Installation
150-451-104-02, Revision 02
12
September 18, 1998
HDU-451 List 4
Solutions to Common Problems
This section lists several common problems and describes possible solutions.
If the LEDs do not light:
•
Verify the HLU is installed and operational in the central office. Verify
proper cabling between the Doubler Enclosure and the central office.
•
Measure 100 to 200V dc at the HDU-451 front panel jacks (+/-V). This
voltage peaks every 15 seconds as the HLU powers up. If less than 130V
dc is present, suspect cabling or the HLU. Only the line units equipped
with a high voltage power supply can work with doublers. All such line
units have list numbers that end with a “D” such as the HLU-23I List 6D.
Other HLU versions may sync with the HDU but may not provide
reliable operation and should not be used.
If the HDSL OUT LEDs do not light:
•
Verify that the HRU at the customer site is installed and operational in
the central office. All HRU Remote Units, except List 8, have an HDSL
input signature resistance of 180 kOhms between the Tip and Ring on
each loop. The HDSL input part resistance for the List 8 HRU-4Ds is 10
Ohms.
•
Verify that the central office HLU complies with the second bullet in the
previous problem description.
If the HDSL LEDs flash green continuously:
•
If the OUT LEDs are flashing, verify that the HRU is operational and the
cables between the HDU-451 and HRU are intact.
•
If the IN LEDs are flashing, verify that the HLU is operational and the
cables between the HLU and HDU-451 are intact.
If the HDSL IN LEDs light when the HDSL OUT LEDs flash:
•
No HRU at the remote end. Measure the input resistance of the HDSL
path of the HRU at the HDU-451. The HRU HDSL input has a signature
resistance of 180 kOhms or 10 Ohms between the Tip and Ring on each
loop.
•
Loop resistance or attenuation is out of specification. The loop resistance
should be less than 800 ohms, attenuation should be less that or equal to
35 dB.
