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Appendix C - Ground Faults LTPH-UM-1234-01
30 April 30, 2003 HDU-409 Lists 1, 2, and 3
HIGAIN FAULT ISOLATION
Solutions for common problems that may occur with the HDU-409 are listed
in Table 9.
Table 9. Fault Isolation Guide
Problem Solution
LED does
not light
1 Verify that the HLU is installed and operational in the CO.
2 Verify proper cabling between the doubler enclosure and the CO.
3 Measure 100 to 200 Vdc between pins 5 or 6 and 8 or 9. This voltage
peaks every 15 to 30 seconds as the HLU cycles between self test and
line power. If less than 100 Vdc is present, check the cabling or the HLU.
Only the line units mentioned in the “Applications” section can be used
to power doublers (see Table 3 on page 6). Other HLU models may not
provide reliable operation and should not be used.
LED
continues to
flash green
once a
second
Synchronization is being attempted with the upstream unit.
HDU-409
loses power
The HLU at the CO is not present. Measure the resistance of the HDSL input
loop. Resistance should be normal loop resistance plus the 25Ω signature
of the HLU.
HDSL line
power only
appears in
very short
bursts
A grounded pair is being detected by either the HLU or HDU-409 in Span 1.
This causes the unit’s GFD circuit to trigger which forces the HDSL line
voltage off immediately after it cycles on. Remove the HLU and HDU-409
and check for cable ground faults in Span 1. The doubler’s GFD circuit can
easily be checked by grounding any of the loop connectors to the doubler.
This forces the circuit down immediately. If the circuit stays up, either the
GFD circuit is defective or the HDU-409 is not properly grounded.
HDU-409
shuts off
after Span 1
comes up
A grounded pair is being detected by the HDU-409 in Span 2. Remove
HDU-409 and check for ground fault in Span 2.