McData Sphereon 4700 Fabric Switch
 

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• Part No: 371-0876-01
• Part Description: Spheron 4700 Power Supply FRU
• Part Min Serial: 609 0001
• Part Max Serial: 622 4489

The McData 4700 power supply's secondary 12V DC circuit can become shorted to ground due to a mechanically induced failure of an insulator caused by burrs on a heat sink.  When this specific issue occurs the power supply's DC output ceases. This issue occurs on the secondary, low voltage side of the supply, with no safety impact and no potential for excessive thermal or current effects within the power supply or to the product in which it is installed.

There are redundant power supplies in the McData 4700 switch, however, there is a secondary issue.  The power control and load sharing circuitry of the 4700 is designed to allow the product to operate with only one of two redundant power supplies.  This specific power supply internal short can result in a secondary system-level outage, but this has never been seen in the field.  This secondary issue may defeat the high availability intent of the dual power supplies.

McData 4700 power supplies manufactured between 2006 week 9 and 2006 week 22 are impacted by this issue.

If this issue occurs, one of two symptoms will result:

1. If a single power supply fails, the switch will continue to operate on the redundant power supply .

2. An intermittent or resistive short in a single supply may result in a system (switch) shutdown.

PEM nuts are installed in the heat sink to secure relevant components. During insertion of a PEM nut as part of the heat sink assembly on the 12-volt rail of the power supply, a ridge was raised as a result of metal displacement on an undetermined percentage of the heat sinks.  In some cases the resulting ridge was pronounced enough to penetrate into the layer of Kapton tape used as insulation between the heat sink and 12-volt components.

Failures analyzed have revealed actual contact between the aluminum heat sink and the active component, causing a short circuit condition.  The cause of the raised metal is attributed to tooling wear at the subcontractor who supplies the heat sink assembly to Cherokee.

Corrective actions implemented by Cherokee as of June 2, 2006 consist of:

1) Factory purge of all heat sinks and rework operation to remove any burr or protrusion cause by PEM installation.

2) In parallel with the heat sink rework operation, Cherokee changed to a thicker Kapton material to provide additional insulation robustness.

Upon failure only replace 371-0876-01 with a 371-0876-01 (or above) outside of the affected serial number range or that has an "R" appended to the end of the serial number.

Identification of Affected Parts (how to):

Affected power supply serial numbers in the following range are impacted:

902534609001 - 9025346224489

An example of a serial number format is 9025346092501, where 609 = week 9 of 2006 and 2501 = power supply sequential number.

Reworked power supplies will have an "R" appended to the end of the serial number.

This issue has been fully evaluated as an FCO, and it has been determined not to meet criteria for an FCO due the extremely low failure rate and redundant power supplies in these switches.

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