28D7

Double beam-power amplifier with a 28-volt heater, providing two power sections for output-amplifier applications according to the supplied receiving-tube handbook.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: 8BS
Socket code: -
Base pins: 8
Nominal heater: 28 V / 400 mA

Description

28D7 is listed in the supplied receiving-tube handbook as a double beam-power amplifier. The published heater/filament rating is 28.0 V at 0.4 A. Maximum ratings and representative operating characteristics were transcribed from the supplied table.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 8BS
Socket code: -
Base pins: 8
Nominal heater voltage: 28 V
Nominal heater current: 400 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

8BS - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

2 physical sections, each with unique specifications.

Section 1

Beam Power

X-ray radiationInterelectrode capacitances

Plate resistance: 4200 Ω
Transconductance: 0.0034 S
Max plate voltage: 100 V
Max screen voltage: 67.5 V

Published maximum ratings, representative operating conditions, rectifier service data, and capacitance columns reviewed.

Section 2

Beam Power

X-ray radiationInterelectrode capacitances

Plate resistance: 4200 Ω
Transconductance: 0.0034 S
Max plate voltage: 100 V
Max screen voltage: 67.5 V

Identical second physical BeamPower section; duplicated from representative section per physical-section-row policy.

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 01

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Beam Power

Other

Maximum plate voltage
100 V
Published handbook rating
Maximum screen voltage
67.5 V
Published handbook rating
Plate voltage
28 V
ClassA
Screen voltage
28 V
ClassA
Control-grid bias
3.5 V
ClassA
Plate current
12.5 mA
ClassA
Screen current
1 mA
ClassA
Load resistance
4000 ohm
ClassA
Power output
0.1 W
ClassA

Characteristic

Plate resistance
4200 ohm
Published handbook characteristic
Transconductance
3400 µS
Published handbook characteristic
Heater/filament voltage
28 V
Published heater/filament rating
Heater/filament current
400 mA
Published heater/filament rating