'Genius' is being used with increasing sarcasm around my house
May 12, 2008 6:52 AM   Subscribe

My 6-week-old refurb iMac has an intermittent high-pitched whine. Help me guide the Geniuses to a fix.

I bought a refurb 24" iMac in early April. It was the most recent rev at the time (a newer model has come out since).

Since I bought it it has produced an intermittent high-pitched whine. The system doesn't need to be taxed - it can be completely idle with the screen blanked. It's not coming from the speakers, but seems to be coming from the back of the system. Sometimes it will go away if I do anything - just wiggle the mouse - but sometimes not.

The sound is high-pitched and can vary in volume and pitch slightly. It sounds like microphone feedback -not as high-pitched as a CRT whine (which I can also hear). The machine doesn't have to be on for a long time for the sound to occur -it has happened less than an hour after bootup -but it does seem to occur more often when the machine has been on for several hours. I've made sure all peripherals are off, it is definitely coming from the Mac.

I took the machine to the Genius Bar a week ago and described the problem. The Genius thought it was 'CPU whine'. We got a kernel panic when running a load test, so he prescribed a new logic board.

With the new logic board, the sound persists (although it seems less frequent). Additionally, it no longer sees the audio output (neither built-in speakers nor headphones, although USB speakers will work) so they failed in hooking up the new board.

So I've got another appointment with the Geniuses tonight, to get the audio fixed and try to have another spin at this problem. I will ask them (again) to leave the machine on for a few hours and wait until the store is quiet to replicate the sound, but I'm worried they won't be patient enough. A second new logic board seems unlikely to solve the problem to me.

Any idea what would cause this sound? It can be loud enough to wake me from the next room. I'd like to go in there with a specific plan to get the problem solved. Or, is it too soon to ask for a replacement machine with a new serial #? I work in IT and understand the parts in the guts, but hate to do tech support for my own computers on the weekend.

Previously, but doesn't seem to have a solution.
posted by These Premises Are Alarmed to Computers & Internet (9 answers total) 1 user marked this as a favorite

Or, is it too soon to ask for a replacement machine with a new serial #?

I'm pretty sure Apple's policy here is that if you try to get the same problem fixed three times to no avail, you get a new machine. So you might have to have them try another time or two.
posted by DMan at 7:15 AM on May 12, 2008

Whining is most likely the Power Supply or a Fan. If it correlates heavily with disk access, HDD or DVD, then that's the other likely culprit. Lastly the audio components--speakers, etc--may not be grounded.

There aren't any other moving parts, or parts that can really make noise. Have them replace the above one at a time until it stops?
posted by jeffamaphone at 7:55 AM on May 12, 2008

If it is CPU whine, you might want to try QuietMBP - it's a utility for the original MacBookPros which had this problem (mine included).

If that doesn't help, it's probably the fan or hdd, but at least you'll be relatively sure it's not the CPU.
posted by kothar at 8:27 AM on May 12, 2008

I don't know anything about Macs, but my IBM ThinkPad (new in December) made what I would guess is a very similar whine every time it was on battery power for three months. Then, one day, it just stopped. I don't know if it had something to do with breaking in a new high-capacity battery or what, but it did, eventually, go away.
posted by phunniemee at 8:41 AM on May 12, 2008

I've had computers that made a high-pitched whine before. both times, it seemed to be coming from some electrolytic capacitors on the motherboard. I think they were involved in power supply regulation somehow. The thing is, when I first got them, the computers would emit this noise all the time, unless they were under heavy load. I eventually just set them up to run BOINC all the time, and after a while, the noise stopped all together.

I wouldn't know if this even applies to iMacs but it's something to look into.
posted by ArgentCorvid at 9:24 AM on May 12, 2008

I think your best course is to send it back and get another one. I don't see any reason why you should even be trying to fix it.

This is Apple's problem. It shouldn't be your problem.
posted by Class Goat at 12:19 PM on May 12, 2008 [1 favorite]

Try putting setting CPU performance to highest. My old Powermac G5 used to have CPU whine and that fixed it for me.
posted by wongcorgi at 12:27 PM on May 12, 2008

i have an LCD which has a backlight that whines. Since you got the logicboard replaced, and its probably not CPU whine, and hard disks, fans, and cd drives don't whine as much as they "grind" per say (due to cyclical motion) then its most likely the backlight.
posted by evanrodge at 9:46 PM on July 2, 2008

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