Mysterious Ticking Noise?

[ryan.stewie]

I dont know how long this has been going on for but ive just noticed it. ONLY when the display sleeps, the upper left hand side of my 24" imac makes light ticking noises once every few seconds (its very light ticks, theyre hard to hear unless you put your ear to the computer). It doesnt occur when the screen is on and when everything is on, and it doesnt occur when the computer sleeps, it only happens when I put the display to sleep, which seems weird. I don't think its the HDD, I've checked the SMART status and all is fine, I've also checked the console. Why is this ticking noise occurring when the display sleeps and no time else and what is making it?

EDIT: Also, if the iSight camera is on and the display sleeps, the ticking noise doesn't occur.

 

[Blue Sun]

I too experience this.
It seems to be the power supply. I don't think there is any fix other than getting the PSU replaced.

 

[geoffreak]

There's a bomb in your iMac and it is counting down.
But seriously, just go have it looked at at the Apple store.