement.

Tubes With DC Heaters and Indirectly Heated Cathodes:

15 Sharp-cutoff pentode, used in "farm radios."

48 Power tetrode, used in 32-volt "farm radios.'" When two are parallel-connected, they can operate with plate and screen voltages as low as 28 volts.

Tubes With Directly Heated Cathodes, Used Only With AC power Supplies:

10 Power triode - Early versions numbered UX-210

26 Medium-mu triode, used in early AC radio receivers manufactured in the late 1920s - Early versions numbered UX-226

45 Power Triode - Early versions numbered CX-345, SX-245 and UX-245

46 Dual grid power triode - Grids 1 and 2 connected together for use as push-pull Class B outputs, Grid 2 and plate connected together for use \as single-tube audio driver - Early versions numbered UX-246

47 Power pentode - Early versions numbered UX-247

80 Full-wave rectifier (electronically identical to type 5Y3) - Early versions numbered UX-280 or CX-380

Tubes With Indirectly Heated Cathodes, Used Only With AC Power Supplies. (Except for Type 42, All Have 2.5 volt heaters.):

24 Sharp-cutoff tetrode - Early versions numbered UX-224 and CX-324

24-A an upgraded version of type 24 - Early versions numbered UX-224A and CX-324A

27 Medium-mu triode - Early versions numbered UX-227 and CX-327. The first North American tube with an indirectly heated cathode, which is necessary for detector circuits in AC powered tube radios.

35 Remote-cutoff tetrode (Commonly branded as 35/51) - Early versions numbered UX-235

42 Power pentode, earlier UX6 base version of type 6F6. Except for 6.3 volt heater, identical to types 2A5 and 18.

51 same as type 35 (Commonly branded as 35/51)

Tubes With Directly Heated Cathodes, Used With AC, DC or Home-based Storage Battery Power Supplies (1927-1931)

71-A Power triode - "71-A" is number used for replacements manufactured after 1930 and in tube manuals. Also referred to as 171-A. Many early versions numbered UX-171-A or CX-171-A.

Tubes With Indirectly Heated Cathodes, Used With AC, DC, AC/DC or Automobile-based Storage Battery Power Supplies:

36 Sharp-cutoff tetrode - Early versions numbered UX-236

37 Medium-mu triode - Early versions numbered UX-237

38 Power pentode - Early versions numbered UX-238

39 Remote-cutoff pentode, often branded as 39/44 - Early versions numbered UX-239

41 Power pentode, earlier UX6 base version of octal type 6K6.

43 Power pentode, earlier UX6 base version of octal type 25A6.

44 Same as type 39

75 Dual-diode, high-mu triode. Earlier UX6 base version of octal types 6B6-G and 6SQ7, and 7-pin miniature type 6AV6.

77 Sharp-cutoff pentode, earlier UX6 base version of octal type 6J7.

78 Remote-cutoff pentode, earlier UX6 base version of octal type 6K7.

84 Full-wave rectifier with indirectly heated cathode, often branded as type 84/6Z4. Earlier UX6 base version of octal type 6X5 and 7-pin miniature 6X4.

85 Dual-diode, medium-mu triode, earlier UX6 base version similar to octal types 6R7 and 6SR7 and miniature types 6BF6 and 6BU6.

Rarely Used Tubes:

14 Same as type 24-A but with a 14 volt, 300 milliampere heater. Used in Philco models 46 and 46E

17 Same as type 27 but with a 14 volt, 300 milliampere heater. Used in Philco models 46 and 46E

18 Same as types 2A5 and 42 but with a 14 volt, 300 milliampere heater. No known commercial use.

29 Wunderlich detector

52 Dual grid power triode similar to types 46 and 49. Has 6.3 volt filament. Most commonly used in early car radios.

64 Sharp-cutoff tetrode (Except for 400 milliampere heater, identical to type 36)

65 Remote-cutoff pentode (Except for 400 milliampere heater, identical to type 39)

67 Medium-mu triode (Except for 400 milliampere heater, identical to type 37)

68 Power pentode (Except for 400 milliampere heater, identical to type 38)

69 Wunderlich detector

70 Wunderlich detector used in Mission Bell model 19 car radio.

90 Wunderlich detector

92 Wunderlich detector

95 Original number of type 2A5

181 Power triode

182-B Same as type 482-B below.

183 Same as type 483 below.

213 Early version of type 80 - Often numbered UX-213

216 Early half-wave rectifier - Often numbered as UX-216

482-B Power triode with directly heated cathode. Used in Sparton AC radios, circa 1929. Replacements often numbered 182-B/482-B. Similar to type 71-A, but with higher plate voltage.

483 Power triode with directly heated cathode. Used in Sparton AC radios, circa 1929. Replacements often numbered 183/483. Similar to type 45, but with a 5.0 volt, 1.25 ampere heater.

485 Medium-mu triode with indirectly heated cathode. Used in Sparton AC radios, circa 1929. Similar to types 56 and 76, but with a 3.0 volt, 1.25 ampere heater, and lower plate voltage.

950 Power pentode with directly heated cathode, used in storage battery home radios with 2.0 volt filament supply. Similar to type 1F4.

951 Sharp-cutoff pentode with directly heated cathode, used in storage battery home radios with 2.0 volt filament supply. Similar to type 1B4-P. ______________________________________________________________________________________________

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