Date Code 20010518 Maintenance 10-3
SEL-2020 Instruction Manual
SELF-TESTS
The SEL-2020 continually runs the following self-tests. Any test failure causes an alarm to be
latched and the status report to be issued on Port F.
• RAM. The SEL-2020 continually performs read-write test of RAM.
• ROM. The SEL-2020 continually computes and checks a checksum of ROM.
• EEPROM/Flash. The SEL-2020 continually validates data blocks using checksums.
• Power supply. Threshold comparators (+/- 15 V) are continually checked for tolerance.
TROUBLESHOOTING
Power System Problems
Table 10.2 describes typical SEL-2020 power system problems and solutions.
Table 10.2: Power System Problems
Symptom Probable Cause Corrective Action
All front-panel LEDs remain dark
when LED TEST button is pressed.
No power to rear-panel
power terminals.
Supply power to rear-
panel power terminals.
Internal power supply
defective.
Remove power and
contact the factory.
+5 Vdc not supplied to pin 1 of
rear-panel communication port(s).
Jumper(s) not installed
on main board.
See the jumper settings in
Section 3: Installation.
Communications Problems
Refer to Table 10.3 for some troubleshooting for typical communications problems.
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