User's Manual

11 Troubleshooting (Fault Finding)
239
11.1.1 Power LED is Off
If the green Powe
r LED does not light up at all, perform the following tests:
1. Remove the power lead from the PIDU and test that the power source (mains or 56 V
battery) is working.
2. If the main or battery power supply is working, open the flap on the left hand side of
the PIDU and remove the RJ45 ODU cable from the PIDU.
3. If the Power LED does not illuminate when the RJ45 ODU cable is removed:
i. Measure the voltage across the +55 V and 0 V pads inside the PIDU flap. An
incorrect reading indicates that the PIDU is short-circuited.
ii. Measure the impedance across the Power connector. An incorrect reading
indicates that the PIDU is short-circuited.
iii. If both of the above tests are successful, it is likely that the PIDU Power LED
is faulty.
4. If the Power LED does illuminate when the RJ45 ODU cable is removed:
i. Remove the jumper (J906) found inside the PIDU flap.
ii. Measure the current with an ammeter placed across the two jumper pins. It
should be 10 mA with the ODU disconnected. An incorrect ammeter reading
indicates that the PIDU is faulty.
5. If all tests so far have succeeded:
i. Reconnect the RJ45 ODU cable to the PIDU.
ii. Measure the current with an ammeter placed across the two jumper pins. It
should be in the range 300 mA to 1 A with the ODU connected.
iii. If the ammeter reading is too high, the ODU may be drawing too much
power, or the ODU may be short-circuited.
iv. If the ammeter reading is too low, the PIDU may be supplying too little power.