Data set 01
1961 Tung Sol
Published operating points and test conditions from this source.
SECTION 1
Triode
Other
Heater voltage
12.6 V
Nominal
Heater current
300 mA
Nominal
Plate voltage
300450 V
Typical operating conditions
Voltage - Dual Triode (similar) ·Triode-Triode
12BH7A
Medium-mu twin triode capable of substantially greater current than small-signal high-mu types, used for amplifier, driver, and television deflection service.
Directly heatedCold cathodeCommon cathodeDissimilar
- Sections
- 2
- Base
- 9A
- Socket code
- B9A
- Base pins
- 9
- Nominal heater
- 12.6 V / 300 mA
Description
12BH7A — Medium-Mu Twin Triode Vacuum Tube
An indirectly heated, dual-section miniature valve designed for television deflection circuits, oscillators, phase inverters, and multivibrator applications.
Overview
The 12BH7A (also designated as 12BH7-A) is a miniature, medium-mu twin triode containing two independent, high-perveance triode units within a single T-6 1/2 glass envelope. Each triode section is electrically independent except for a shared heater. The tube is designed with a 9-pin miniature button base (Noval) and is highly optimized for television receiver applications.
The primary applications of the 12BH7A include serving as a combined vertical-deflection sweep generator and deflection amplifier, or as a horizontal-deflection oscillator in television receivers. It is also widely utilized in phase-inverter and multivibrator circuits, as well as general-purpose radio frequency (R.F.) and low-frequency amplification.
A key feature of the 12BH7A is its controlled heater warm-up characteristic, which minimizes heater voltage surges when the tube is operated in series-string heater arrangements with other 600 mA television receiver tubes. This controlled warm-up, along with a controlled cutoff rating, distinguishes the 12BH7A from its predecessor, the standard 12BH7, which is otherwise identical.
Construction, Physical Dimensions, and Base
The 12BH7A is constructed with two separate, coated unipotential cathodes. The tube is housed in a T-6 1/2 glass bulb with a small-button 9-pin Noval base (JETEC E9-1). It can be mounted in any physical position.
Physical Dimensions
- Maximum Diameter: 0.815 to 0.875 inches (22.0 mm)
- Maximum Seated Length: 2.375 inches (51.2 mm)
- Maximum Overall Length: 2.625 inches (57.6 mm)
- Length from Base Seat to Bulb Top (excluding tip): 2 inches 3/32 inches
Pinout and Terminal Connections
The tube utilizes the 9A (or JEDEC 9A) basing arrangement. The terminal connections, viewed from the bottom of the base, are assigned as follows:
| Pin | Connection |
|---|---|
| 1 | Plate (Triode Unit 2) |
| 2 | Grid (Triode Unit 2) |
| 3 | Cathode (Triode Unit 2) |
| 4 | Heater (Triode Unit 2) |
| 5 | Heater (Triode Unit 1) |
| 6 | Plate (Triode Unit 1) |
| 7 | Grid (Triode Unit 1) |
| 8 | Cathode (Triode Unit 1) |
| 9 | Heater Mid-Tap |
Heater Characteristics and Warm-Up Control
The heater of the 12BH7A is designed for flexible operation, allowing for either series or parallel connection depending on the circuit requirements.
