ADC and 3 Doubler - Manual (Page 37)

LTPH-UM-1234-01 Appendix C - Ground Faults
HDU-409 Lists 1, 2, and 3 April 30, 2003 31
PG-F LEX F AULT I SOLATION
Solutions for common problems that may occur with the HDU-409 in
PG-Flex applications are listed in
Table 10 .
Table 10. Fault Isolation Guide for PG-Flex
Problem Solution
LED does
not light 1 Verify that the PG-Flex COLU is installed and operational in the CO.
2 Verify proper cabling between the doubler enclosure and the CO.
3 Measure 150 Vdc between pins 5 or 6 and/or 9 of the HDU. This voltage
peaks every two minutes during the HDSL startup cycle. If less than 100
Vdc is present, check the cabling between the doubler enclosure and
PG-Flex COT shelf. Refer to the COLU practice and verify the COLU is
operating properly.
LED
continues to
flash green
once a
second Synchronization is being attempted with the upstream unit.
HDU-409
loses power 1 The COLU at the CO is not present or is not operating properly.
2 Check the cabling between the doubler housing and the PG-Flex COT
shelf. Measure the resistance of the HDSL input loop. Resistance should
be normal loop resistance plus the 25
Ω signature of the COLU.
HDSL line
power only
appears in
very short
bursts With PG-Flex the GFD is in the COT line unit. Tip or ring ground faults
between the COT and the doubler causes the power to turn on for a few
seconds every two minutes. With the HDU-409 doubler, a ground fault after
the doubler on Loop 2 has the same affect. On Loop 1, however, the DC
power does not shut off because of a ground fault. When there is a ground
fault on Loop 1, the doubler limits its output voltage to approximately -40V.
Pair 2 maintains the normal 130V. This is enough voltage to power the
doubler, but not the RT. Typically the HDSL Loop 1, after the doubler, will
drop the resync periodically. Note that if the pairs are reversed, the polarity
of the voltages are reversed.
Remove the line units and doublers and check for cable faults.
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.