Intermittent vibration, drive bearings going?

[bahngeist]

For the past while a loud(*) medium frequency rumble (best way I can describe it) starts to emanate from one of my systems. Sometimes it occurs after the system has been running for a few days; other times immediately after the SCSI controller spins up the drives (possibly clue 1); and often stops on its own. The front sides of the case vibrate noticeably whenever this rumble occurs (possibly clue 2); and moderate pressure to the sides neither dampens the vibrations nor sound overly much.

* Loud means that it can be heard 6-8 feet outside the room with the door closed; inside the room it completely drowns out the fans (the case is a Lian Li P-60, with a PCP&C Silencer 400 PS, and a Sanyo Denki on the CPU heatsink -- to give an idea of the fan noise being drowned-out). All of the drives (hard and optical) are attached securely; nothing else is touching the drive cages.

For a long time I couldn't localize the problem because I had five drives in the system; one was housed in a 5 !/4 in. bay and inaccessible to touch. I thought the latter was the problem, particularly since the upper drive bay seemed to be the source of the vibrations, and my opticals tested out fine. I have since removed that drive (it was part of a RAID5 array I retired and removed today), and it wasn't the problem. (Anybody interested in a purchasing a now-discounted Mylex AcceleRaid 170 controller and four 18.4, 7.2K lightly used drives

The noise was worse once I booted up the system, and the culprit now seems to be the boot drive, a Cheetah 18XL. On 1st and 2nd boot it vibrated lightly to the touch; and the drive cage seemed to amplify those vibrations appreciably (this would be the cage that sit on the case bottom behind the front fans). What is somewhat perplexing, and clouds the whole issue, is that when I tried to find the source of the trouble before removing the RAID array, the Cheetah was fine. It is also running fine now after two warm boots.

Does the sound and circumstances I described sound vaguely familiar to anyone? If so, how was the problem solved?

 

[P5-133XL]

All drives vibrate, just like all fan's. The fact that you have a loud medium frequency rumble, simply means that your case has a resonance frequency that is a multiple of a high frequency vibration like a fan or a HD in your computer. You can not identify the cause by touch, because it is not the amount of vibration but the frequency of the vibration that matters. With a resonance, the amplitude will grow producing the loud sound you actually hear. The closer the source frequency is to exact multiple of the the case resonance frequency the louder then final sound will be. Please note that the noise that you are hearing does not even necessarily imply that anything has failed.

The easiest way I know of to find the vibration cause is to, without removing the parts, unpower all moving parts (including the power supply) and add power to them one at a time (starting with the PS), with a signifigent time delay, till the noise comes back. You need to keep the components in the case in case because removing them may change the resonance frequency of the case and thus making it impossible to find the source vibration. Any that are not powered at the time the noise re-appears are not the cause.

You should also, re-tighten all screws inside the case (including the MB supports). Make sure the case cover is attached with screws and there are no missing screws. These steps may change the case's resonance frequency. You may also wish to dynamat the case because that will deaden alot of case vibration and will change the case's characteristic resonance frequency.

 

[blakerwry]

great reply mark.

I second checking all screws... sometimes a loose PCI screw or mobo screw/stand-off can be the cause of an anoying vibration.

We all know that a sound card and a mobo don't vibrate by themselvs.. but sometimes other components in our computer cause them to... making for a hard to find, irritating problem.

 

[Cliptin]

On the other hand, I once had a WD IDE drive of around 600MB in size that had intermittant rumbling problems. The bearings eventually failed after about a month and a half of rumbling.

 

[bahngeist]

great reply mark.

I second checking all screws... sometimes a loose PCI screw or mobo screw/stand-off can be the cause of an anoying vibration.

We all know that a sound card and a mobo don't vibrate by themselvs.. but sometimes other components in our computer cause them to... making for a hard to find, irritating problem.

I concur, excellent reply Mark -- thanks a bunch It makes sense particularly since I did change the system by removing the three drives, and that changed the apparent source of the vibrations. I did tighten all the drive screws before closing the case up, and even added a few more where they were needed since I had a 'few' more extra now. The latter may also have added to the issue -- I've addressed resonance issues before (not on computers) and sometimes loosening-off or removing a fastener can solve the problem. I will, however, tighten all the other screws in the case to see if this works.

But all things considered, I will be keeping an 'ear out' on the drive. Cliptin's observations may also be correct (since the sound sometimes does have an off-balance tenor to it).