Field Notice: FN - 63380 - ASR9000 DC Power Module Replacement Recommended to Prevent Failure of PEM on Lightly Loaded Chassis - Fix on Failure
February 04, 2014
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Updated to remove Upgrade Program section and make minor related changes in all sections
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DC power module might fail during power-on in an Aggregation Services Router (ASR) 9000 chassis that operates under a low-load condition, or it might cause one or more adjacent power modules to fail if one component in the circuit fails. This issue can defeat the redundant power system in the ASR9000 chassis, and result in a single point of failure.
Once a single DC power feed fails, the expected behavior is that the DC power module generates a power feed fail alarm and the power LED starts blinking in order to notify the user to take corrective action. The issue identified here is that the DC power module might take longer or it might not generate a power feed failure alarm or event (%PLATFORM-PWRMON-2-MODULE_FAILURE). Also, the power status LED might remain lit for a failed DC power feed. The power module continues to provide DC power to the router via the other working DC power feed and does not affect router functionality.
Note: The two symptoms described previously are not safety issues.
ASR9000 AC power modules are not affected.
Multiple power modules in a router convert battery power 48V DC to power line cards. Conversion is done by switching the DC power that passes through the Field Effect Transistor (FET) and controls the drive current to FET with a micro-controller at high speed or frequency.
Incorrect FET drive settings in the power module firmware lead to current imbalance in low-load conditions. A low load condition is defined as any one power module sourcing (outputting) less than 10 ampere of current. This output can be determined if you monitor power module output with the use of a system CLI command. The condition is more likely to occur with frequent power cycles.
In order to fix this issue, a new version (-02) of the DC power module has been implemented that includes:
A new version of the power module's internal firmware has been incorporated in order to correct the FET drive setting which led to a current imbalance in low-load condition. The power module firmware change is not field-upgradable.
Design enhancements have been made to the DC power module in order to improve long-term reliability by implementing changes that support the D-share model of load balancing.
The ASR9000 router features two power input feeds (A and B) to each power module. In a few power breaker configurations, the input power feeds (either A or B) to multiple modules that are tied together at a common switch or breaker. If power is disrupted at the breaker to any one feed, the power failure detection and LED circuit do not discharge fast enough, which keeps the LED lit and prevents the power failure alarm.
In order to fix this issue, a new version (-03) of the DC power module has been implemented that includes changes to the-02 version update to fix Issue 1 plus these changes:
Firmware update in order to change the DC PEM parameter setting.
The fix from -02 version to -03 also includes a HW design improvement.
In summary, improvements to address Issue 1 are incorporated with TAN 341-0325-02 and newer versions. Improvements to address Issue 2 are incorporated with TAN 341-0325-03 and newer versions.
One or more DC power module might not provide power to the ASR9000 router on power up.
After a single power feed failure, the %PLATFORM-PWRMON-2-MODULE_WARNING syslog alarm or event might not be generated, and/or the power LED might remain lit. There is no functional impact to the power module or router.
Here is an example of the alarm or event with power feed B disrupted:
All 2KW (TAN:341-0325-01) and 1.5KW (TAN:341-0337-01) DC power modules shipped from February 2009 to January 31st 2011 might be subject to these failures. The replacement program is closed, and Cisco recommends that you replace all -01 versions of these power modules on failure.
For customers with 2KW (TAN:341-0325-02) and 1.5KW (TAN:341-0337-02) DC power modules, Cisco recommends that you take no action at this time and replace only if the problem symptom observed is no power feed failure alarm or a power LED that remains lit for an extended time.
Cisco ships 2KW (TAN:341-0325-03) and 1.5KW (TAN:341-0337-03) versions (or newer) to customers as part of the replacement. Version -02 and Version -03 DC power module can coexist in the same router.
Use the How To Identify Hardware Levels section of this document in order to locate the PID, serial number, and TAN/version of the power module. Use this table in order to identify suspect power module and corrective action.
The HW PID, version/TAN, and serial number can be identified with one of these methods:
- OR -
Note: Deviation is identified only by physical inspection of the label.
A picture of a suspect A9K-2KW-DC power module is shown here. See PID, serial number, TAN, and deviation location in these photographs for A9K-2KW-DC power module (A9K-1.5KW-DC power module is similar, except TAN is 321-0337-01).
Note: A few A9K-2KW-DC power module might be incorrectly labeled as A2K-2KW-DC power module. Use the PID information printed on the faceplate of the PEM and the serial number and TAN from the label.
The PID, serial number, and TAN/version is obtained when you enter the show inventory and show diag commands with administrator privileges.
Here is an example of the show inventory command for the 1.5KW DC power module:
Here is an example of show inventory command for the 2KW DC power module:
Here is an example of the show diagnostic command for the 1.5KW DC power module:
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