Mac Pro 8-core Power Supply Making Noise Like Refrigerator Radiator

[kamek]

This is in reference to a Mac Pro 3,1 8-core purchased around Feb 2008.

Lately, I've noticed a strange noise coming from my power supply that sounds like the noise a refrigerator radiator makes. It's a humming noise that rapidly comes and goes, constantly.

The power supply fan speed was running at 599rpm yesterday, but is running at 629rpm today.

I'm not sure if the problem could've been caused by adding additional ram (12GB, OWC) or an additional HDD (3rd HDD, WD), but I didn't really notice the noise until after adding these components.

What could be the cause of this problem? What are my repair options if necessary (without Apple Care)?

Thanks in advance. :confused:

[Infrared]

The power supply fan speed was running at 599rpm yesterday, but is running at 629rpm today.

The power supply fan speed varies in relation to the ambient temperature.

[akadmon]

It's most likely one of the hard disks resonating. Try swapping bays.

[kamek]

It's most likely one of the hard disks resonating. Try swapping bays.

I'll give this a try when I get home in the afternoon. Would it be ok to move the HDD from bay 3 to bay 4 and leave bay 3 open?

[goodcow]

I'll give this a try when I get home in the afternoon. Would it be ok to move the HDD from bay 3 to bay 4 and leave bay 3 open?

Yes.

[kellen]

I had the same problem and it eventually went away though. Researching it I found the door may be the problem, try reseating it or leaving a combination of the latch open/closed and with the lock mechanism out.

I also was told to try upping that fan rpm to 600, as users reported it making that sound disappear.

What would make mine go away was moving the computer. It would go away for a little bit, but return intermittently.

Like I said mine has disappeared. Seemed to work itself out.

[kamek]

I had the same problem and it eventually went away though. Researching it I found the door may be the problem, try reseating it or leaving a combination of the latch open/closed and with the lock mechanism out.

I also was told to try upping that fan rpm to 600, as users reported it making that sound disappear.

What would make mine go away was moving the computer. It would go away for a little bit, but return intermittently.

Like I said mine has disappeared. Seemed to work itself out.

I tried removing the door, which only led to making the noise more audible. My power supply fan speed has been running between 599 to 629 on its own. I also did move the computer (thinking it was too close to the wall), and the sound did go away for a few minutes, but it came back! Thanks for the suggestions - you're lucky the sound went away on your Mac!

I'll update once I get to move the HDD around.

[kamek]

Tried swapping HDD bays and the sound is still there.

I'm just about positive that the humming noise that comes and goes every second is coming from the power supply.

Any other suggestions?

[nanofrog]

Tried swapping HDD bays and the sound is still there.

I'm just about positive that the humming noise that comes and goes every second is coming from the power supply.

Any other suggestions?
Assuming there's no issues with the PSU itself, it could be "dirty power" (noise, brown-outs = low wall voltage, but not a total loss of power,...). A good UPS could help, but you'd need to pick one up in order to test it (presuming you don't have one that you can borrow, and the consumer units aren't the best for testing this, as more noise can get through). You'd want an APC SmartUPS or similar - continuous unit, not a switched unit (power always comes off the battery, not the wall and switched to the battery in low voltage conditions).

[kamek]

Assuming there's no issues with the PSU itself, it could be "dirty power" (noise, brown-outs = low wall voltage, but not a total loss of power,...). A good UPS could help, but you'd need to pick one up in order to test it (presuming you don't have one that you can borrow, and the consumer units aren't the best for testing this, as more noise can get through). You'd want an APC SmartUPS or similar - continuous unit, not a switched unit (power always comes off the battery, not the wall and switched to the battery in low voltage conditions).

But the computer still runs just fine, except the power supply makes a hum now. Can you give some more insight on the "dirty power?"

[nanofrog]

But the computer still runs just fine, except the power supply makes a hum now. Can you give some more insight on the "dirty power?"
Noise and poor power conditions (voltages all over the place, and likely low). Filtration is needed, and a good UPS can provide it (handles more than filtration, as it can deal with outages and low voltage scenarios = brown-outs). You could even benefit by looking at the other devices on the same circuit. Assuming there's something else on it, try unplugging those devices, and see if it changes the hum in the PSU (it could get lower, and better yet, vanish <inaudible>).

Ultimately, wall voltages aren't constant as they will vary with the load on the circuit you're connected to. For example, if you're at the end of a run (physical location of your house/apt/office), the power isn't as clean and stable as it is nearer the beginning of the circuit (power lines and transformers all the way back to the power plant). Age and condition of the equipment even matters, especially if it's not well maintained..

[kamek]

Noise and poor power conditions (voltages all over the place, and likely low). Filtration is needed, and a good UPS can provide it (handles more than filtration, as it can deal with outages and low voltage scenarios = brown-outs). You could even benefit by looking at the other devices on the same circuit. Assuming there's something else on it, try unplugging those devices, and see if it changes the hum in the PSU (it could get lower, and better yet, vanish <inaudible>).

Ultimately, wall voltages aren't constant as they will vary with the load on the circuit you're connected to. For example, if you're at the end of a run (physical location of your house/apt/office), the power isn't as clean and stable as it is nearer the beginning of the circuit (power lines and transformers all the way back to the power plant). Age and condition of the equipment even matters, especially if it's not well maintained..

Haven't had the chance to try out a UPS yet, but the noise seems to have calmed down a little after removing my third HDD. Could it be that I'm loading the power supply with too much? Here are my specs that were added from the stock configuration:

- 6 x 2 GB OWC ram
- 1 x 750 GB Samsung Spinpoint F1 HDD
- 1 x 1 TB WD Caviar Black HDD

[handheldgames]

If its not a new machine, try cleaning it with compressed air. Blow from the inside to the out. Take your machine outside for this one.

