What’s the Failure of I-Type PDU Backplane on MA5600T due to Overcurrent

Keywords: MA5600T, Access network

Summary:  If an H801ESCA0 board (BOM number: 03030BYR) of a version earlier than VER.D is installed in the PDU and two channels of external power are input to the PDU, the PDU backplane may be burnt when the two copper plates are poorly connected due to misoperations.

[Problem Description]

Trigger conditions: 1. An I-type PDU (BOM number: 02120328) is used on an MA5600T cabinet. 2. Two channels of external power are input to the PDU. 3. An H801ESCA0 board (BOM number: 03030BYR) of a version earlier than VER.D is installed in the PDU. 4. The RTN copper plate on the PDU is poorly connected. If conditions 1, 2, and 3 are met, this problem will be triggered when condition 4 occurs. The poorer the connection is, the higher the problem occurrence possibility is. Symptom: The PDU backplane is damaged due to overcurrent. The PCB is badly burnt, causing devices inside the cabinet to be powered off. The power is restored only after the PDU is replaced and services are interrupted for a long time. Identification method: Visually check the I-type PDU, especially the copper plates on the PDU. The following figure shows copper plates in good connection status.

 I-type PDU

I-type PDU

The following figure shows copper plates in poor connection status.

copper plates

copper plates

 

[Root Cause]

The I-type PDU supports two external power inputs and four external power inputs. When four channels of power are input to the PDU, the copper plates must be removed. However, when two channels of power are input to the PDU, the copper plates are used to ensure a reliable connection to terminals and cannot be removed. If the RTN copper plate is removed or poorly connected, the input current flows through the H801ESCA board to the negative terminal. In other words, the RTN terminals on the H801ESCA board are short-circuited. As a result, the circuit from the power backplane to the RTN copper plates on the H801ESCA0 board is overcurrent and burnt.

RTN copper plate

RTN copper plate

[Impact and Risk]

Devices inside the cabinet will be powered off. Services will be interrupted and can be restored only after the PDU is replaced.

[Measures and Solutions]

Recovery measures: Replace the I-type PDU and restore power supply promptly. Workarounds: 1. During the installation and deployment of new devices, ensure that the RTN copper plate is properly connected when two channels of power are input to the PDU.

RTN copper plate

RTN copper plate

2. Detail the device installation guide so that the copper plates can be properly connected. To obtain the detailed device installation guide, visit: http://support.huawei.com/support/pages/kbcenter/view/product.do?actionFlag=detailProductSimple&web_doc_ id=SE0000606789&doc_type=ProductManual&doc_type=ProductManual&saveBrowserLoged=true

copper plates

copper plates

Preventive measures: To prevent this problem, the new I-type PDU is optimized in the following aspects: 1. Add a cap for the copper plate screw since March 30, 2013 so that it will not be mistakenly loosened. 2. Upgrade the H801ESCA board to VER.D and replace the RTN copper plate with a diode insulator from September 30, 2013.

H801ESCA board

H801ESCA board

[Warning Expiration]

This warning automatically expires after related conditions are not met.

[Attachment]

None

DSC_3994

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