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3
GENERAL
SAFETY 1,NTERLOCK DC INPUT POWER
Refer to the Chassis Photograph (Page
87)
for the location
of the interlock. When the amplifier top cover
is
in place,
the insulator on the underside of the cover opens the
interlock, and the high voltage circuit
is
operational. When
the top cover
is
removed, the interlock closes and connects
the high voltage circuit to chassis. This connection will
discharge the filter capacitor bank and eliminate a shock
hazard.
WARNING:
If the Amplifier is turned ON when the
amplifier cover
is
removed,
the high voltage power supply
will be short circuited and may be damaged. If this occurs,
DO NOT touch any
part
of the high voltage supply with
your hands until all possible high voltage points have been
checked
with a
separate
voltmeter.
CIRCUIT BREAKERS
Push in the red buttons on the two circuit breakers and note
their position. When a circuit breaker opens, the red buttons
will protrude farther and will be easily noticed.
If one or both circuit breakers open during operaTmn of the
Amplifier, turn the amplifier POWER switch OFF; then
push the red buttons in to their former position, wait a few
seconds, and push the POWER switch to ON. If the breakers
In grounded grid amplifier operation, a considerable portion
of the driving power
is
fed through the amplifier tube. The
Amplifier output is the approximate sum of the driver
output and the power added by the Amplifier. Both the
driver and amplifier input powers must therefore be
considered when calculating DC input power.
DRIVING POWER
This Amplifier
is
designed to operate at full ratings (see
Specifications) when driven by an exciter delivering
approximately
100
watts of RF output. An exciter of lower
power output may be used as a driver, but the Amplifier's
output will be less. If you use an exciter that delivers more
than
100
watts,
carefully adjust the driving power to avoid
"overdrive" and the creation of spurious signals which
create needless interference to others. The use of the
Heathkit Model
610
Monitor Scope
is
highly recommended
for continuous output monitoring. The display on an
oscilloscope
is
the best readily available way of determining
the amplitude of the voice peaks which, if excessive, can
cause "flat topping" and the radiation of distortion
products.
will not stay closed, push the POWER witch OFF and
locate the reason for the overload.
IMPORTANT: In no case should the MICICW Level of your
exciter
be
advanced beyond the point where the Amplifier
TUBES
REL. PWR. indication ceaseszto increase.
If
the level control
is
turned past this point, nonlinear operation may
be
The Amplifier uses "instant heating" type tubes. Therefore,
produced.
after tuneup, you can turn the Amplifier off until you are
ready to use
it.
Then, you can use the Amplifier
immediately after
it
is
turned on.
ALC (Automatic Level Control)
It
is
not abnormal for the tube plates to show a dull red
color. If the plates show a bright orange or yellow color,
When the Amplifier
is
overdriven, the ALC circuitry creates
tuning and drive conditions should be investigated
a
negative
voltage
which
is
fed
back
to
the
exciter
to
reduce
immediately, and necessary corrections should be made.
its
gain and help prevent "flat topping."
7
After prolonged usage, let the Amplifier run for several
minutes without excitation, so the fan will cool the tubes
before the Amplifier
is
turned off.
_r
Protective circuitry of this nature
is
a valuable circuit
element, but
it
is
not a substitute for proper adjustment of
the exciter drive.
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