Data set 01
1950 Sylvania
Published operating points and test conditions from this source.
SECTION 1
Triode
Characteristic
Plate Current
1 mA
PlateVoltage=250V
Voltage - Triode (with diode, heptode or hexode) ·Diode-Diode-Triode
12BT6
Double-diode high-mu triode for detector, control-voltage, and voltage-amplifier functions. The paired diodes provide signal rectification while the triode supplies substantial voltage gain in series-string receiving equipment.
Directly heatedCold cathodeCommon cathodeDissimilar
- Sections
- 3
- Base
- 7BT-0-2
- Socket code
- B7G
- Base pins
- 7
- Nominal heater
- 12.6 V / 150 mA
Description
12BT6 — Double-Diode Triode
The 12BT6 is a miniature, double-diode triode vacuum tube designed for service as a combined high-mu triode voltage amplifier and double diode detector. Constructed with a 7-pin miniature button base, the tube is engineered to deliver sufficient output voltage to drive most beam power tubes to their full power output. Its design features high-perveance diodes that provide efficient rectification at low signal levels, alongside a low diode-to-triode grid capacitance to minimize unwanted audio coupling between the sections.
Mechanical Specifications and Pin Connections
The 12BT6 is housed in a T-5 1/2 glass bulb and utilizes an E7-1 miniature button 7-pin base. The physical dimensions of the tube are compact, allowing for versatile installation in space-constrained layouts.
- Maximum Diameter: 3/4 inch
- Maximum Overall Length: 2 5/8 inches
- Maximum Seated Height: 2 3/8 inches
- Mounting Position: Any
The tube uses the 7BT (or 7BT-0-2) basing arrangement. The pin connections, viewed from the bottom of the base, are assigned as follows:
| Pin | Connection |
|---|---|
| Pin 1 | Triode Grid |
| Pin 2 | Cathode, Diode Shield |
| Pin 3 | Heater |
| Pin 4 | Heater |
| Pin 5 | #2 Diode Plate |
| Pin 6 | #1 Diode Plate |
| Pin 7 | Triode Plate |
Heater and Maximum Ratings
The 12BT6 features an indirectly heated, coated unipotential cathode. The heater is designed to operate on either alternating or direct current. The maximum ratings are established under the Design Center system (interpreted according to RMA Standard M8-210):
| Parameter | Value |
|---|---|
| Heater Voltage (AC or DC) | 12.6 V |
| Heater Current | 150 mA |
| Maximum Plate Voltage (DC) | 300 V |
| Maximum Heater-Cathode Voltage | 90 V |
| Maximum Positive DC Grid Voltage | 0 V |
| Maximum Continuous Diode Current (each plate) | 1.0 mA |
Electrical Characteristics and Operating Points
The triode section of the 12BT6 is characterized by a high amplification factor of 70, making it highly effective for voltage amplification. The typical operating conditions for the triode unit are specified at two distinct plate voltages:
| Parameter | Operating Point I | Operating Point II |
|---|---|---|
| Plate Voltage (DC) | 100 V | 250 V |
| Grid Voltage (DC) | -1 V | -3 V |
| Plate Current | 0.8 mA | 1.0 mA |
| Plate Resistance | 54,000 ̩ | 58,000 ̩ |
| Transconductance | 1,300 mhos | 1,200 mhos |
| Amplification Factor | 70 | 70 |
The diode units are designed for detection and rectification. At an applied potential of 10 volts DC, each diode plate exhibits the following current characteristics:
- Minimum Diode Current: 1.5 mA
- Average Diode Current: 4.0 mA
Interelectrode Capacitances
The direct interelectrode capacitances of the 12BT6 are low, which helps prevent signal degradation and coupling. The capacitances are measured both with and without an external shield (specifically, RMA Shield #316 connected to Pin 2):
| Measurement | Without Shield | With Shield |
|---|---|---|
| Diode #1 to Cathode / Input: #1p to (h+k+i.s.) | 1.0 F | 1.0 F |
| Diode #2 to Cathode / Input: #2p to (h+k+i.s.) | 1.0 F | 1.0 F |
| Diode #1 Plate to Triode Grid (maximum) | 0.013 F | 0.01 F |
The low maximum capacitance of 0.013 F (or 0.01 F with shield) between the first diode plate and the triode grid is critical for reducing audio coupling between the detector and amplifier sections of the tube.
Related Designations
The 12BT6 is closely associated with the 6BT6 designation. The two types share the same general double-diode triode configuration and characteristics, with the primary distinction being the heater requirements.
Technical Summary
The 12BT6 is a miniature, 7-pin double-diode triode featuring a high-mu triode section (amplification factor of 70) and two high-perveance diode units sharing a common unipotential cathode. Operating with a 12.6 V, 150 mA heater, the tube is optimized for combined detector and voltage amplifier service in compact receiver designs, capable of supplying sufficient output voltage to drive standard beam power output stages.
Socket description
Miniature 7-contact
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- 7BT-0-2
- Socket code
- B7G
- Base pins
- 7
- Nominal heater voltage
- 12.6 V
- Nominal heater current
- 150 mA
- Parallel heater voltage
- -
- Parallel heater current
- -
- Series capable
- No
7BT-0-2 - Terminal pinout
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
Section ratings
3 physical sections, each with unique specifications.
Section 1
Triode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 68000 Ω
- Transconductance
- 0.0012 S
- Amplification factor
- 70
- Max plate voltage
- 300 V
Values promoted from the supplied Sylvania source where explicitly published.
Section 2
Diode
X-ray radiationInterelectrode capacitances
No fixed ratings are recorded for this section.
Values promoted from the supplied Sylvania source where explicitly published.
Section 3
Diode
X-ray radiationInterelectrode capacitances
No fixed ratings are recorded for this section.
Values promoted from the supplied Sylvania source where explicitly published.
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
1961 Tung Sol
Published operating points and test conditions from this source.
SECTION 1
Triode
Other
Heater voltage
12.6 V
Nominal
Heater current
150 mA
Nominal
Plate voltage
100250 V
Typical operating conditions
Plate current
0.81 mA
Typical operating conditions
SECTION 2
Diode
Other
Heater voltage
12.6 V
Nominal
Heater current
150 mA
Nominal
Plate voltage
100250 V
Typical operating conditions
Plate current
0.81 mA
Typical operating conditions
SECTION 3
Diode
Other
Heater voltage
12.6 V
Nominal
Heater current
150 mA
Nominal
Plate voltage
100250 V
Typical operating conditions
Plate current
0.81 mA
Typical operating conditions