7-30 Maintenance and Testing Date Code 20000421
SEL-251, -2, -3 Instruction Manual
4. Measure and record the state of all output relays.
5. Inspect the cabling to the serial communications ports and be sure a communications device is
connected to at least one communications port.
Troubleshooting Table
All Front Panel LEDs Dark
1. Power is off.
2. Blown power supply fuse.
3. Input power not present.
4. Self-test failure.
5. Target command improperly set.
Note: For 1, 2, 3, and 4 the ALARM relay contacts should be closed.
System Does Not Respond to Commands
1. Communications device not connected to system.
2. Relay or communications device at incorrect baud rate or other communication parameter
incompatibility, including cabling error.
3. System is processing event record. Wait several seconds.
4. System is attempting to transmit information, but cannot due to handshake line conflict.
Check communications cabling.
5. System is in the XOFF state, halting communications. Type <CTRL>Q to put system in
XON state.
Tripping Output Relay Remains Closed Following Fault
1. Contact inputs improperly wired.
2. Output relay contacts burned closed.
No Prompting Message Issued to Terminal Upon Power-Up
1. Terminal not connected to system.
2. Wrong baud rate.
3. Terminal improperly connected to system.
4. Other port designated AUTO in the relay settings.
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