PMU Board Reports PWR_MAJ_ALM Due to Unfavorable Power Supply Environment

The PMU board reports a PWR_MAJ_ALM alarm due to unfavorable power supply environment.

Product

OptiX Metro 6100, OSN6800,OSN8800

Fault Type

Power Supply

PWR_MAJ_ALM

Symptom

When commissioning a network, field engineers find that the T2000 indicates that the input voltage of an OptiX Metro 6100 NE is excessively high (reaches -79.6 V). In this case, the PMU board reports a PWR_MAJ_ALM alarm to the T2000. However, after measuring the input voltage by using a voltmeter, the field engineers find that the input voltage is within the normal range (the measured voltage is -53 V).

Cause Analysis

The possible causes of this problem are as follows:

• The PMU board is faulty.
• The power supply environment is unfavorable.

Procedure

1. Replace the PMU board. The problem persists.
2. Measure the input voltage by using a broadband oscilloscope, finding that the input voltage (-53 V) contains high frequencies with the amplitude up to 80 V. Thus, the PMU board cannot identify the input voltage. As a result, the PMU board works abnormally and reports a PWR_MAJ_ALM alarm.

Result

The problem is resolved.

Reference Information

None.

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