12SH7

Sharp-cutoff RF pentode designed for Class A RF and IF amplifier service. Its abrupt cutoff characteristic suits fixed-gain receiver signal stages rather than automatic-gain-controlled variable-mu operation.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: 8BK
Socket code: -
Base pins: 8
Nominal heater: 12.6 V / 150 mA

Description

Sharp-cutoff RF pentode for Class-A RF/IF amplifier service.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 8BK
Socket code: -
Base pins: 8
Nominal heater voltage: 12.6 V
Nominal heater current: 150 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

8BK - Terminal pinout

Electrical assignments shared by every tube using this base designation.

Terminal	Section	Connection	Evidence
PIN1SH	A	SH — Internal Shield EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN2H	—	H — Heater EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN3G3	A	G3 — Suppressor GridGroup 8BK3 EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN3K	A	K — CathodeGroup 8BK3 EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN4G1	A	G1 — Control Grid EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN5G3	A	G3 — Suppressor GridGroup 8BK5 EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN5K	A	K — CathodeGroup 8BK5 EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN6G2	A	G2 — Screen Grid EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN7H	—	H — Heater EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK
PIN8P	A	P — Plate (Anode) EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 129, 8BK

Section ratings

1 physical section, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances

Plate resistance: 900000 Ω
Transconductance: 0.0049 S
Max plate voltage: 300 V
Max screen voltage: 150 V

Promoted from printed maximum/characteristic columns; additional published values retained in TUBE_SECTION_PARAMETER.

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

Pentode

Capacitance

Input capacitance
8.5 pF
Section1
Output capacitance
7 pF
Section1
Grid-to-plate capacitance
0.003 pF
Section1

Other

Plate voltage
250 V
ClassA
Screen voltage
150 V
ClassA
Control-grid voltage
-1 V
ClassA
Plate current
10.8 mA
ClassA
Screen current
4.1 mA
ClassA

Characteristic

Plate resistance
900000 Ω
Section1
Transconductance
4900 µS
Section1