Mike's PBX Cookbook

SX-50 Intermittent Night Service Problems


SX 50 systems are intermittently going into Night Service for no apparent reason.

Systems are also reporting A90-001 Alarms (Console Date Errors). And these alarms are coincident with the system going into Night Service.

Frequency can be from a low of once a month to four times a day.


The problem is occurring because very fast rise time noise spikes are being passed through the Power Supply. This noise is corrupting the data signal from the Control Card to the Console. If 3 consecutive error are seen by the system, the system software resets the link causing loss of data from the console and placing the system into Night Service.


Installing a Tripp Lite ISOBAR Surge Suppressor Model IB2-0 has given good results in eliminating noise spikes from reaching the Power Supply. The Trip Lite Isobar should be used in environments where the AC has these fast rise time noise spikes.

ISOBAR is a trademark of Tripp Lite

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