NJ7P SQL Tube Database Query

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57
Sharp-Cutoff Pentode

EIA Base & Outline

EIA Base: 6FEIA Bulb: 12-2

Substitute Data

Substitutes ................................... 58
Source ........................................ RCA R-10 - 1932

Application

Source ........................................ RCA R-10 - 1932
The 57 is a triple-grid tube recommended especially for service as a biased detector in a-c receivers designed for its characteristics. In s such service, this tube is capable of delivering a large audio-frequency output voltage with relatively small input voltage. Other applications of the 57 include its use as a low signal-input, screen grid amplifier tube and as an automatic volume control tube. The 57 is characterized by the small overall size, the dome-top bulb, the internal shield in the dome, the rigidity of electrode assembly, and the fifth electrode or suppressor with its own base pin terminal. Equally significant among its electrical features are its relatively low heater power consumption, its sharp plate current cut-off with respect to grid voltage, and its adaptability of electrode combinations to unusual circuit applications.

The internal shield is a distinctive feature in the design of this tube. It is placed in the bulb dome above the electrode assembly and is connected within the tube directly to the cathode. The dome-top bulb makes possible close proximity of the external and internal shields and, therefore, a low effective grid-plate capacitance. The form of the external shield-can may be somewhat modified depending upon the receiver design requirements for minimum grid-plate and output capacitance.

Mechanical Data

Source ........................................ RCA R-10 - 1932
Bulb .......................................... ST-12
Base Type ..................................... Small 6-Pin
EIA Outline ................................... 12-2
EIA Base ...................................... 6F
Top Cap ....................................... Small Metal
Mounting Position ............................. Any

Electrical Data

Source ........................................ RCA R-10 - 1932
Heater Voltage ................................ 2.5 V
Heater Current ................................ 1.0 A

Direct Interelectrode Capacitances (approx)

Pentode
Source ........................................ RCA R-10 - 1932
Input ......................................... 5.2 pf
Output ........................................ 6.8 pf
Grid to Plate ................................. 0.010 pf

Pentode
Source ........................................ RCA RC-13 - 1937
Input ......................................... 5.0 pf
Output ........................................ 6.5 pf
Grid to Plate ................................. 0.007 pf

Maximum Ratings (Design Center Values)

Pentode
Source ........................................ RCA R-10 - 1932
Plate Voltage ................................. 250 V
Grid No. 2 Voltage ............................ 100 V

Characteristics and Typical Operation

Class A Amplifier
Source ........................................ RCA R-10 - 1932
Plate Voltage ................................. 250 V
Grid No. 2 Voltage ............................ 100 V
Grid No. 1 Voltage ............................ -3.0 V
Amplification Factor .......................... 1500
Plate Resistance (approx) ..................... 1M Ω
Transconductance .............................. 1225 µMho
Plate Current ................................. 2.0 mA
Grid No. 2 Current ............................ 1.0 mA

Source ........................................ RCA RC-13 - 1937
For other characteristics and typical operation, see 6J7

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Thu, 30 Jun 2022 07:28:35 -0700