If its under warranty, take it in. If the capacitors or fan are humming, could be a sign of impending failure.

[Spacedust]

Replace the rear fan in memory compartment. I got the same sound in Mac Pro 2006. After replacement it's gone ;)

[nanofrog]

Haven't had the chance to try out a UPS yet, but the noise seems to have calmed down a little after removing my third HDD. Could it be that I'm loading the power supply with too much? Here are my specs that were added from the stock configuration:

- 6 x 2 GB OWC ram
- 1 x 750 GB Samsung Spinpoint F1 HDD
- 1 x 1 TB WD Caviar Black HDD
No, that's not much of a load (adds ~80 - 85W), so there's nothing to worry about in this area. :)

[kamek]

If its not a new machine, try cleaning it with compressed air. Blow from the inside to the out. Take your machine outside for this one.

If its under warranty, take it in. If the capacitors or fan are humming, could be a sign of impending failure.

I don't believe it's under warranty anymore because I purchased it around Feb 2008. Do you suggest I give Apple a call to see if they're still willing to help me? Should I just purchase the Apple Care plan even though I would only have 1 remaining year on it? I'm not sure how all this works.

Replace the rear fan in memory compartment. I got the same sound in Mac Pro 2006. After replacement it's gone ;)

The hum is pretty loud from the lower fan by the memory now that you mention it. Either that, or this hum has driven my crazy...

[akadmon]

You can't buy Apple Care for a machine that's more than 1 year old.

[kamek]

Still looking for suggestions, please!

[nanofrog]

Still looking for suggestions, please!
What happened with the UPS, moving items off the circuits,...?

Without such information, there's no real way to help you.

[bearcatrp]

Install smcfancontrol. then adjust each fan by itself to isolate which fan is giving you a problem. It won't adjust the PSU fan though. You might want to insure they are tightened down. If it is the fan, its not hard to replace it yourself.

[kamek]

What happened with the UPS, moving items off the circuits,...?

Without such information, there's no real way to help you.

I've tried taking the load off the circuits with no luck. I don't have a readily available UPS, and I would end up having to buy one.

Install smcfancontrol. then adjust each fan by itself to isolate which fan is giving you a problem. It won't adjust the PSU fan though. You might want to insure they are tightened down. If it is the fan, its not hard to replace it yourself.

Thanks -- I'll looking into smcfancontrol. I'm not sure if it's a fan because it almost sounds as if the electricity through the PSU is causing the sound.

[nanofrog]

I've tried taking the load off the circuits with no luck. I don't have a readily available UPS, and I would end up having to buy one.
You need to try this then, and see what happens (if it's a power quality issue or PSU).

[drtech]

I think @spacedust may have located the issue. We run many (many) workstations and servers (including Mac Pros) and eventually the bearings in the fans will go bad. It starts with with an ever-so-slight vibration, then a hum, then eventually a "grinding" noise (although it's not actually grinding but rather resonance in the bearings). Replacing the fan works like a charm.

The higher fan RPM may actually be a symptom of the bad bearings. The bad bearings cause more drag in the fan thereby causing the Mac to increase the power to the fan to maintain RPM.

Fans are relatively inexpensive. You may want to consider giving this a shot before tearing apart the entire Mac chasing the sound.

Jeff

[nanofrog]

I think @spacedust may have located the issue. We run many (many) workstations and servers (including Mac Pros) and eventually the bearings in the fans will go bad. It starts with with an ever-so-slight vibration, then a hum, then eventually a "grinding" noise (although it's not actually grinding but rather resonance in the bearings). Replacing the fan works like a charm.

The higher fan RPM may actually be a symptom of the bad bearings. The bad bearings cause more drag in the fan thereby causing the Mac to increase the power to the fan to maintain RPM.

Fans are relatively inexpensive. You may want to consider giving this a shot before tearing apart the entire Mac chasing the sound.

Jeff
The OP still hasn't sorted out power as a possibility though, and it's easier than tearing into the PSU to swap out the fan. ;)

[sparkie7]

put a can of coke inside. might stop the noise

sorry couldn't resist :D

[kamek]

I think Spacefrog is right with the exhaust fan. I ran smcfancontrol as bearcatrp suggested and the sound goes away when I speed up the exhaust fan. Looks like this is what I'll be replacing!

[kamek]

Update: So now my 3rd HDD is back in and it really seems as if the noise is coming from the PSU. I sped up the exhaust fan and took the panel off to listen, and it was not coming from there. After taking a closer listen to the PSU, the hum is definitely coming from there, and it also sounds as if the fan is grinding inside. Does this mean the fan is causing all the noise? How would I go about troubleshooting this or even replacing it?

[nanofrog]

Update: So now my 3rd HDD is back in and it really seems as if the noise is coming from the PSU. I sped up the exhaust fan and took the panel off to listen, and it was not coming from there. After taking a closer listen to the PSU, the hum is definitely coming from there, and it also sounds as if the fan is grinding inside. Does this mean the fan is causing all the noise? How would I go about troubleshooting this or even replacing it?
Pull the PSU from the system, and open it up. Carefully, as you don't want to touch the capacitors (they will still have a charge, and can zap you). Remove the fan and replace it. You may be able to unplug it, or you may have to use some other means (desolder/solder in a new one, cut & splice wires via soldering + heatshrink tubing, crimp connectors, or even wire nuts) assuming it's soldered to the board.

I've not been inside a MP's PSU, so I don't know how the fan's wiring is connected. But overall, it shouldn't be that difficult. :)

[bearcatrp]

Unless smcfancontrol has been updated, it never was able to spin up the PSU fan. If it does, can you tell me what version your using so I can check mine again?

[itou]

vacuum the inside of it. the fans might get stuck with lint and dust.