Pay attention to TN51XCS Boards MOS Transistors

Summary:
Metal-oxide semiconductor (MOS) transistors in a lot used on TN51XCS boards intended for the Huawei OptiX OSN 8800 have a defect. Because of the defect, the noise introduced by the 12 V power supply on the TN51XCS board is out of range and interferes the signals transmitted over the adjacent high-speed buses. This interference will result in signal degrade (SD). Consequently, bit errors are generated when service boards receive the signals.

[Problem Description]
Trigger conditions:
When the following conditions are met, the issue occurs:
1. A cross-connect board listed in the attachment is used on a network.
2. During deployment or network expansion, slots 6–8, 12–14, 25–27, and 29–31 on the OptiX OSN 8800 I subrack house the following service boards and cross-connections that traverse the cross-connect board are configured on the  Huawei DWDM service boards:
TN55TQX, TN55TDX, TN53NQ2, TN11TOM, TN52TOM, TN11TQM, TN12TQM, TN51THM, TN11LOG, TN12LOG, TN11TQS, TN52TOG, TN11TQX, TN11TDX, TN12TDX, TN52TQX, TN11NS2, TN11NS2T, TN11ND2, TN12ND2-TP, TN12ND2-XFP, TN52ND2-TP, TN52ND2-FP, TN11ND2T, TN12NS2, TN11NS2-B, TN11NS2-AT, TN12NS2T, TN12ND2, TN12ND2T, TN51NQ2, TN52NS2, TN52NS2T, TN52ND2, TN52ND2T, TN52NQ2, TN11NS3, TN52NS3, TN11TSXL, and TN12TMX

Symptom:
1. Concurrent symptoms on the tributary board:
− According to the query of the current performance events, there is bit error second (BES) or background block error ratio (BBER) in the ODUk PM section. In addition, BES and BBER increase, as indicated by multiple queries. When the performance deteriorates, a BUS_ERR alarm is reported.
− According to the query of the performance events on the line board that is interconnected with the tributary board (under the condition that the non-intrusive monitoring in the ODUk PM section of the corresponding channel is enabled), there is no BES or BBER in the section.
2. Symptoms on line boards:
According to the query of the current performance of the line board at downstream site 2 (under the condition that the non-intrusive monitoring in the ODUk PM section of the corresponding channel is enabled), there is BES or BBER in the section and they increase as indicated by multiple queries; however, there is no BES or BBER in the OTUk section on the line board. When the performance deteriorates, a BUS_ERR alarm is reported on the line board that is directly interconnected with the cross-connect board.

Symptoms boards

Identification method:
The issue occurs when the following conditions are met:
1. The bar code of the TN51XCS board is listed in the attachment.
2. If the bar code of the TN51XCS board is not listed in the attachment, confirm that the board was manufactured before February 2011. Users can query the bar code of the cross-connect board on the NMS to check the manufacturing date of the board. For example, bar code 030HYT10B2000005 indicates that the board was manufactured in February 2011 while bar code 030HYT10B100**** indicates that the board was manufactured in January 2011. The last four digits of the bar code indicate the serial number of the board.
3. The issue is confirmed by the inspection script listed in the attachment when the service boards are TN55TQX, TN55TDX, TN53NQ2, or TN52NS3.

[Root Cause]
MOS transistors in a lot used on TN51XCS boards have a defect. Because of the defect, the noise introduced by the 12 V power supply on a TN51XCS board is out of range and interferes the signals transmitted over the adjacent high-speed buses. This interference will result in SD. Consequently, bit errors are generated when service boards receive the signals.

[Impact and Risk]
When the issue occurs, bit errors are generated in services and even services are interrupted.

[Measures and Solutions]
Recovery measures:
None
Workarounds:
Remove the involved service boards and inserted them in other slots to temporarily restore services.
Preventive measures:
Replace the faulty cross-connect board with a cross-connect board whose bar code is not listed in the attachment. For more Huawei transmission equipment please go through www.thunder-link.com

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