| Heater Parameter | Series Connection | Parallel Connection |
|---|---|---|
| Heater Voltage (AC/DC) | 12.6 V | 6.3 V |
| Heater Current | 0.3 A (300 mA) | 0.6 A (600 mA) |
| Heater Supply Limits (Voltage) | 12.6 V 1.3 V | 6.3 V 0.6 V |
| Heater Supply Limits (Current) | 300 mA 20 mA | 600 mA 40 mA |
| Average Warm-up Time | 11 seconds | 11 seconds |
Heater Power Calculation
Using the nominal voltage and current ratings, the heater power consumption is calculated as:
- Series: 12.6 V * 0.3 A = 3.78 W
- Parallel: 6.3 V * 0.6 A = 3.78 W
Heater Warm-Up Time Measurement
The controlled heater warm-up time is verified using a standardized test circuit. The warm-up time is defined as the time required for the voltage across the heater terminals to rise from zero to a specified test voltage (V1) under the following conditions:
- Applied Voltage (E): 25.0 V (RMS or DC)
- Total Series Resistance (R): 31.5 Ohms
- Heater Test Voltage (V1): 5.0 V (RMS or DC)
- Rated Heater Voltage (Ef): 6.3 V
- Rated Heater Current (If): 0.6 A
Heater-Cathode Voltage Ratings
To prevent insulation breakdown between the heater and the cathodes, the following maximum design-center voltage limits must be observed:
- Heater Negative with Respect to Cathode: 200 V max (DC and Peak combined)
- Heater Positive with Respect to Cathode: 100 V max (DC component), 200 V max (DC and Peak combined)
Electrical Characteristics and Class A1 Operation
Under typical Class A1 amplifier operating conditions for each triode unit, the 12BH7A exhibits the following electrical characteristics:
- Plate Voltage: 250 V
- Grid Voltage: -10.5 V (some older references list -14 V for a plate current of 4.0 mA)
- Amplification Factor (μ): 16.5 to 17
- Plate Resistance (rp): 5300 to 5500 Ohms (approximate)
- Transconductance (gm): 3100 μmhos (micromhos)
- Plate Current: 11.5 mA
- Grid Voltage for Cutoff:
- Approximately -23 V for a plate current of 50 μs (at 250 V plate voltage)
- Approximately -17 V for a plate current of 50 μs (at 150 V plate voltage)
- Approximately -25 V for a plate current of 10 μs (at 250 V plate voltage)
Class A1 Amplifier Maximum Ratings (Design-Center Values)
- Plate Voltage: 300 V max
- Negative DC Grid Voltage: 50 V max
- Positive DC Grid Voltage: 0 V max
- Cathode Current: 20 mA max
- Plate Dissipation (Each Plate): 3.5 W max
- Plate Dissipation (Both Plates Operating): 7.0 W max
- Grid-Circuit Resistance (Fixed Bias): 0.25 MOhm max
- Grid-Circuit Resistance (Cathode Bias): 1.0 MOhm max
Television Deflection and Oscillator Service
The 12BH7A is highly specialized for television sweep circuits. Its ratings are divided into specific categories based on the scanning system requirements (typically a 525-line, 30-frame system).
Comparative Service Ratings (Design-Center Values)
| Parameter | Vertical Deflection Amplifier | Vertical Deflection Oscillator | Horizontal Deflection Oscillator |
|---|---|---|---|
| DC Plate Voltage (Max) | 450 to 500 V | 450 V | 450 V |
| Peak Positive-Pulse Plate Voltage | 1350 to 1500 V (Abs. Max) | — | — |
| Peak Negative-Pulse Grid Voltage (Max) | 200 to 250 V | 400 V | 600 V |
| DC Grid Voltage (Max) | -50 V | — | — |
| Peak Cathode Current (Max) | 70 mA | 70 mA | 300 mA |
| Average Cathode Current (Max) | 20 mA | 20 mA | 20 mA |
| Plate Dissipation (Each Plate, Max) | 3.5 W | 3.5 W | 3.5 W |
| Plate Dissipation (Both Plates, Max) | 7.0 W | 7.0 W | 7.0 W |
| Grid-Circuit Resistance (Max) | 2.2 to 2.5 MOhm (Cathode Bias) | 2.2 MOhm (Fixed/Cathode Bias) | 2.2 MOhm (Fixed/Cathode Bias) |
Pulse Duration and Duty Cycle Constraints
For both vertical and horizontal deflection services, the peak pulse ratings are strictly constrained by duty cycle limits:
- Vertical Deflection: The pulse duration must not exceed 15% of one vertical scanning cycle, which equates to 2.5 milliseconds in a 525-line, 30-frame system.
- Horizontal Deflection: The pulse duration must not exceed 15% of one horizontal scanning cycle, which equates to 10 microseconds in a 525-line, 30-frame system.
Circuit Protection Requirements
When operating the 12BH7A in stages utilizing grid-leak bias, an adequate cathode-bias resistor or other protective means must be incorporated. This safeguard protects the triode units from excessive current and subsequent damage in the event of an excitation failure or loss of drive signal.
Interelectrode Capacitances
The direct interelectrode capacitances of the 12BH7A vary depending on whether an external shield is utilized. The following values represent typical measurements for each triode unit:
| Capacitance Parameter | With Shield (Shield #315)* | Without Shield |
|---|---|---|
| Grid to Plate (Each Unit) | 2.4 pF | 2.6 pF |
| Input: Grid to (Heater + Cathode) | 3.3 pF | 3.2 pF |
| Output Unit 1: Plate to (Heater + Cathode) | 2.0 pF | 0.5 pF |
| Output Unit 2: Plate to (Heater + Cathode) | 2.0 pF | 0.4 pF |
| Coupling: Plate of Unit 1 to Plate of Unit 2 | 0.6 pF | 0.8 pF |
Note: Shield #315 is connected to the cathode of the unit under test.
