Field Notice: FN - 63417 - OTBU 15454-M6-DC: Some M6 chassis DC units are exposed to fuse failure and damage under certain conditions: Replacement Recommended
Published Date December 16, 2011
THIS FIELD NOTICE IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE FIELD NOTICE OR MATERIALS LINKED FROM THE FIELD NOTICE IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS FIELD NOTICE AT ANY TIME.
Initial Public Release
Under certain conditions, the M6 chassis DC unit is exposed to fuse failure and damage. When the input voltage is greater than 55V as measured at the input connector to the node, the 7A fuse of the DC unit may blow open and may also damage the K9 opto-coupler during system power up. This situation results in powering off the related battery on the fan tray unit. The fuse failure also causes the fuse monitoring system to fail, which prevents a failure alarm to be raised on the DC unit.
Additionally, in case of a fuse failure, an M6 chassis alarm is incorrectly generated against the fan-tray assembly (FTA) unit instead of the defective DC unit. This issue is due to a software bug and is fixed in R9.2.1 and R9.3.
Under certain conditions, the M6 chassis DC unit is exposed to fuse failure and damage. The issue is seen when the input voltage is greater than 55V as measured at the input connector to the node. Under these conditions, the 7A fuse of the DC unit may blow open and may also damage the K9 opto-coupler of the DC unit rendering the fuse monitoring system inoperable.
For affected units, an M6 chassis alarm is generated instructing the operator to replace the FTA unit while the DC unit is down, and the DC unit will not recover. In releases 9.2.1 (June 29, 2011) and R9.3, the false alarm will not be raised on the fan tray, and there will be no alarm on the affected DC units.
There is no workaround solution identified for this issue. Customers should check their hardware against the serial number tool provided.
How To Identify Hardware Levels
Customers can compare their hardware serial number against the serial number validation tool provided with this field notice. If the serial number validation tool indicates that the customer's hardware is affected, Cisco recommends replacement of the 15454-M6-DC.
To determine the serial number of your line cards, complete these steps:
- Open Cisco Transport Controller.
- From the Shelf View, choose Inventory.
- On the Inventory tab, locate the line card in question, and compare to the information from the Inventory tab.
- Compare the serial numbers against the serial number validation tool provided.
If you use TL1 commands, complete these steps.
- Run this command to log in:
- Run this command to retrieve the inventory:
- Run this command to log out:
- Compare the information from the TL1 inventory command against the serial number validation tool provided.
A serial number validation tool has been provided so customers can easily check their hardware's serial number to identify affected units.
Serial Number Validation Tool
For More Information
If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:
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