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Tube Substitutions for:
6F7
Low Mu Triode - Remote Cutoff Pentode

Type	Substitutes	Base Diagram
6F7	6F7S
Web References	6F7 (Sylvania) @ Franks Electron Tubes 6F7 (Tung-Sol) @ Franks Electron Tubes 6F7 @ RadioMuseum.org

Cunningham Type 6F7
TRIODE - REMOTE CUTOFF RF PENTODE


MECHANICAL DATA

Bulb	ST-12
Base	Small 7 Pin
Basing	7E
Cap	Small Metal

ELECTRICAL DATA

HEATER CHARACTERISTICS

Heater Voltage	6.3	Volts
Heater Current	0.3	Amps

DIRECT INTERELECTRODE CAPACITANCES
Triode Unit

Grid to Plate	2.0	��f
Grid to Cathode	2.5	��f
Plate to Cathode	3.0	��f

Pentode Unit

Grid to Plate (With shield-can)	0.008	��f
Input	2.3	��f
Output	12.5	��f

MAXIMUM RATINGS
Triode Unit

Plate Voltage	100	Volts
Grid Voltage	-3	Volts
Amplification Factor	8	X
Plate Resistance	17800	Ohms
Mutual Conductance	450	�mhos
Plate Current	3.5	Ma

Pentode Unit

Plate Voltage	250	Volts
Screen Voltage	100	Volts
Grid Voltage	-3	Volts
Amplification Factor	900	X
Plate Resistance	850000	Ohms
Mutual Conductance	1100	�mhos
Mutual Conductance (At -35 volts bias)	10	�mhos
Plate Current	6.5	Ma
Screen Current	1.5	Ma

TYPICAL OPERATION
Frequency Converter

	triode	pentode
Plate Voltage	1001	250	Volts
Screen Voltage	-	100	Volts
Grid Bias Voltage	3	-102	Volts
Oscillator Peak Voltage Output	-	7	Volts
D-C Grid Current	0.15	0	Ma
D-C Plate Current4	3.5	6.5	Ma
Screen Current	-	0.6	Ma
Plate Resistance	-	2.0	Megohm
Conversion Transconductance	-	300	�mhos

NOTES:

1	May be obtained from 250-volt source through 60000-ohm dropping resistor.
2	Obtained by means of 1700-ohm self-biasing (cathode) resistor.
3	Obtained by 100000-ohm grid-leak resistor retured directly to cathode.
4	Oscillator conditions should be adjusted so that plate current does not exceed maximum of 4 Ma.

INSTALLATION
The base pins of the 6F7 fit the seven-contact (0.75 inch pin-circle diameter) socket which may be installed to hold the tube in any position.
The heater of the 6F7 is designed to operate on either d.c. or a.c. For operation on a.c. with a transformer, the winding which supplies the heater circuit should operate the heater at its recommended value for full-load operating conditions at average line voltage. For service in automobile receivers, the heater terminals of the 6F7 socket should be connected directly across a 6-volt battery. In receivers that employ a series-heater connection, the heater of the 6F7 may be operated in series with the heater of other types having a 0.3 ampere rating. The current in the heater circuit should be adjusted to 0.3 ampere for the normal supply line voltage.
The cathode of the 6F7, when operated from a transformer, should preferably be connected directly to the electrical mid-point of the heater circuit. When it is operated in receivers employing a 6-volt storage battery for the heater supply, the cathode circuit is tied in either directly or thourgh biasing resistors to the negative battery terminal. In "transformerless" receivers with a series-heater circuit, the cathode circuit of the 6F7 is tied in either directly or through biasing resistors to the negative side of the d-c plate supply which is furnished either by d-c power line or by the a-c line by means of a rectifier. In circuits where the cathode is not directly connected to the heater, the potential difference between them should be ketp as low as possible. If the use of a large resistor is necessary between the heater and cathod of the 6F7 in some circuit designs, it should be by-passed by a suitable filter network or objectionable hum may develop.
Complete shielding of the 6F7 is generally necessary to prevent intercoupling between its circuit and the circuits of other stages.

APPLICATION
Being of the multi-unit type, the 6F7 is suitable for diversified applications. The triode unit and the pentode unit can be utilized independently of each other for performing any of the functions expected of single-unit types with similar characteristics. Circuit design for the 6F7, therfore, will follow conventional practice.
As a frequency converter, the 6F7 is used by employing the triode unit as oscillator and the pentode unit as mixer (first detector). The circuit should be adjusted so that the grid-bias voltage is approximately 3 volts greater than the peak oscillator voltage. In opreation, the plate current of the oscillator should not exceed 4 Ma.


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