Whistling Computer???

[elf_lord_ZC5]

Hi,

A few days ago my computer started to make a high pitched whine when it was switched off, which would eventually go softer and disappear - initially I thought it was the monitor's high voltage rail oscillating, but found that the sound was coming from my USB headphones, and not as initially thought, the monitor.

What is the likely cause of such behavior?

Is the power supply oscillating, or is it the motherboard, or something else?

Thanks

 

[avid-dreamer]

sounds like some sort of magnetic interference..... unless there's a sexy girl walking past your pc at shutdown that it whistles

 

[Spinx999]

sounds like some sort of magnetic interference..... unless there's a sexy girl walking past your pc at shutdown that it whistles

+ 1 million

 

[elf_lord_ZC5]

sounds like some sort of magnetic interference..... unless there's a sexy girl walking past your pc at shutdown that it whistles

On the fourth floor, not likely

Magnetic interference, again, not likely, but these are USB, so are connected direct to the power rail, via the USB port. Audio section/rail should be dead when PC shutdown. So either there is noise from some unknown source on the power rail, or the DA converter/audio card, in the headphones themselves is faulty - way I see it.

What puzzles me, is that if you switch on the PC again, it goes away ...

 

[MickeyD]

Faulty sound port?

 

[avid-dreamer]

Have you tried different usb ports? Usb ports still have some power going through them when switched off maybe that low power is making the headphones go bonkers, probably the headfone coils are damaged causing unwanted vibration at low power making it whistle like that.

 

[Sik]

usually a problem with earthing, also might be a faulty power supply...
Is the PC on a UPS?

 

[antowan]

Check the front panel plugs for the USB ports on the motherboard.

 

[elf_lord_ZC5]

Faulty sound port?

Plugged into one of the rear USB ports.

 

[elf_lord_ZC5]

Plugged the headset into the USB port furthest from the monitor cable and network cable, and it is quiet, is also quiet connected to the front USB ports.

So my only conclusion is that the headset cable is not properly shielded.

But that should not matter as both the monitor cable and network cable should not cause EMF interference.

Will monitor over the next few days, and see if it starts up again. Then I might have to start considering the power supply, or earthing problems. The back plate on the case makes the USB ports a tight fit ... ???