Hello,
Today I would like to share with you when the fuse of the power supply equipment is damaged, causing the input voltage of the transmission equipment to be abnormal.
System Overview
Four OptiX 2500 devices form a two-way multiplex section protection ring, and the No. 1 network element is the business center point, which is connected to the network management computer.
Failure phenomenon
On a certain day, the service of the network element 3 of the office was interrupted, and the network management could not log in to the network element, and the optical board of the network element 2 and 4 corresponding to the optical board of the network element 3 reported an "R-LOS" alarm.
Fault analysis and troubleshooting
1- From the analysis of the fault phenomenon, it should be the power failure of the 3rd network element;
2- I rushed to NE 3 and found that the rack warning lights and single board indicators of NE 3 were all off. Measure the voltage between -48V and BGND terminal (joint grounding, and BGND and PGND are short-circuited in the transmission cabinet), and it is 0V; measure the output voltage of the power supply device, it is -53.7V, but the power supply device has an abnormal output voltage alarm；
3- It is suspected that there is a short circuit inside the transmission equipment. Turn off the power switch of the cabinet subrack of the No. 3 network element, and re-measure the voltage between the -48V and the BGND terminal, and it is -20.39V. It may be that a local short circuit of the cabinet power box lowers the potential;
4- Turn off the power supply of the power supply device (unplug the power fuse), disconnect the power input cable of the transmission device, and measure the resistance between -48V and BGND when the power switch of the subrack is turned off. The value is several thousand. Ohm, normal;
5- It is suspected that the voltage drop of the power cable is too large. Measure the resistance of the -48V, BGND, and PGND cables. They are all a few tenths of an ohm, which is normal. Further measuring the unplugged power fuse, found that its resistance has reached ten thousand ohms, the cause of the failure lies in the power fuse;
6- Replace with a normal insurance, re-energize the 3rd network element, everything is normal.
Recommendations
The power supply fuse is damaged, but it is not open. Because its resistance value becomes very large, although the output voltage is normal, there is no actual load capacity. Therefore, when the output voltage of the transmission equipment is abnormal, in addition to considering the failure factors of the transmission equipment, the power supply equipment must be checked at the same time.
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