Abnormal Sound in Mark V Panel


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We have observed abnormal sound (whistling sound) from Mark V panel (Simplex) which seems to be originating from either R or C core, though its source cannot be identified clearly.

At present no alarms are appearing on Mark V alarm display, diagnostic display and display of LCC cards of both R and C core.
Segment LED display at the DCC card is showing blinking of RED LED at the rate of 0.5 Hz.

Please advise on following.

1. Probable cause/source of this sound.

2. Its effect on turbine operation / Mark V control system.

3. What is the significance of Segment LED left most bit blinking at the rate of 0.5 Hz?

4. How can we eliminate this abnormal sound?

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MKV panels have typically always produced a high frequency sound. Some people can hear it, others cannot. I guess that is age as your high frequency drops off. I wouldn't be too worried about it as you say "no alarms,no diagnostics."

I don't know about the blinking LED, any ideas anyone?
Most power conversion devices contains coils, such as transformers or inductors. These components use electromagnetism to convert AC main power to low-voltage DC power. The varying magnetic fields generated by these components can cause them to physically vibrate at high frequency, resulting in a high-pitched noise.

Usually source of such noise is TCPS (power supply cards) where high voltage is regulated to 5, 15 and 24VDC. Such high pitch sound is of low concern if it is originated from power supply card in <R> or <C> core. 110VDC and other regulated supplies are being monitored and diagnostic alarm appears on low voltage. If there is no diagnostic alarm then you can wait and preemptively replace the noise generating card in next shutdown.
Mark5 Power Supply capacitors (like most electrolytic capacitors) are known to fail, and I have noticed a pitch change over the course of a year or so +/- on some prior to failure that I attributed to the capacitors failing. It could indeed just be a change in the way the inductors are responding to the failing capacitors but every TCPS card sent out had bad capacitors. The failure would not be noticed until the unit was powered down and tried to power back up and would not. Before we migrated to Mark6e, we started sending the TCPS's out for refurb. Well worth the insurance money if you plan to keep the Mark5 system.