U.2.40
SEL-421 Relay
User’s Guide
Date Code 20090715
Installation
Connection
Power Supply Fuse Replacement
You can replace a bad fuse in an SEL-421 power supply, or you can return the
SEL-421 to SEL for fuse replacement. If you decide to replace the fuse,
perform the following steps to replace the power supply fuse:
Step 1. Follow your company standard to remove the relay from
service.
Step 2. Disconnect power from the SEL-421.
Step 3. Remove the relay from the rack or panel.
Step 4. Retain the
GND
connection, if possible, and ground the
equipment to an ESD mat.
Step 5. Remove the communications cable connected to the front-panel
serial port, if applicable.
Step 6. Remove the rear-panel
EIA-232 PORT
mating connectors.
Unscrew the keeper screws and disconnect any serial cables
connected to the
PORT 1
,
PORT 2
, and
PORT 3
rear-panel
receptacles.
Step 7. Loosen the four front-panel screws (they remain attached to the
front panel), and remove the relay front panel.
Step 8. Remove the 34-pin ribbon cable from the front panel by
pushing the extraction ears away from the connector.
Step 9. Disconnect the power, the interface board, and the analog input
board cables from the main board.
Step 10. Remove the screw terminal connectors.
a. Loosen the attachment screws at each end of the
100-addresses, 200-addresses, and 300-addresses screw
terminal connectors.
b. Pull straight back to remove.
Step 11. Remove the top chassis plate by unscrewing seven screws from
the chassis.
Step 12. Pull out the drawout tray containing the main board.
Step 13. Pull out the drawout tray containing the I/O interface board(s).
Step 14. Locate the power supply. Fuse F1 is at the rear of the power
supply circuit board (see
).
Step 15. Examine the power supply for blackened parts or other
damage. If you can see obvious damage, reinstall all boards and
contact SEL to arrange return of the relay for repair.
Step 16. Remove the spent fuse from the fuse clips.
Step 17. Replace the fuse with an exact replacement (see
for
the proper fuse for your power supply).
Step 18. Reinstall the interface board.
Step 19. Reinstall the SEL-421 main board, and reconnect the power,
the interface board, and the analog input board cables.
Step 20. Replace the chassis top on the relay and secure it with seven
screws.
Disconnect or de-energize all external
connections before opening this
device. Contact with hazardous
voltages and currents inside this
device can cause electrical shock
resulting in injury or death.
!
DANGER
Have only qualified personnel service
this equipment. If you are not
qualified to service this equipment,
you can injure yourself or others, or
cause equipment damage.
!
WARNING
Equipment components are sensitive
to electrostatic discharge (ESD).
Undetectable permanent damage
can result if you do not use proper
ESD procedures. Ground yourself,
your work surface, and this
equipment before removing any
cover from this equipment. If your
facility is not equipped to work with
these components, contact SEL
about returning this device and
related SEL equipment for service.
!
CAUTION
Summary of Contents for 421
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