Johnson Controls 300 Series Manual page 101

Network Control Module 300 Series Technical Bulletin
Power Supply (NCM3XX)
Periodic inspection is required to ensure the NCM power supplies are
performing at their peak. This section describes routine power supply
inspection.
Remove the power supply cover to complete the inspection. Replace
the power supply if any of the following conditions are detected:
• Power Supply Visual Inspection
- The Metal Oxide Varistors (MOVs) are discolored. The MOVs
are the power line transient suppressors (located on the power
conditioning board) - large red discs about the size of a nickel.
If the MOVs are discolored and not bright red, the supply must
be replaced. If the MOVs are discolored, future transient
suppression may not happen.
- The power supply printed wiring board has any discoloration
spots or brown areas.
• Power Supply Touch
The power supply should be cool/warm to the touch.
• Power Supply Smell
Replace the power supply if it smells burnt.
Determining the Status of the Power Supply
This procedure is optional. It can help determine whether the power
supply is defective.
!
IMPORTANT: When probing the ISA slots, avoid short circuiting the
power pins to the adjacent ISA pins (3, 5, 7, and 9). Short circuiting the pins
may damage the main board.
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