Data set 01
1950 Sylvania
Published operating points and test conditions from this source.
SECTION 1
Pentode
Characteristic
Transconductance
5000 µS
Other
Maximum Plate Voltage
180 V
Plate Voltage
120 V
Voltage Pentode - Sharp Cutoff (single) ·Pentode
408A
Western Electric miniature sharp-cutoff RF pentode developed for reliable communications and high-frequency amplifier service.
Directly heatedCold cathodeCommon cathodeDissimilar
- Sections
- 1
- Base
- 76D
- Socket code
- B7G
- Base pins
- 7
- Nominal heater
- 20 V / 50 mA
Description
Miniature sharp-cutoff RF pentode designed for reliable communications service.
Socket description
Miniature 7-contact
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- 76D
- Socket code
- B7G
- Base pins
- 7
- Nominal heater voltage
- 20 V
- Nominal heater current
- 50 mA
- Parallel heater voltage
- -
- Parallel heater current
- -
- Series capable
- No
76D - Terminal pinout
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
Section ratings
1 physical section, each with unique specifications.
Section 1
Pentode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 300000 Ω
- Transconductance
- 0.005 S
- Max plate voltage
- 180 V
- Max screen voltage
- 140 V
- Max plate dissipation
- 1.7 W
- Max screen dissipation
- 0.5 W
- Max cathode current
- 12 mA
Promoted fields mapped from printed maximum-rating and characteristic headings; additional published values preserved in parameter rows.
Source-dependent data
Operating conditions by source
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.
Data set 02
1965 Ericsson Longlife
Published operating points and test conditions from this source.
SECTION 1
Pentode
Other
Plate supply voltage
120 V
ClassA
Screen-grid supply voltage
120 V
ClassA
Cathode bias resistor
200 Ohm
ClassA
Zero-signal plate current
7.5 mA
ClassA
Maximum-signal plate current
7.7 mA
ClassA
Zero-signal screen-grid current
1.9 mA
ClassA
Maximum-signal screen-grid current
2.7 mA
ClassA
Load resistance
15000 Ohm
ClassA
Power output
0.325 W
ClassA
Total harmonic distortion
12 %
ClassA
Transconductance minimum
3900 uS
Transconductance maximum
6000 uS
Characteristics
Transconductance
5000 uS
ClassA
Plate resistance
0.3 MOhm
ClassA
Screen-to-control-grid amplification factor
24 ratio
ClassA
Data set 03
1971 RCA HB3 Binder 3 of 7
Published operating points and test conditions from this source.
SECTION 1
Pentode
Other
Maximum plate voltage
- to 180 V
Maximum screen voltage
- to 180 V
Maximum plate dissipation
- to 1.7 W
Maximum screen dissipation
- to 0.5 W
Characteristics
Plate resistance
340000 Ω
Transconductance
5000 µS
Plate supply voltage
120 V
ClassA
Grid No.2 supply voltage
120 V
ClassA
Cathode resistor
200 Ω
ClassA
Plate resistance
340000 Ω
ClassA
Transconductance
5000 µS
ClassA
Plate current
7 mA
ClassA
Grid No.2 current
2.2 mA
ClassA
Data set 04
2026 Western Electric 400s
Published operating points and test conditions from this source.
SECTION 1
Pentode
Characteristic
Plate Current ., , Eb = Eg
120 milliamperes
Plate Current ., , Eb = Eg2 ~ 120 volis; . 7.5 milliamperes
Transconductance . Cathode-Bias Resistor =
200 micromhos
Transconductance . Cathode-Bias Resistor = 200 chms { 5000 micromhos
Heafer Voltage, A-C or D-C . . . . . & . &« v v o v « «
20 volts
Heafer Voltage, A-C or D-C . . . . . & . &« v v o v « « . 20 volts
Cathode Current ., . . « & & & v v
4 milliamperes
Cathode Current ., . . « & & & v v 4 4 4 v o 4 e e v a 12 milliamperes
Heater-Cathkode Voltagel e e e e e e e e e e e e e e
120 volts
Heater-Cathkode Voltagel e e e e e e e e e e e e e e 120 volts
Transconductance . « o o o o = + « s o ¢ » o <
5000 micromhos
Transconductance . « o o o o = + « s o ¢ » o < 5000 5600 micromhos
Load Resistance . . . « . v ¢ ¢« « = & o s s =«
15000 ohms
Load Resistance . . . « . v ¢ ¢« « = & o s s =« 15000 15C00 ohms
Total Harmonis Distortion . + - + o « o s o <
12 per cent
Total Harmonis Distortion . + - + o « o s o < 12 5.5 per cent
Plcte Current of
10 volts
Plcte Current of 10 Microampares . . . . « - -6.8 -6.8 volts
voltage should not exceed
90 volts
voltage should not exceed 90 volts.
SCREEN GRID VOLTAGE=
120 VOLTS
SCREEN GRID VOLTAGE=120 VOLTS
|SCREEN GRID VOLTAGE=
120 VOLTS
- |SCREEN GRID VOLTAGE=120 VOLTS
Other
Plate Dissipation . . & . v v v ¢ o v
4 watts
Plate Dissipation . . & . v v v ¢ o v 4 @ ¢ 4 e e e e 1.7 watts