12 Volt Car Radio Tubes

 

 

 

 

 

 

 

 

 

 

 

 

 

By the end of the 1950s the hand writing was on the wall and most engineers and managers knew that tubes were destine to be replaced by transistors.

As often happens when an established technology is threatened by a more advanced one, tube engineers began to innovate to meet the threat.

The two most visible of these innovations were the compactron and the family of tubes that would operate from a plate supply voltage of 12 volts.

Many car radios were made using these tubes for everything except the audio output where a transistor was used. Given time the tube engineers

would have found a way to get 2 or 3 watts from a tube with a plate supply of 12 volts. Unfortunately time ran out on them.

Listed below is the legacy of a dying industry. But don't play taps just yet. There is still a lot of interest in tubes.

 

 

 

 

 

 

 

 

 

 

 

 

 

A space charge tetrode is biased by applying + 12 volts to grid 1 and the signal to grid 2. An LV tetrode is biased in the conventional way.

Signal grid bias is provided by contact potential. A large resistor is connected from the grid to cathode.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Heater (H), Filament (F)

 

 

 

 

 

 

 

 

Type

Function or Configuration

H/F

V

A

Other heater voltages

Plate Dissipation

Max Plate Voltage

Gm

Rp

Base

Notes

12AD6

Medium mu Triode Duo Diode

H

12.6

0.15

-

N. A.

30

1000

15

15 k

7 Pin Mini

Two diodes share cathode with Triode.

12AJ6

Duo Diode Triode

H

12.6

0.15

-

N. A.

30

1200

55

45 k

7 Pin Mini

Two diodes share cathode with Triode.

12DV7

Duo Diode Triode

H

12.6 CT

0.15

-

N. A.

16

750

14

19 k

9 Pin Mini

One cathode for the Triode, another for the two Diodes.

12EL6

Duo Diode Triode

H

12.6

0.15

-

N. A.

30

1200

55

45 k

7 Pin Mini

Two diodes share cathode with Triode.

12FK6

Duo Diode Triode

H

12.6

0.15

-

N. A.

16

1200

7.4

6200

7 Pin Mini

Two diodes share cathode with Triode.

12FM6

Duo Diode Triode

H

12.6

0.15

-

N. A.

30

1300

10

7700

7 Pin Mini

Two diodes share cathode with Triode.

12U7

LV Duo Triode

H

12.6 CT

0.15

-

N. A.

30

1600

20

12.5 k

9 Pin Mini

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Heater (H), Filament (F)

 

 

 

 

 

 

 

 

Type

Function or configuration

H/F

V

A

Section Data

Max Plate Watts

Max Plate Volts

Max Screen Volts

Gm

Rp

Base Type

Notes

12AL8

Space Charge Tetrode plus Triode

H

12.6

0.55

Pentode

N. A.

30

16 G1

15000

480

9 pin mini

Triode u = 13, has separate cathode.

Triode

N. A.

30

-

1000

13 k

12DK7

LV Tetrode plus 2 Diodes

H

12.6

0.5

N/A

0.5

30

30

5000

4000

9 pin mini

 

12DL8

Space Charge Tetrode plus 2 Diodes

H

12.6

0.55

N/A

N. A.

30

16 G1

15000

480

9 pin mini

 

12DS7

Space Charge Tetrode plus 2 Diodes

H

12.6

0.4

N/A

N. A.

16

16 G1

16000

500

9 pin mini

Diodes and Tetrode have common cathode.

12DU7

LV Tetrode plus 2 Diodes

H

12.6

0.25

N/A

N. A.

16

16

6200

6000

9 pin mini

Diodes and Tetrode have common cathode.

12DV8

Space Charge Tetrode plus 2 Diodes

H

12.6

0.375

N/A

N. A.

16

16 G1

8500

900

9 pin mini

Two diodes have common cathode. Tetrode has separate cathode

12DY8

LV Tetrode plus Triode

H

12.6

0.35

Tetrode

N. A.

16

16

6000

5 k

9 pin mini

Separate cathodes.

