WhitakerAudio J C Whitaker 20 W Stereo Audio Amplifier, Manual

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20 W Stereo Audio Amplifier
· When a voltage dropping resistor is used, the minimum value of resistor that will assure tube
operation within the boundary of the curve can be determined by the relation
Where:
R
g 2
= minimum value for the voltage-dropping resistor in ohms
E
c 2
= selected screen grid voltage in volts
E
cc 2
= screen grid supply voltage in volts
P
c 3
= screen grid input in watts corresponding to E
c 2
10.1.2 6973 Beam Power Tube
The 6973 is a 9-pin compact beam power tube used in high-fidelity audio equipment. The device
pinout is given in Figure 10.3. Operating characteristics are charted in Figure 10.4.
( )
2 2 2
2
2
c cc c
g
c
E E E
R
P
−
≥
This curve also applies to types
in which grids #2 and #4 are connected
together within the tube
Grid #2 input expressed as a percentage of maximum grid #2 input rating
100
80
50
40
20
0 20 40 60 80 100 120
Grid #2 voltage expressed as a percentage of maximum
grid #2 supply voltage rating
Area of
permissible operation
Figure 10.2 Grid #2 (screen grid) input rating curve.
Figure 10.3 Terminal pinout of the 6973.
NC
H
H
P
2
G
1
G
1
G
3
K, G
2
G
Legend:
H = heater
K = cathode
G = grid #1, 2, 3
P = plate
1
2
3
4
5
6
7
8
9