August 20, 1997
AXIS - The problem is only on the new layout of the backplane (assembly 218412-00). The earlier version (assembly 218880-00) does not have this problem.
AXIS fans show below normal tach reading. After entering a dspshelfalm command, one or more fans may show an rpm value that is below normal; usually this value is 0. However, the fan appears to be spinning normally.
The problem is caused by a layout error. There are vias which may short to chassis ground when the cabinet is assembled. These vias can be seen on the solder side of the backplane near the connectors PSA, PSB and J17. For a complete list of signals that may short to chassis ground, see the document AXIS via (PEM) Signals Which May Short to Chassis Ground.
Fans 1, 2, 3, 5, or 6 show below normal speeds (this may happen on any subset of these). This anomaly is associated with assembly 218412-00 that shipped between December 1996 and June 1997.
The fans are working in this condition, however minor alarms are generated and cannot be disabled.
Replace the AXIS and Fan Assembly with either the AXIS assembly 218412-00 that shipped under a deviation after June 1997 or the RCN: R97-2790 assembly. This will resolve the minor alarms.
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