Voltage Dual Triode Pentode ·Pentode-Triode-Triode
Heater variant of the 6BD11 combining high-mu and medium-mu triodes with a sharp-cutoff pentode for television signal-amplifier applications.
The 15BD11A is an indirectly heated, multi-unit vacuum tube containing three independent active sections within a single Compactron T-9 glass envelope. It features a high-mu triode (Section 1), a medium-mu triode (Section 2), and a sharp-cutoff pentode. The tube is designed for television receiver applications, specifically serving as a general-purpose amplifier, sync separator, and video amplifier.
The 15BD11A utilizes Compactron T-9 construction with a glass envelope and a 12-pin button base (E12-70). The physical layout is defined by the 9-58 outline, with the following physical dimensions:
The tube uses the 12DP basing arrangement. The pin connections, viewed from the bottom of the base, are assigned as follows:
| Pin | Connection |
|---|---|
| Pin 1 | Cathode (Triode Section 1) |
| Pin 2 | Plate (Triode Section 2) |
| Pin 3 | Grid (Triode Section 2) |
| Pin 4 | Cathode (Triode Section 2) |
| Pin 5 | Plate (Triode Section 1) |
| Pin 6 | Heater |
| Pin 7 | Heater |
| Pin 8 | Grid No. 1 (Pentode Section) |
| Pin 9 | Grid No. 2 / Screen Grid (Pentode Section) |
| Pin 10 | Grid No. 3 / Suppressor Grid and Internal Shield |
| Pin 11 | Plate (Pentode Section) |
| Pin 12 | Grid (Triode Section 1) |
The 15BD11A is designed for series-string heater operation, featuring a controlled warm-up time. Its heater ratings and heater-cathode voltage limits are:
| Parameter | Value |
|---|---|
| Heater Voltage | 14.7 V |
| Heater Current | 450 mA |
| Heater Warm-up Time | 11 seconds |
| Max. Heater-Cathode Voltage (Heater Negative to Cathode) | 200 V (Total DC and Peak) |
| Max. Heater-Cathode Voltage (Heater Positive to Cathode, DC) | 100 V |
| Max. Heater-Cathode Voltage (Heater Positive to Cathode, Total) | 200 V (Total DC and Peak) |
The 15BD11A shares its heater voltage and current ratings with the 15BD11, but differs from the 6BD11, which operates at a nominal heater voltage of 6.3 V and a heater current of 1050 mA.
The ratings of the three independent sections are defined under the Design Maximum Rating System. A key distinction of the 15BD11A compared to the related 15BD11 and 6BD11 is its increased screen dissipation capability.
| Rating Parameter | Triode Section 1 | Triode Section 2 | Pentode Section |
|---|---|---|---|
| Maximum Plate Voltage | 330 V | 330 V | 330 V |
| Maximum Screen-Supply Voltage | — | — | 330 V |
| Maximum Positive DC Grid Voltage | 0 V | 0 V | 0 V (Grid No. 1) |
| Maximum Plate Dissipation | 1.5 W | 2.0 W | 4.0 W |
| Maximum Screen Dissipation | — | — | 1.5 W |
| Max. Grid Circuit Resistance (Fixed Bias) | 0.5 M̧ | 0.5 M̧ | 1.0 M̧ |
| Max. Grid Circuit Resistance (Cathode Bias) | 1.0 M̧ | 1.0 M̧ | 1.0 M̧ |
Note: The maximum screen dissipation for the 15BD11A is 1.5 Watts, whereas the 15BD11 and 6BD11 are limited to 1.1 Watts.
The direct interelectrode capacitances of the 15BD11A are measured without an external shield. The coupling between sections is minimized but present, as detailed below:
The three sections of the 15BD11A exhibit distinct electrical characteristics optimized for their respective roles in television circuitry.
Operating as a Class A1 amplifier, Triode Section 1 provides high voltage gain:
Triode Section 2 is designed for medium-mu applications, operating with cathode bias:
The pentode section is characterized under two typical operating conditions:
| Parameter | Condition A | Condition B |
|---|---|---|
| Plate Voltage | 35 V | 135 V |
| Screen Voltage (Grid No. 2) | 135 V | 135 V |
| Grid No. 1 Voltage | 0 V | — |
| Cathode Bias Resistor | — | 100 ̩ |
The 15BD11A is a versatile Compactron triple-section tube containing a high-mu triode, a medium-mu triode, and a sharp-cutoff pentode. Operating with a 14.7 V, 450 mA heater and an 11-second controlled warm-up time, it is optimized for series-string television receiver designs. Its unique design maximum ratings, particularly the 1.5 W screen dissipation limit, distinguish it from the closely related 15BD11 and 6BD11. With its independent cathodes and low inter-section coupling capacitances, the 15BD11A provides a highly integrated solution for amplification, sync separation, and video processing.
Duodecar 12-contact
General specifications
Properties common to every published source and operating point.
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
3 physical sections, each with unique specifications.
Section 1
Sylvania 15BD11A first high-mu triode of two dissimilar physical triodes and video pentode. 14.7 V 450 mA series heater. Equivalent to 6BD11 except heater and separate pentode screen rating. Maximum plate 330 V, dissipation 1.5 W. Typical at Va 200 V and grid -2 V: gm 5.5 mA/V, amplification factor 68, plate resistance ~12400 ohms. Sylvania publishes individual and inter-section capacitances. Other triode is medium-mu and has different ratings.
Section 2
Sylvania 15BD11A second, medium-mu triode, physically distinct from first high-mu triode. Maximum anode voltage 330 V and dissipation 2 W; typical at Va 200 V, 220-ohm cathode bias resistor: gm 4.4 mA/V, mu 41, plate resistance 9400 ohms, plate current ~9.2 mA. Shared 14.7 V 0.45 A heater variant of 6BD11. Interelectrode capacitances published.
Section 3
Sylvania 15BD11A sharp-cutoff video-amplifier pentode, with two dissimilar separate triodes. Maximum plate 330 V, dissipation 4 W, screen supply 330 V; Sylvania specifically gives 1.5 W max screen dissipation for 15BD11A rather than 6BD11's 1.1 W. Typical pentode gm ~10.4 mA/V and plate resistance ~45 kΩ based on verified 6BD11 family electrical equivalence, conditioned on its published operating point. Capacitances specified. Series heater 14.7 V at 0.45 A.
Source-dependent data
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.
Data set 01
Published operating points and test conditions from this source.
HeaterOrFilamentVoltageNominal
14.7 V
HeaterOrFilamentCurrentNominal
450 mA
Maximum Screen Dissipation
1.6 W
PentodeSection