Technical Summary
The 12BH7A is a versatile, high-perveance, medium-mu twin triode housed in a 9-pin miniature Noval envelope. It features a dual-voltage heater (12.6 V series / 6.3 V parallel) with a controlled warm-up time of approximately 11 seconds, making it ideal for series-string television receivers. At a typical operating point of 250 V plate voltage and -10.5 V grid bias, each section provides an amplification factor of 16.5 to 17, a transconductance of 3100 μmhos, and a plate resistance of 5300 to 5500 Ohms.
Designed primarily for demanding television deflection applications, the 12BH7A handles high peak positive plate pulses up to 1500 V in vertical deflection amplifier service and peak cathode currents up to 300 mA in horizontal deflection oscillator service. Its independent triode sections, robust pulse capability, and controlled cutoff characteristics make it a highly reliable component for television sweep generators, oscillators, multivibrators, and general-purpose amplifiers.
Socket description
Small-button Noval 9-contact
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- 9A
- Socket code
- B9A
- Base pins
- 9
- Nominal heater voltage
- 12.6 V
- Nominal heater current
- 300 mA
- Parallel heater voltage
- 6.3 V
- Parallel heater current
- 600 mA
- Series capable
- Yes
9A - Terminal pinout
Electrical assignments shared by every tube using this base designation.
| Terminal | Section | Connection | Evidence |
|---|---|---|---|
| PIN12P | B | P — Plate (Anode) EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN22G1 | B | G1 — Control Grid EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN32K | B | K — Cathode EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN4H | — | H — Heater EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN5H | — | H — Heater EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN61P | A | P — Plate (Anode) EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN71G1 | A | G1 — Control Grid EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN81K | A | K — Cathode EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN9HCT | — | HCT — Heater Center Tap EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
Section ratings
2 physical sections, each with unique specifications.
Section 1
Triode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 5300 Ω
- Transconductance
- 0.0031 S
- Amplification factor
- 16.5
- Max plate voltage
- 300 V
- Max plate dissipation
- 3.5 W
- Max cathode current
- 20 mA
Each identical triode; vertical-deflection service.
Section 2
Triode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 5300 Ω
- Transconductance
- 0.0031 S
- Amplification factor
- 16.5
- Max plate voltage
- 300 V
- Max plate dissipation
- 3.5 W
- Max cathode current
- 20 mA
Second physical triode section; electrically identical twin section.
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 Westinghouse Data Book
Published operating points and test conditions from this source.
SECTION 1
Triode
Characteristic
Heater Voltage
12.6 V
Heater Current
300 mA
Plate Current
11.5 mA
Plate Resistance
5500 ohm
Transconductance
3100 uS
Amplification Factor
17
Grid To Plate Capacitance
2.4 pF
Input Capacitance
3.3 pF
Output Capacitance
0.5 pF
Other
Plate Voltage
250 V
EachUnit
Grid Voltage
-10.5 V
EachUnit
Peak Positive Pulse Plate Voltage
1350 V
VerticalDeflection
PeakNegativeGridVoltage
200 V
VerticalDeflection
Data set 03
1966 Tung Sol Electronic Tubes 2 of 4
Published operating points and test conditions from this source.
SECTION 1
Triode
Capacitance
GRID TO PLATE: G TO P
24 pF
Published datasheet; operating column 1
GRID TO PLATE: G TO P
2.6 pF
Published datasheet; operating column 2
INPUT: G TO (H+K)
3.3 pF
Published datasheet; operating column 1
INPUT: G TO (H+K)
3.2 pF
Published datasheet; operating column 2
GRID TO PLATE: G TO P
2.4 pF
Published datasheet; operating column 1
Characteristic
VOLTAGE
6.3 V
Published datasheet; operating column 1
VOLTAGE
12.6 V
Published datasheet; operating column 2
CURRENT
600 mA
Published datasheet; operating column 1
CURRENT
300 mA
Published datasheet; operating column 2
VOLTAGE
0 V
Published datasheet; operating column 1
VOLTAGE
0.6 V
Published datasheet; operating column 3
CURRENT
0 mA
Published datasheet; operating column 1
CURRENT
40 mA
Published datasheet; operating column 3
DC PLATE VOLTAGE
300 V
Published datasheet; operating column 1
DC PLATE VOLTAGE
450 V
Published datasheet; operating column 2
PEAK POSITIVE PULSE PLATE VOLTAGE
1500 V
Published datasheet
PEAK NEGATIVE PULSE GRID VOLTAGE
250 V
Published datasheet
NEGATIVE DC GRID VOLTAGE
-50 V
Published datasheet
CATHODE CURRENT
20 mA
Published datasheet
AVERAGE CATHODE CURRENT
20 mA
Published datasheet
PEAK CATHODE CURRENT
70 mA
Published datasheet
Other
HEATER WARM-UP TIME
11 s
Published datasheet; operating column 1
DC AND PEAK
200 V
Published datasheet
EACH PLATE
3.5 W
Published datasheet; operating column 1
EACH PLATE
3 W
Published datasheet; operating column 2
Data set 04
1968 General Electric Co
Published operating points and test conditions from this source.
