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Chapter 2, INSTALLATION AND INITIAL CHECKS
2-2
barrel selectors internal to the line input assemblies on the rear panels of the two
units. Instruments are normally shipped from the factory with the line voltage
selectors set to 110-130 V AC, unless they are destined for an area known to use a
line voltage in the 220-260 V range, in which case, they are shipped configured for
operation from the higher range.
The line voltage setting can be seen through a small rectangular window in the line
input assemblies on the rear panels of the instruments (figure 2-1). If the number
showing is incorrect for the local line voltage (refer to table 2-1), then the barrel
selectors will need to be repositioned as follows.
Observing the instrument from the rear, note the plastic door forming part of the
input assembly (figure 2-1). When the line cord is removed from the rear-panel
connectors, the plastic door can be opened outwards by placing a small, flat-bladed
screwdriver in the slot and levering gently. This gives access to the fuse and to the
voltage barrel selector. Remove the barrel selector with the aid of a small
screwdriver or similar tool. With the barrel selector removed, four numbers become
visible on it: 100, 120, 220, and 240, only one of which is visible when the door is
closed. Table 2-1 indicates the actual line voltage range represented by each number.
Position the barrel selector such that the required number (see table 2-1) will be
visible when the barrel selector is inserted and the door closed.
Figure 2-1, Line Input Assemblies (Left - Main Console; Right - 7124 RCU)
VISIBLE #
Next check the fuse rating. For operation from a nominal line voltage of 100 V or
120 V, use a 20 mm slow-blow fuse rated at 1.0 A, 250 V. For operation from a
nominal line voltage of 220 V or 240 V, use a 20 mm slow-blow fuse rated at 0.5 A,
250 V.
To change the fuse, first remove the fuse holder by pulling the plastic tab marked
with an arrow. Remove the fuse and replace with a slow-blow fuse of the correct
voltage and current rating. Install the fuse holder by sliding it into place, making sure
the arrow on the plastic tab is pointing downwards. When the proper fuse has been
installed, close the plastic door firmly. The correct selected voltage setting should
now be showing through the rectangular window. Ensure that only fuses with the
VOLTAGE RANGE
100
90
120
110
220
200
240
220
Table 2-1, Range vs. Barrel Position
-
110 V
-
130 V
-
240 V
-
260 V
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