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The OptiX OSN 7500 Is Irregularly Restarted Because the Power Supply of the Customer's Telecommunication Room Is Faulty

Publication Date:  2012-07-25 Views:  34 Downloads:  0
Issue Description
In an office, the OptiX OSN 3500 is connected to the OptiX OSN 7500 that functions as an extended subrack to converge voice services on the CDMA network in the city. After a period of time, the OptiX OSN 3500 and OptiX OSN 7500 are irregularly restarted at the same time. As a result, all services are interrupted for about five minutes. For the external power supply modes of the OptiX OSN 3500 and OptiX OSN 7500, see the attachment.
Alarm Information
Handling Process

1. Run the :errlog and :mon-get-errlog commands to query the reset records of the NE software and boards of the OptiX OSN 7500 and OptiX OSN 3500. The returns are both TYPE=0xf0000004, indicating that a power-on reset occurs. The power-on reset is caused only by power supply faults. Therefore, The SCC board cannot be faulty.

2. The R&D engineers collect and analyze the data in the black box of the board on the faulty NE. The result shows that the board is normal.

3. Assume that the hardware of the internal power module of the board is faulty. The internal power modules of only one or two boards may be faulty at the same time, and the internal power modules of all the boards cannot be faulty at the same time.

4. Assume that the power supply filter board of the PIU is faulty. The PIUs work in 1+1 hot backup mode and protect a subrack. Thus, on the two faulty subracks on the customer’s network, the four PIUs cannot be faulty at the same time.

5. Assume that the power distribution unit on the top of the cabinet is faulty. As shown in the figure in the attachment, the power modules work in 1+1 backup mode, and the protection mechanism is similar to that of the PIU. Therefore, the power distribution unit on the top of cabinet cannot be faulty.

6. The internal faults of the device are excluded. Therefore, the possible cause is that the input power supply is faulty and the subrack is restarted transiently. If the output power supply is faulty due to a fault on the power distribution cabinet, the corresponding fault may occur on the two subracks. At present, however, the power distribution cabinet of the customer is connected to only the two faulty transmission devices, and thus the possibility cannot be verified from other devices. This possibility, however, is high.

7. During the communication, the customer, however, does not completely recognize our explanations. To verify that the power distribution cabinet of the customer is faulty, we connect an OptiX Metro 1000 to the power distribution cabinet and synchronize the NE time.

8. About one month later, resets occur on the OptiX OSN 7500 and OptiX OSN 3500. In addition, the OptiX Metro 1000 is also reset. Finally, the customer recognizes our assumption that the fault is not caused by our devices.  
Root Cause
According to the fault phenomena, the service interruption is caused by an abnormal board reset. The root causes of board reset, however, are different. Thus, it is necessary to check the device software, device hardware, and external power supply, and consider human factors.
In the case of power supply faults, perform analysis from multiple aspects and fully communicate with the customer to gain customer understanding and cooperation.