(RCA HB-3 data courtesy Paul Bigelow and John Shriver)
RCA JAN 3, 1955
26A7-GT TWIN BEAM POWER TUBE
GENERAL DATA
Electrical:
Heater, for Unipotential Cathode:
Voltage.............. 26.5 ac or dc volts
Current.............. 0.6 amp
Direct interelectrode Capacitance:(1)
Grid #1 to plate(2) 1.2 uuf
Grid #1 to cathode & grid #3,
grid #2 and heater(2) 16 uuf
Plate to cathode & grid #3,
grid #2 and heater(2) 13 uuf
Grid #1 of unit #1 to
grid #1 of unit #2 0.2 uuf
Plate of unit #1 to
plate of unit #2 0.2 uuf
Grid #1 of unit #1 to
plate of unit #2 0.2 uuf
Grid #1 of unit #2 to
plate of unit #1 0.2 uuf
(1) without external shield
(2) each unit
Mechanical:
Mounting Position............. Any
Maximum Overall Length 3-13/16"
Maximum Seated Length 3-1/4"
Maximum Diameter 1-9/32"
Bulb T-9
Base: Intermediate-Shell Octal 8-pin (JETEC No. B8-6)
Short Intermediate Shell Octal 8-pin (JETEC No. B8-58)
Basing Designation for BOTTOM VIEW........8BU
Pin Electrode
1 Grid #1, Unit #1
2 Cathode & Grid #3 of Units #1 and #2
3 Grid #1, Unit #2
4 Plate of Unit #2
5 Grid #2 of Units #1 and #2
6 Heater
7 Heater
8 Plate of Unit #1
AMPLIFIER - Class A1
Values are for each unit
Maximum Ratings, Design-Center Values:
PLATE VOLTAGE.......................... 50 max volts
GRIDS No. 2. (SCREEN) VOLTAGE.......... 50 max volts
PLATE DISSIPATION...................... 2 max watts
GRIDS No. 2 Input...................... 0.5 max watt
PEAK HEATER-CATHODE VOLTAGE:
Heater negative w.r.t cathode....... 90 max volts
Heater positive w.r.t cathode....... 90 max volts
Typical Operation and Characteristics (Each Unit):
=====================================================
Plate Voltage 26.5 volts
Grid #2 Voltage 26.5 volts
Grid #1 (control grid) Voltage -4.5 volts
Peak AF Grid #1 Voltage 4.5 volts
Zero-Signal Plate Current 20 ma
Max-Signal Plate Current 20.5 ma
Zero-Signal Grid #2 Current 1.9 ma
Max-Signal Grid #2 Current 5.5 ma
Transconductance 5700 umhos
Load Resistance 1500 ohms
Total Harmonic Distortion 7 %
Max-Signal Output Power 180 mw
Maximum Circuit Values:
=======================================================
Grid #1 Circuit Resistance:
For maximum rated conditions:
With cathode bias............. 0.5 max megohm
With fixed bias............... 0.1 max megohm
For conditions where the maximum
design values of plate voltage and
grid #2 voltage do not exceed 26.5 Volts:
With grid-resistor bias....... 0.5 max megohm
AF POWER AMPLIFIER -- Class AB1
Unless otherwise specified, values are on a per tube basis
Maximum Ratings, Design-Center Values:
PLATE VOLTAGE.......................... 50 max volts
GRIDS No. 2. (SCREEN) VOLTAGE.......... 50 max volts
PLATE DISSIPATION (per unit)........... 2 max watts
GRIDS No. 2 Input (per unit)........... 0.5 max watt
PEAK HEATER-CATHODE VOLTAGE:
Heater negative w.r.t cathode....... 90 max volts
Heater positive w.r.t cathode....... 90 max volts
Typical Push-Pull Operation:
Plate Voltage.......................... 26.5 volts
Grid #2 Voltage 26.5 volts
Grid #1 (control grid) Voltage -7 volts
Peak AF Grid #1 to Grid #1 Voltage 14 volts
Zero-Signal Plate Current 19 ma
Max-Signal Plate Current 30 ma
Zero-Signal Grid #2 Current (approx) 2 ma
Max-Signal Grid #2 Current (approx) 8.5 ma
Effective Load Resistance
plate to plate 2500 ohms
Total Harmonic Distortion 5 %
Max-Signal Power Output 500 mw
Maximum Circiut Values:
Grid #1 Circuit Resistance for
maximum rated conditions:
With cathode bias 0.5 max megohm
With fixed bias 0.1 max megohm
For conditions where the maximum
design values of plate voltage and
grid #2 voltage do not exceed 26.5 volts:
With grid-resistor bias 0.5 max megohm
Average Plate Characteristics Pentode Connection
Average Plate Characteristics Triode Connection
Operation Characteristics Push-Pull Circuit
