10.23
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Testing, Troubleshooting, and Maintenance
Maintenance
Power Supply Fuse Replacement
You can replace a bad fuse in a relay power supply, or you can return the relay to
SEL for fuse replacement. If you decide to replace the fuse, perform the follow-
ing steps:
Step 1. Follow your company standard to remove the relay from service.
Step 2. Disconnect power from the relay.
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 Figure 10.11).
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 Section 2: Installa-
tion in the product-specific instruction manual for the proper fuse for
your power supply).
Step 18. Reinstall the interface board.
Step 19. Reinstall the 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.
Step 21. Reconnect the cable removed in Step 8 and reinstall the relay front-
panel cover.
Step 22. Reattach the rear-panel connections.
Affix the screw terminal connectors to the appropriate 100-addresses,
200-addresses, and 300-addresses locations on the rear panel.
Disconnect or de-energize all external
connections before opening this
device. Contact with hazardous volt-
ages and currents inside this device
can cause electrical shock resulting in
injury or death.
Have only qualified personnel service
this equipment. If you are not quali-
fied to service this equipment, you
can injure yourself or others, or cause
equipment damage.
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 compo-
nents, contact SEL about returning
this device and related SEL equip-
ment for service.
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