LTPH-UM-1234-01

Appendix C - Ground Faults

 

 

PG-FLEX FAULT ISOLATION

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

1 Verify that the PG-Flex COLU is installed and operational in the CO.

not light

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

Synchronization is being attempted with the upstream unit.

continues to

 

flash green

 

once a

 

second

 

 

 

HDU-409

1 The COLU at the CO is not present or is not operating properly.

loses power

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 25Ω signature of the COLU.

 

 

HDSL line

With PG-Flex the GFD is in the COT line unit. Tip or ring ground faults

power only

between the COT and the doubler causes the power to turn on for a few

appears in

seconds every two minutes. With the HDU-409 doubler, a ground fault after

very short

the doubler on Loop 2 has the same affect. On Loop 1, however, the DC

bursts

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

A grounded pair is being detected by the HDU-409 in Span 2. Remove

shuts off

HDU-409 and check for ground fault in Span 2.

after Span 1

 

comes up

 

 

 

HDU-409 Lists 1, 2, and 3

April 30, 2003

31