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Tube Substitutions for:
4BQ7A
Medium-Mu High Frequency Twin Triode
TypeSubstitutesBase Diagram
4BQ7A4BC8, 4BZ7, 4BZ8, 4KN8, 4BS8, 4BX8, 5BK7A
Web References4BQ7A (RCA (HB3)) @ Franks Electron Tubes
4BQ7A (General Electric) @ Franks Electron Tubes
4BQ7A (Tung-Sol) @ Franks Electron Tubes
4BQ7A (RCA (RC30)) @ Franks Electron Tubes
4BQ7A @ RadioMuseum.org
Sylvania Type 4BQ7A
VHF DUO TRIODE



MECHANICAL DATA

Bulb T-61/2
Base Small Button 9-Pin
Basing 9AJ
Mounting Position Any


ELECTRICAL DATA


HEATER CHARACTERISTICS
Heater Voltage 4.2 Volts
Heater Current 600 Ma
Heater Warm-up Time 11 Seconds
Maximum Peak Heater-Cathode Voltage 200 Volts

DIRECT INTERELECTRODE CAPACITIES (Shielded)1
Grid to Plate 1.2 1.2 ��f
Input 2.6   ��f
Output 1.2   ��f
Plate to Cathode 0.12 0.12 ��f
Heater to Cathode 2.6 2.6 ��f
Plate to Plate 0.010 0.010 ��f
Plate Section 2 Plate and Grid Section 1 0.024 0.024 ��f
Grounded Grid Operation
Input 5.0 ��f
Output 2.2 ��f

MAXIMUM RATINGS (Design Center Values) Each Section
Plate Voltage 250 Volts
Plate Dissipation 2 Watts
Cathode Current 20 Ma
Grid Circuit Resistance 0.5 Megohm

CHARACTERISTICS AND TYPICAL OPERATION
CLASS A1 AMPLIFIER (Each Section)
Plate Voltage 150 Volts
Cathode Bias Resistor 220 Ohms
Plate Current 9 Ma
Transconductance 6400 �mhos
Amplification Factor 38 X
Grid Voltage for Ib=100�a (approx.) -6.5 Volts
Direct Coupled R F Grounded Grid Operation4
  Section 1 Section 2  
Plate Supply Voltage 250 250 Volts
Plate Voltage 135 115 Volts
Negative Grid Voltage -1   Volts
Cathode Bias Resistor 100   Ohms
Grid Resistor   0.5 Megohm
Plate Current 10 10 Ma
Grid Current 0 0 Ma
Grid Voltage for Ib=10�a (approx.) -14   Volts
Push-Pull R F Grounded Grid Operation
Plate Voltage 150 Volts
Grid Voltage -2 Volts
Cathode Bias Resistor (Common to both sections) 100 Ohms
Plate Current 10 Ma

NOTES:

1 RETMA shield No. 315
2 Section No. 1 connects to Pins 6, 7 and 8. Section No. 2 connects to Pins 1, 2 and 3.
3 Under cutoff conditions, in r f grounded grid circuits with direct coupled drive, this voltage may be as high as 300 volts.
4 Section No. 1 (Driver) is directly coupled to Section No. 2 (Driven Grounded Grid Amplifier)

APPLICATION

Sylvania Type 4BQ7A is a miniature, medium mu, twin triode intended for service as the first amplifier in tuners or v h f television receivers or other applications require a high gain, low noise twin triode amplifier.



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