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#24211 - 11/21/12 05:49 AM Hum Query
ryck Offline


Registered: 08/04/09
Loc: Okanagan Valley
I have an intermittent hum that I do not believe is the hard drive but which I would like to know more about, relative to whether it's likely to be a major issue. (iMac 8.1, Intel Core 2 Duo, 2.66 GHz)

Why I don't believe it's the hard drive:

1. The hum is not constant. It comes and goes and sometimes seems to be triggered coincident with a change in the material on screen. Very often, I can get rid of it with a restart.

2. I have booted from my clone and still heard the hum. I assume at this point the Mac hard drive is not running.

3. I have ear-checked. From the front of the machine, the sound originates in the top left corner. Going to the back of the machine, the hum is loudest in that corner and, as I move across the top of the machine toward the centre, the hum diminishes. As well, in the centre I can hear the hard drive whirring - a very different sound.

Questions:

1. If my assumption might be correct (that the hum isn't the hard drive) what is in that corner of the machine that could hum?

2. Is it something I should be able to confirm without a trip to the shop?

3. It is likely to be something that may need immediate replacement or could it be more like my neighbour (a minor irritant I can learn to live with).


Edited by ryck (11/21/12 05:50 AM)
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ryck

iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
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#24219 - 11/21/12 09:25 AM Re: Hum Query [Re: ryck]
alternaut Offline

Moderator

Registered: 08/04/09
Originally Posted By: ryck
1. If my assumption might be correct (that the hum isn't the hard drive) what is in that corner of the machine that could hum?

2. Is it something I should be able to confirm without a trip to the shop?

3. It is likely to be something that may need immediate replacement or could it be more like my neighbour (a minor irritant I can learn to live with).

1. The vibration underlying the hum could be caused by a fan or its resonance, possibly via the heat sink hardware*.
2. If you have a utility that monitors fan speeds, you may be able to correlate hum with certain speed ranges.
3. Answering that is like a crapshoot: youse pays your money, youse takes your chances... wink

*) See step 29-30 of this iFixIt guide. The heat sink is the shiny metal frame angling off to the left, the HD is at the top with its controller board in blue, and the HD fan is underneath the motherboard below the HD.
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#24221 - 11/21/12 12:09 PM Re: Hum Query [Re: alternaut]
ryck Offline


Registered: 08/04/09
Loc: Okanagan Valley
Originally Posted By: alternaut
If you have a utility that monitors fan speeds, you may be able to correlate hum with certain speed ranges.

Good idea. I'll have a look around for one.

Originally Posted By: alternaut
.....that is like a crapshoot: youse pays your money, youse takes your chances... wink

So, I guess I'll be doing my Super Duper backups a little more often than usual....at least until the hum becomes less intermittent and is more easily identified.
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ryck

iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
OS High Sierra 10.13.6
Canon MX710 Printer
Epson Perfection V500 Photo Scanner
Time Machine on 320GB OWC Mercury OTG Pro
Carbon Copy Clone on 500GB OWC Mercury OTG Pro

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#24223 - 11/21/12 02:13 PM Re: Hum Query [Re: ryck]
joemikeb Offline
Moderator

Registered: 08/04/09
Loc: Fort Worth, Texas
Originally Posted By: ryck
Good idea. I'll have a look around for one.

Marcel Bresink's Hardware Monitor is about the most complete I have found and does include fan speeds. Magician Paster that is available from the App Store does not show fan speeds which I believe is what you are wanting to see.
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#24225 - 11/21/12 03:36 PM Re: Hum Query [Re: joemikeb]
ryck Offline


Registered: 08/04/09
Loc: Okanagan Valley
Thanks for the recommendation. I've been to the site and am impressed. You can't get much fairer than an outfit that insists you try the demo before buying to make sure it can do the job you need done.
_________________________
ryck

iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
OS High Sierra 10.13.6
Canon MX710 Printer
Epson Perfection V500 Photo Scanner
Time Machine on 320GB OWC Mercury OTG Pro
Carbon Copy Clone on 500GB OWC Mercury OTG Pro

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#24230 - 11/22/12 01:42 AM Re: Hum Query [Re: ryck]
tacit Offline


Registered: 08/03/09
Loc: Portland, Oregon, USA
If Alternaut's hypothesis about a fan isn't correct, another possibility is that the hum is coming from the inverter that drives the screen's backlight. Go to the Energy Saver control panel and set it to put the display to sleep after 1 minute, then wait for the screen to sleep. Does the hum stop the moment the screen goes blank?
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#24232 - 11/22/12 06:16 AM Re: Hum Query [Re: tacit]
ryck Offline


Registered: 08/04/09
Loc: Okanagan Valley
Originally Posted By: tacit
Go to the Energy Saver control panel and set it to put the display to sleep after 1 minute, then wait for the screen to sleep. Does the hum stop the moment the screen goes blank?

Okay.....I'll do that the next time the hum begins.

However, I can report that the hum will disappear when the screen goes to sleep after logout. As we keep different accounts, our process is to logout and leave the machine in Sleep Mode until the next person logs in.

The machine will continue humming throughout the logout procedure until Sleep is selected and executed. At the moment the machine sleeps, there is silence.

_________________________
ryck

iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
OS High Sierra 10.13.6
Canon MX710 Printer
Epson Perfection V500 Photo Scanner
Time Machine on 320GB OWC Mercury OTG Pro
Carbon Copy Clone on 500GB OWC Mercury OTG Pro

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#24236 - 11/22/12 12:38 PM Re: Hum Query [Re: tacit]
alternaut Offline

Moderator

Registered: 08/04/09
Good point re inverter, which is not infrequently associated with hum. As it happens, the inverter sits underneath the optical drive, to the right of the hard drive, near the top right side of the screen (see step 17-20 of this guide). I figured that the hum might be resonance from a vibrating object, and first considered vibration sources closer to the area where the hum appeared strongest. Hence that fan/heat sink.
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Moderator:  alternaut, dianne, MacManiac