QRV08 - Humming sound from transformers

[mabu0815]

Hi PA,

I am building the QRV08 and have completed the power supply and regulators now.
All 4 leds light up and the voltages are around 13.8 volts.

So far, so good, but I hear a faint humming sound (I suppose) from the transformers.
It's audible from ca. 50 cm distance from the board.

Have you experienced that before?

The parts I used are the ones from the BOM ordered at distrelec.
The only part that differs is the AD825 which I replaced by AD820 (the AD825 was not available anymore).

After powered up for 1 minute, no part of the circuit gets unusually hot.

Do you have some other expected voltages at certain parts in the regulator circuit I can measure?

Thanks for your help

mabu

[peranders]

Also potted transformers can hum. I have experienced that.