SECTION 1
Triode
Other
Peak Positive Pulse Plate Voltage
1500 V
VerticalDeflection
Peak Cathode Current
300 mA
VerticalDeflection
Characteristic
Plate Voltage
250 V
EachSection
Amplification Factor
16.5
EachSection
Plate Resistance
5300 ohm
EachSection
Transconductance
3100 uS
EachSection
Plate Current
11.5 mA
EachSection
Data set 05
1971 RCA HB3 Binder 5 of 7
Published operating points and test conditions from this source.
SECTION 1
Triode
Characteristics
''4. Heater arrangement
4
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Voltage — published value 1
12.6 V
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Voltage — published value 2
6.3 V
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Current — published value 1
300 mA
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Current — published value 2
600 mA
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Warm-up time (Average
11
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Grid to plate — published value 1
2.6
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Grid to plate — published value 2
2.6
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
and heater — published value 1
3.2
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
and heater — published value 2
3.2
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
and heater — published value 1
0.5
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
and heater — published value 2
0.4
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
plate of unit No.2
8
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Pin 1 -Plate of — published value 1
1
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Pin 1 -Plate of — published value 2
6
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Pin 2 -Grid of — published value 1
2
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Pin 2 -Grid of — published value 2
7
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Pin 3 -Cathode of — published value 1
3
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Pin 3 -Cathode of — published value 2
8
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Pins 4d9 -Heater of — published value 1
4
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Pins 4d9 -Heater of — published value 2
9
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Other
PLATE VOLTAGE
300 V
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Negative bias value
50 V
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Positive bias value
0 V
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
CATHODE CURRENT
20 mA
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
PLATE DISSIPATION
3.5 mA
Published value from the filename-designated RCA datasheet block; multiple numbers on one row represent separate limits or heater arrangements.
Data set 06
1975 RCA RC30
Published operating points and test conditions from this source.
SECTION 1
Triode
Characteristic
Heater Voltage (ac/dc)
6.3 volts
Published value from supplied target entry
Heater Current
0.6 ampere
Published value from supplied target entry
Heater Warm-up Time (Average)
11 seconds
Published value from supplied target entry
Plate Voltage
300 volts
Published value from supplied target entry
Cathode Current
20 mA
Published value from supplied target entry
Plate Voltage
250 volts
Published value from supplied target entry
Grid Voltage
-10.5 volts
Published value from supplied target entry
Amplification Factor
16.5
Published value from supplied target entry
Plate Resistance (Approx.)
5300 ohms
Published value from supplied target entry
Transconductance
3100 umhos
Published value from supplied target entry
Plate Current
11.5 mA
Published value from supplied target entry
Grid Voltage (Approx.) for plate current of
50 volts
Published value from supplied target entry
DC Plate Voltage
450 volts
Published value from supplied target entry
Peak Negative-Pulse Grid Voltage
600 volts
Published value from supplied target entry
Peak Cathode Current
300 mA
Published value from supplied target entry
Average Cathode Current
20 mA
Published value from supplied target entry
Grid-Circuit Resistance
2.2 megohms
Published value from supplied target entry
DC Plate Voltage
450 volts
Published value from supplied target entry
Peak Negative-Pulse Grid Voltage
260 volts
Published value from supplied target entry
Peak Cathode Current
70 mA
Published value from supplied target entry
Capacitance
Direct lntei-electrode Capacitances (Approx.) : Unit No.l Unit No
2
Published value from supplied target entry
Grid to Plate
2.6 pF
Published value from supplied target entry
Grid to Cathode and Heater
3.2 pF
Published value from supplied target entry
Plate to Cathode and Heater
0.4 PF
Published value from supplied target entry
Other
Peak Positive-Pulse Plate Voltage* (Absolute maximum)
1500 volts
Published value from supplied target entry
Data set 07
2026 JJ Electronic
Published operating points and test conditions from this source.
SECTION 1
Triode
Characteristic
Transconductance
3100 µS