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Sect. II Page 2
DC VOLTAGE - The operating circuit of this in-
dicator light is controlled by the DC VOLTAGE
switch, and the light glows red when the switch is
at ON to indicate that voltage is applied to the DC
VOLTAGE output terminals.
AC VOLTAGE Switch -
This SPST toggle switch is in the primary circuit
of the power transformer. With the AC VOLTAGE
switch at ON, line voltage is closed to power trans-
former T1.
DC VOLTAGE Switch -
There is no voltage on the
DC
VOLTAGE output ter-
minals until the DC VOLTAGE switch is at the ON
position. When operated, this DPST toggle switch:
'(1) connects the positive d-c bus
to
the
DC
VOLTAGE
output terminals and (2) closes the circuit to the
DC
VOLTAGE indicator light.
Output Terminals -
Both the AC VOLTAGE and DC VOLTAGE output
terminals are of the binding-post type, will accom-
modate either a banana plug or wire, and are so
arranged that any banana plug with 3/4-inch spacing
may be used.
AC VOLTAGE -
There are two pairs of output terminals associated
with the a-c voltage supply. Depending on how the
terminal connections are made (see paragraph 2-3
below), the Model 71lA may be arranged to supply
the following a-c voltages:
6.3 volts at 3 amperes (two circuits), or
6.3 volts at 6 amperes (one circuit),
or
12.6 volts at 3 amperes (one circuit, tapped
at 6.3 V).
DC VOLTAGE -
There is one pair of output terminals for the regu-
lated d-c voltage supply:
+
and -. The binding-post
nuts for the
+ and -
terminals are insulated. Neither
the
+
nor the - terminal is connected to the chassis
within the instrument so that the d-c supply may be
operated either above or below ground
by
appropriate
external connedion to ground.
On
the same mounting plate with the
+
and - termi-
nals is a terminal (G) which is ccnnected to the in-
strument chassis. The G terminal is cmnected to
earth ground when the power-cable connector is
plugged into a grounded female connector.
FUSE -
The fuseholder, which is mounted on the rear plate
of the instrument, contains the time-delay cartridge
fuse which protects the input circuit. Before start-
ing to install a new fuse, check that the power cable
is disconnected from the line. Replacement fuses
must be of the slow-blow type: 1. 6-ampere fuse
for 115-volt operation or a O. 8-ampere fuse for
230-volt operation.
2-2
OPERATING PROCEDURE
Be sure the Model 711A is so placed that nothing
can obstruct the ventilating louvers in the sides of
the cabinet. Safe operating temperatures with the
cabinet depend upon free air flow through the louvers.
a.
Before operating the instrument for the first
time, see paragraph 4-7, Meter Zero Adjustment.
b.
Check that both the AC VOLTAGE and
DC
VOLT-
AGE switches are in the off position. After the
Model 71lA has been plugged into a power source of
specified voltage and frequency, turn the AC VOLT-
AGE switch to ON, and allow a two-minute warmup
period.
NOTE: If the Model 711A is to be operated from a
23Q:Volt source, check (1) that power transformer
T1 is strapped for 230-volt operation (strapping
options are shown on the schematic diagram), and
(2) that fuse F1 is a O. 8-ampere Slo-Blo fuse. See
paragraph 4-8.
With the
DC
VOLTAGE switch still in the off position,
connect the load. For connection arrangements for
the various options, see paragraph 2-3, below.
c.
Check that the COARSE control is in its maxi-
mum counterclockwise (low-voltage) position.
Turn the DC VOLTAGE switch to ON.
d.
To obtain the desired level of d-c voltage, ad-
just the COARSE and FINE controls. The volt-
meter indicates the level of the d-c voltage being
supplied
to
the
+
and - output terminals. If the level
of the d-c supply is below 50 volts, the voltmeter
may be operated on the 50-volt range by depressing
the 50 VOLTS FULL SCALE push-button during the
voltage adjustment procedure.
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