Customer reported that services on OSN 3500 node are interrupted and loop cannot be found on PQ1 ports. It was reported that upon swapping PIU from one slot to another, same problem exists. Further more when the Jack is connected to -48V input of PIU board the breaker of subrack and the main breaker also trips. All the PIUs reported the same issue on site except the online PIU of working subrack which was active.
The node has software 18.104.22.168P01
1. BD_STATUS & POWER_ABNORMAL on PIU.
2. CHIP_FAIL on PQ1
Always check the resistance/continuity test between the two point of -48V input of PIU card after setting the voltmeter to Ohmic/continuity scale.
If a short is found, just replace the board, as it does have small number of internal blocks.
The PIU card has a test point. It has a resistance of OL when it is not faulty. Upon checking the above problem PIU cards they were found short at the two points. Input of -48 on card and GND point.
They lightning protection unit of PIU became short upon a large burst of current. It was observed that grounding was not proper on site.
Keep the grounding of subrack proper. It may cause damage to the expensive and robust equipment like NG SDH upon large burst of current.