Triode

N. A.

16

-

2000

10 k

12EM6

LV Tetrode plus Diode

H

12.6

0.5

N/A

0.5

30

30

5000

4000

9 pin mini

Common cathode.

12J8

LV Tetrode plus 2 Diodes

H

12.6

0.325

N/A

N. A.

30

30

5500

6000

9 pin mini

Two diodes have common cathode. Tetrode has separate cathode

12K5

Space Charge Tetrode

H

12.6

0.4

N/A

N. A.

30

16

15000

480

7 pin mini

 

12CN5

Sharp Cutoff Pentode

H

12.6

0.45

N/A

N. A.

16

16

3800

40 k

7 pin Mini

 

12CX6

Sharp Cutoff Pentode

H

12.6

0.15

N/A

N. A.

33

33

3100

40 k

7 pin Mini

 

12EK6

Sharp Cutoff Pentode

H

12.6

0.19

N/A

N. A.

16

16

4200

50 k

7 pin Mini

 

12AC6

Remote Cutoff Pentode

H

12.6

0.15 A

N/A

N. A.

30

30

750

500 k

7 pin Mini

 

12AF6

Remote Cutoff Pentode

H

12.6

0.15 A

N/A

N. A.

16

16

1250

300 k

7 pin Mini

 

12BL6

Semi-Remote Cutoff Pentode

H

12.6

0.15 A

N/A

N. A.

30

30

1350

500 k

7 pin Mini

 

12DZ6

Remote Cutoff Pentode

H

12.6

0.19 A

N/A

N. A.

16

16

3800

25 k

7 pin Mini

 

12F8

Remote Cutoff Pentode Duo Diode

H

12.6

0.15

N/A

N. A.

30

30

1000

330 k

9 pin Mini

Common cathode.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Heater (H), Filament (F)

 

 

 

 

 

 

 

 

Type

Function or configuration

H/F

V

A

Section Data

Max Plate Voltage (volts)

Max Screen Voltage (volts)

Gm

Rp

Base Type

Notes.

12EC8

Medium mu Triode Sharp cutoff Pentode

H

12.6

0.225

Triode

16

-

4700

25

6 k

9 pin mini

Suppressor tied to pentode cathode.

Pentode

16

16

2000

-

750 k

12FR8

Diode, Low mu Triode, and Sharp Cutoff Pentode

H

12.6

0.32

Triode

16

-

1200

10

8.3 k

9 pin mini

Diode plate current = 5 mA. Diode and Triode share a common cathode. Suppressor grid tied to Pentode cathode.

Pentode

16

16

2700

-

400 k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Heater (H), Filament (F)

 

 

 

 

 

 

 

 

Type

Function or Configuration

H/F

V

A

Notes and Comments

Base Type

 

12AD6

Heptode Converter

H

12.6

0.15

This is a 5 grid tube with grids 2 and 4 tied together and brought out to a single pin. Grid 5 is tied to the cathode. Low voltage tube designed for vibrator less car radios.

7 pin mini

 

12EG6

Dual Control Heptode

H

12.6

0.19

This is a 5 grid tube with grids 2 and 4 tied together and brought out to a single pin. Grid 5 is tied to the cathode. Low voltage tube designed for vibrator less car radios.

7 pin mini

 

The application note indicates that both grids 1 and 3 have remote cutoff characteristics for application of AGC to both grids

 

12FX8

Triode Heptode

H

12.6

0.3

Heptode section is a 5 grid tube with grids 2 and 4 tied together and brought out to a single pin. Grid 5 is tied to the cathode. Triode section has mu of 10 and separate cathode. Low voltage tube designed for vibrator less car radios.

9 pin mini

 

12GA6

Heptode Converter

H

12.6

0.15

This is a 5 grid tube with grids 2 and 4 tied together and brought out to a single pin. Grid 5 is tied to the cathode. Low voltage tube designed for vibrator less car radios.

7 pin mini

 


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