Lake Shore Model 421 Gaussmeter User’s Manual
Service
6-3
120
100/120/220/240 V
10% +6% Voltage
50-60 Hz 40 VA MAX
100/120V
220/240V
0.5 A T 250V
0.25 A T 250V
0.25×1.25"
5×20mm
Line Cord
Input
Power Switch
O
=Off,
l
=On
Fuse
Drawer
Screwdriver
Slot
F-421-6-1.eps
Figure 6-1. Power Fuse Access
6.4 FUSE
REPLACEMENT
Below is the procedure to remove and replace a line fuse. There are two basic power configurations:
U.S. and International. Units produced for use in the U.S. have a single fuse on the hot. Units produced
for International use have a double fuse for the hot and neutral. To change line input from the factory
setting, use the appropriate fuse in the connector kit shipped with the instrument. Test fuse with
ohmmeter. Do not rely on visual inspection of fuse.
WARNING: To avoid potentially lethal shocks, turn off controller and disconnect it from AC
power before performing these procedures.
CAUTION:
For continued protection against fire hazard, replace only with the same fuse type and
rating specified for the line for the line voltage selected.
1. Locate line input assembly on the instrument rear panel. See Figure 6-1.
2. Turn power switch Off (
O
).
3. Remove instrument power cord.
4. With a small screwdriver, release the drawer holding the line voltage selector and fuse.
5. Remove existing fuse(s). Replace with proper Slow-Blow fuse ratings as follows:
100/120 V
0.5 A T 250 V
0.25 × 1.25 inches
220/240 V
0.25 A T 250 V
5 × 20 mm
6. Re-assemble line input assembly in reverse order.
7. Verify voltage indicator in the line input assembly window.
8. Connect instrument power cord.
9. Turn power switch On (
l
).
