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33
Power Amplifier Pentode

EIA Base & Outline

EIA Base: 5KEIA Bulb: 14-0
Source ........................................ RCA R-10 - 1932

33
Power Amplifier Pentode

EIA Base: 5KEIA Bulb: 14-1
Source ........................................ RCA RC-13 - 1937

Application

Source ........................................ RCA R-10 - 1932
The '33 is a power amplifier pentode for use in the output stage of battery-operated receivers. The low filament current required by the '33 makes this tube particularly applicable for use in combination with the '30, '32, and/or '34 in radio sets where economy of battery consumption is important.

The '33 is capable of producing greater power output than three-electrode power amplifiers of the same plate current drain. Furthermore, this tube has the design feature of greater amplification than possible in a three-electrode amplifier without serious sacrifice in power output.

The power-handling ability of the '33 is made possible by the addition of both a suppressor and a screen between the grid and plate. The suppressor is placed next to the plate and is connected inside the tube to the filament. This design practically eliminates the secondary emission effects which limit the power output from four-electrode screen tubes.

Mechanical Data

Source ........................................ RCA R-10 - 1932
Bulb .......................................... S-14
Base Type ..................................... Medium 5-Pin
EIA Outline ................................... 14-0
EIA Base ...................................... 5K
Mounting Position ............................. Vertical

Source ........................................ RCA RC-13 - 1937
Bulb .......................................... ST-14
EIA Outline ................................... 14-1

Electrical Data

Source ........................................ RCA R-10 - 1932
Filament Voltage .............................. 2.0 DC V
Filament Current .............................. 0.26 A

Direct Interelectrode Capacitances (approx)

Pentode
Source ........................................ RCA R-10 - 1932
Input ......................................... 8.9 pf
Output ........................................ 11.1 pf
Grid to Plate ................................. 0.9 pf

Pentode
Source ........................................ RCA RC-13 - 1937
Input ......................................... 8.9 pf
Output ........................................ 11.0 pf
Grid to Plate ................................. 0.9 pf

Maximum Ratings (Design Center Values)

Pentode
Source ........................................ RCA R-10 - 1932
Plate Voltage ................................. 135 V
Grid No. 2 Voltage ............................ 135 V

Pentode
Source ........................................ RCA RC-13 - 1937
Plate Voltage ................................. 180 V
Grid No. 2 Voltage ............................ 180 V

Characteristics and Typical Operation

Class A Amplifier
Source ........................................ RCA R-10 - 1932
Plate Voltage ................................. 135 V
Grid No. 2 Voltage ............................ 135 V
Grid No. 1 Voltage ............................ -13.5 V
Grid No. 1 Voltage Derived from
Cathode Bias Resistor ...................... 770 Ω
Amplification Factor .......................... 70
Plate Resistance (approx) ..................... 50K Ω
Transconductance .............................. 1450 µMho
Plate Current ................................. 14.5 mA
Grid No. 2 Current ............................ 3 mA
Load Resistance ............................... 7K Ω
Power Output (approx) ......................... 0.7 W

Class A Amplifier
Source ........................................ RCA RC-13 - 1937
Plate Voltage ................................. 180 V
Grid No. 2 Voltage ............................ 180 V
Grid No. 1 Voltage ............................ -18 V
Grid No. 1 Voltage Derived from
Cathode Bias Resistor ...................... 670 Ω
Amplification Factor .......................... 90
Plate Resistance (approx) ..................... 55K Ω
Transconductance .............................. 1700 µMho
Plate Current ................................. 22 mA
Grid No. 2 Current ............................ 5 mA
Load Resistance ............................... 6K Ω
Power Output (approx) ......................... 1.4 W

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Thu, 18 Aug 2022 10:39:24 -0700