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1.
The amplifier control circuits are dependent on the driv-
er.
2.
There are,
basically,
two distinct systems.
One series of
circuits in the driver and the amplifier are for inter-
locks,
air switches and grid bias functions.
Because of
the nature of the
system,
all functions must be complete
and satisfied in the driver before indications cn occur
in the amplifier.
3.
The other control circuits have to do with driver and
amplifier overload functions.
When an overload occurs,
the associated relay closes.
When this occurs,
three
events happen -
a.
The indicator light is extinguished.
b.
110 V.
d.c.
applied through R708 holds the relay
closed.
c.
The contacts of section A of the relay complete the
circuit to the recycle unit.
If the " tune- operate"
switch is in the tune position,
the re-
1.
7
y which has experienced the overload must be de- energized by
pushing the manual reset button.
If the transmitter is in the operate position,
the transmitter
will recycle and try to turn itself on.
The filament voltage on the amplifier will chane with output
power.
This is because of power line loading.
The filament
voltage during operation should be maintained at
7.5
volts.
The balance control,
R806,
has an effect on the individual
grid bias voltage and is used to adjust the plate and screen
currents to similar values.
These currents should be within 10% so that there is somewhat
equal dissipation of each tube.
The grounding hooks which are a part
of the transmitter should
be used when making repairs and adjustments on the transmitter.
These devices must be returned to their hook before the trans-
mitter is operated because this is part of the interlock system.
REMOTE CONTROL Fa.CILITIZS
To remote control the FM-20B,three remote control functions
will be required.
Those are:
t*
1.
The fail-safe control function required by the FCC.
2.
A momentary " off", momentary " on"
function required to
turn the driver plate voltage off and on.
3.
raise- lower function for controlling the motor that is
used to drive the plabe voltage powerstat.
6
/
2
2/61
-17-
FM- 20B
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