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38
Power Pentode

EIA Base & Outline

EIA Base: 5FEIA Bulb: 12-01
Source ........................................ RCA R-10 - 1932

38
Power Pentode

EIA Base: 5FEIA Bulb: 12-6
Source ........................................ RCA RC-13 - 1937

Application

Source ........................................ RCA R-10 - 1932
The '38 is a power amplifier pentode for use in the output stage of automobile receivers and in sets operated from d-c power lines. It is capable of giving a large power output for a relatively small input signal voltage. The '38 contains a heater-cathode which is designed for d-c operation. Its design permits uniform tube operation over a comparatively wide range of heater voltages without appreciably affecting either performance or serviceability of the tube. This feature, together with that of the general freedom from microphonic and battery circuit disturbances makes the '38 well suited to mobile service and other applications where complete d-c operation is desirable.

Mechanical Data

Source ........................................ RCA R-10 - 1932
Bulb .......................................... S-12
Base Type ..................................... Small 5-Pin
EIA Outline ................................... 12-01
EIA Base ...................................... 5F
Top Cap ....................................... Small Metal
Mounting Position ............................. Any

Source ........................................ RCA RC-13 - 1937
Bulb .......................................... ST-12
EIA Outline ................................... 12-6

Electrical Data

Source ........................................ RCA R-10 - 1932
Heater Voltage ................................ 6.3 DC V
Heater Current ................................ 0.3 A

Source ........................................ RCA RC-13 - 1937
Heater Voltage ................................ 6.3 V
Heater Current ................................ 0.3 A

Direct Interelectrode Capacitances (approx)

Pentode
Source ........................................ RCA R-10 - 1932
Input ......................................... 4.1 pf
Output ........................................ 8.5 pf
Grid to Plate ................................. 0.3 pf

Pentode
Source ........................................ RCA RC-13 - 1937
Input ......................................... 3.5 pf
Output ........................................ 7.5 pf
Grid to Plate ................................. 0.30 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 ................................. 250 V
Grid No. 2 Voltage ............................ 250 V
Grid No. 1 Circuit Resistance
Fixed Bias ................................. 500K Ω
Self Bias .................................. 1M Ω

Characteristics and Typical Operation

Class A Amplifier
Source ........................................ RCA R-10 - 1932
Plate Voltage ................................. 100 V
Grid No. 2 Voltage ............................ 100 V
Grid No. 1 Voltage ............................ -9 V
Amplification Factor .......................... 80
Plate Resistance (approx) ..................... 84K Ω
Transconductance .............................. 950 µMho
Plate Current ................................. 7 mA
Grid No. 2 Current ............................ 2.0 mA
Load Resistance ............................... 8.5K Ω
Power Output (approx) ......................... 0.2 W
Total Harmonic Distortion ..................... 8 %

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 ...................... 1200 Ω
Amplification Factor .......................... 100
Plate Resistance (approx) ..................... 102K Ω
Transconductance .............................. 975 µMho
Plate Current ................................. 9 mA
Grid No. 2 Current ............................ 2.5 mA
Load Resistance ............................... 13.5K Ω
Power Output (approx) ......................... 0.525 W
Total Harmonic Distortion ..................... 10 %

Class A Amplifier
Source ........................................ RCA RC-13 - 1937
Plate Voltage ................................. 100 V
Grid No. 2 Voltage ............................ 100 V
Grid No. 1 Voltage ............................ -9 V
Grid No. 1 Voltage Derived from
Cathode Bias Resistor ...................... 1100 Ω
Amplification Factor .......................... 120
Plate Resistance (approx) ..................... 140K Ω
Transconductance .............................. 875 µMho
Plate Current ................................. 7 mA
Grid No. 2 Current ............................ 1.2 mA
Load Resistance ............................... 15K Ω
Power Output (approx) ......................... 0.27 W
Total Harmonic Distortion ..................... 8 %

Class A Amplifier
Source ........................................ RCA RC-13 - 1937
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 ...................... 1100 Ω
Amplification Factor .......................... 120
Plate Resistance (approx) ..................... 130K Ω
Transconductance .............................. 925 µMho
Plate Current ................................. 9 mA
Grid No. 2 Current ............................ 1.5 mA
Load Resistance ............................... 13.5K Ω
Power Output (approx) ......................... 0.55 W
Total Harmonic Distortion ..................... 10 %

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 ...................... 1100 Ω
Amplification Factor .......................... 120
Plate Resistance (approx) ..................... 115K Ω
Transconductance .............................. 1050 µMho
Plate Current ................................. 14 mA
Grid No. 2 Current ............................ 2.4 mA
Load Resistance ............................... 11.6K Ω
Power Output (approx) ......................... 1.0 W
Total Harmonic Distortion ..................... 8 %

Class A Amplifier
Source ........................................ RCA RC-13 - 1937
Plate Voltage ................................. 250 V
Grid No. 2 Voltage ............................ 250 V
Grid No. 1 Voltage ............................ -25 V
Grid No. 1 Voltage Derived from
Cathode Bias Resistor ...................... 970 Ω
Amplification Factor .......................... 120
Plate Resistance (approx) ..................... 100K Ω
Transconductance .............................. 1200 µMho
Plate Current ................................. 22 mA
Grid No. 2 Current ............................ 3.8 mA
Load Resistance ............................... 10K Ω
Power Output (approx) ......................... 2.5 W
Total Harmonic Distortion ..................... 8 %

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Sun, 05 Feb 2023 19:32:59 -0700