|
Zenith Model 7-D-138,
1937. The large tombstone cabinet features seven tubes, multi-band
tuning, an 8-inch electro-dynamic speaker, and voice-music-high fidelity
control.
6A8
Pentagrid Converter
| Substitutes |
Base Diagram |
| 6D8G*, 6A8MG, 6A8GTX, 6A8GT, 6A8G, 6D8* |
|
| Notes: * -
Parallel filaments |
6K7
Remote Cutoff RF Pentode
| Substitutes |
Base Diagram |
| 5732, 6U7G, 6K7MG, 6K7GTX, 6K7GT, 6K7G, 6U7, 6J7, 6S7 |
|
6H6
Duo Diode
| Substitutes |
Base Diagram |
| WT261, WTT103, 6H6WGT, 6H6MG, 6H6GT/G, 6H6GT, 6H6G |
|
6F5
High Mu Triode
| Substitutes |
Base Diagram |
| 6F5MG, 6F5GT, 6F5G |
|
25A6
Power Amplifier Pentode
| Substitutes |
Base Diagram |
| 25A6MG, 25A6GT/G, 25A6GT, 25A6G, 25W6 |
|
|
MECHANICAL DATA
| Bulb |
MT-8B |
| Base |
7-Prong Octal Base |
| Basing |
7S |
ELECTRICAL DATA
HEATER CHARACTERISTICS
| Heater Voltage |
25.3 |
Volts |
| Heater Current |
0.3 |
Amps |
MAXIMUM RATINGS
| Plate Voltage |
160 |
Volts |
| Screen Voltage |
135 |
Max |
| Plate Dissipation |
5.3 |
Watts |
| Screen Dissipation |
1.9 |
Watts |
CHARACTERISTICS AND TYPICAL OPERATION
CLASS A1 AMPLIFIER (Each Section)
| Plate Voltage |
95 |
135 |
160 |
Volts |
| Screen Voltage |
95 |
135 |
120 |
Volts |
| Grid Voltage |
-15 |
-20 |
-18 |
Volts |
| Peak A-F Grid Voltage |
15 |
20 |
18 |
Volts |
| Zero-Signal Plate Current |
20 |
27 |
33 |
Ma |
| Max-Signal Plate Current |
22 |
29 |
36 |
Ma |
| Zero-Signal Screen Current |
4 |
8 |
6.5 |
Ma |
| Max-Signal Screen Current |
8 |
14 |
12 |
Ma |
| Plate Resistance (Approx.) |
45000 |
35000 |
42000 |
Ohms |
| Transconductance |
2000 |
2450 |
2375 |
?mhos |
| Load Resistance |
4500 |
4000 |
5000 |
Ohms |
| Total Harmonic Distortion |
11 |
9 |
10 |
Percent |
| Max-Signal Power Output |
0.9 |
2.0 |
2.2 |
Watts |
|
|
25Z6
Rectifier Doubler
| Substitutes |
Base Diagram |
| 25Z6WGT, 25Z6MG, 25Z6GT/G, 25Z6GT, 25Z6G |
|
STANDARD RMA CONDENSER COLOR CODE
THE CAPACITIES OF MANY SMALL
CONDENSERS ARE DESIGNATED BY A SERIES OF THREE COLORED DOTS, STAMPED ON AN
ARROW-SHAPED FORM ON THE CONDENSERS, IN ACCORDANCE WITH THE STANDARD RMA
CONDENSER COLOR CODE.
THESE DOT SYMBOLS ARE TO BE READ
FROM THE TAIL TOWARD THE HEAD OF THE ARROW. THE CAPACITY IS EXPRESSED IN
MICRO-MICRO FARADS. THE FIRST DOT INDICATES THE FIRST FIGURE OF THE
CAPACITY, THE SECOND DOT INDICATES THE SECOND FIGURE AND THE THIRD DOT
INDICATES THE NUMBER OF ZEROES FOLLOWING THE FIRST TWO FIGURES.
EXAMPLE
Nostalgia Air RMA Color Code References
|
Helpful Radio
Restoration Links:
Nice Audio and Electronic Links
|
|
|
