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Tube Substitutions for:
KT77

TypeSubstitutesBase Diagram
KT776CA7
Web ReferencesKT77 (GEC) @ Franks Electron Tubes
KT77 (M-O Valve) @ Franks Electron Tubes
KT77 (JJ) @ Franks Electron Tubes
GEC Type KT77
BEAM POWER AMPLIFIER


Bulb Special, straight
Base Metal Octal 8-Pin
Basing 8ET
Cathode Coated Unipotential
Mounting Position Vertical preferred.


ELECTRICAL DATA


FILAMENT CHARACTERISTICS
Filament Voltage (AC) 5.0 Volts
Filament Current 1.5 Amps

DIRECT INTERELECTRODE CAPACITIES
Grid No. 1 to Plate 1.0 ��f
Input 15.5 ��f
Output 7.2 ��f

MAXIMUM RATINGS
Triode Operation Connected
Plate Voltage 500 Volts
Plate Dissipation 30 Watts
Grid No. 1 Cathode Bias Resistance 0.71 Megohm
Pentode Connected
Plate Voltage 800 Volts
Grid No. 2 Voltage 425 Volts
Plate Dissipation 25 Watts
Grid No. 2 Dissipation 8.0 Watts
Cathode Current 150 Ma
Grid No. 1 Cathode Bias Resistance 0.72 Megohm

CHARACTERISTICS AND TYPICAL OPERATION
Triode Operation Push-Pull
Plate Voltage 400 Volts
Cathode Resistor 220 Ohms
Zero Signal Plate Current 130 Ma
Max. Signal Plate Current 142 Ma
Load Resistance 5000 Ohms
Power Output 16.5 Watts
Total Harmonic Distortion 3 Percent
Pentode Operation Single Tube
Plate Voltage 265 300 Volts
Grid No. 2 Voltage 250 300 Volts
Cathode Resistor   190 Ohms
Grid No. 1 Voltage -13.5   Volts
Zero Signal Plate Current 100 83 Ma
Transconductance 11000 11000 �mhos
Plate Resistance 2000 3500 Ohms
Power Output 11 11 Watts
Total Harmonic Distortion 10 10 Percent
Class AB1 Push-pull (Pentode Operation)
Plate Voltage 375 450 400 Volts
Grid No. 2 Voltage 375 450 400 Volts
Grid NO. 2 Resistor 470 1000 800 Ohms
Grid No. 1 Voltage     -36 Volts
Cathode Resistor 130 232   Ohms
A-F Grid Voltage (RMS) 20 27 25 Volts
Zero Signal Plate Current 150 120 60 Ma
Max. Signal Plate Current 188 143 221 Ma
Zero Signal Grid No. 2 Current 25 20 9 Ma
Max. Signal Grid NO. 2 Current 39 44 46 Ma
Load Resistance (P to P) 3500 6500 3500 Ohms
Power Output 35 40 54 Watts
Total Harmonic Distortion 1.7 5.1 1.6 Percent
Class AB1 Push-pull (Ultra-Linear Operation)
Plate Voltage 430 430 Volts
Cathode Resistor 235 235 Ohms
A-F Grid Voltage (RMS) 17.5 25 Volts
Zero Signal Plate Current 125 125 Ma
Max. Signal Plate Current 130 140 Ma
Zero Signal Grid No. 2 Current 20 20 Ma
Max. Signal Grid NO. 2 Current 20.4 28 Ma
Load Resistance (P to P) 6000 6000 Ohms
Power Output 20 34 Watts
Total Harmonic Distortion 0.35 2.5 Percent

NOTES:

1 The maximum permissible limit for Grid No. 1 Resistor in a Class B Circuit is 0.5 Megohms.
2 Grid No. 2 at 43% of Primary Winding.

APPLICATION

Type KT77 is a beam power audio amplifier capable of producing 100 watts of output power. This typ has found extensive use in applications requiring extremely high power outputs.



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