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Figure 6-18
lMA
F'S
-
-
Plate current is indicated by measuring the
amount of current in the cathode circuit of the
final amplifiers.
For
500 milliamperes
of
cathode current in the cathode circuit (com-
bined resistance-capacitance
cathode circuits),
there will be 1 milliampere of current in the
meter.
1/116
2200
ALe ADJUST
.OJ
Plate
(Figure
6-17)
APPLIED
ALC
-
Current in the grid circuits of final amplifiers
Vl0 and V1I is shunted through the meter, which
has a 1 milliampere full-scale,
100
Q
move-
ment. This provides a 0-1 ma range in this
position of the Meter switch.
Gr id (F igure 6-16)
HI17
33K
CI16
B+
V3
METERING CIRCUITS
The meter is balanced for no-signal conditions
(zero current) in the cathode circuit of isolation
amplifier V3 by ALe Adjust control R120.When
a sideband signal is transmitted andALC (nega-
tive) voltage is applied to the grid ofV3, the tube
draws less current, causing the cathode to be-
come less positive and the screen to become
more positive. The voltage difference developed
across the meter causes a current through the
meter, which indicates ALC action in the Trans-
mitter.
All tube filaments receive voltage from a sep-
arate power transformer filament winding (yel-
low, green, and yellow-green leads).
The primary winding of the power transformer
is fused and a TV type quick-disconnect line
cord is used.
Automatic Level Control (Figure 6-18)
The AC voltage obtained from the low voltage
secondary winding (brown lead) is approximately
125 volts (rms). A half-wave rectifier circuit
conststing of diode D2, capacitors
C404 and
C405, and resistor
R412, removes the 60 Hz
ripple from the bias voltage. With suitable
divider networks
(see
the Schematic Diagram),
variable bias {-45 to -70 volts) and various fixed
bias levels are obtained.
Figure 6-17
Figure 6-16
·REPRESENT
COMBINED
=-
RESISTANCE AND CAPACITANCE
-
-
BIAS SUPPLY
GRID
-
ioon
1tJI A
rs
-
•
-"'-.015
loon
rMA
FS
CI04 __.__
.005I
RJ3
4700
•
.015
•
3
.3.n.
RFC 102
.5MH
6146
6146
Vll
Vl0
Vll
6146
Vl0
6146
Page 137
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