Weird Buzzing sound from power supply

Usman Sajid

Honorable
Jul 27, 2013
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I have a Delta Electronics GPS-450aa
I got it from my friend , he used it for few years but its in new condition.
I have a very low wattage pc
Core i5 2400 3.1
2 ram sticks
1 wd hdd @ 7200rpm
1 80mm fan
gtx 750 ti Oced.

So i get a really low frequency buzzing sound for 2 seconds and then it faints and again after 2 seconds.
Even under load there is same buzzing sound , it does not increase nor decrease.
Its not audible unless u put your ear right next to PSU.
Even when computer is off but power supply is getting power there is same buzzing sound.

Is there something to worry about.
Are delta power supply good?
Even if its old but very less used.
 
Power supplies are a pain in the ass.
I just changed the fan on mine (dangerous operation) only to realise that it was one of the capacitors that was "whistling".
I've now mounted it upside down in the case. Behaves.