Do I need a new computer power supply, or can I fix this one?
September 6, 2013 3:18 PM   Subscribe

I have a 650W power supply in my computer that I installed myself back when I asked this question (scroll through the answers on that for most system specs). This morning, the fan on the power supply started making noise. Do I need to replace the supply entirely, or is this something I can fix on my own?

Since I didn't list it previously, I have a 650W Cooler Master power supply. This morning, my computer started making what was obviously a fan noise, like sticking a baseball card in your bike wheel spokes kind of thing. Turning my computer on its side makes the noise almost completely go away. I took apart the computer and gave everything inside a good blow with compressed air, but the noise persists. I've DEFINITELY narrowed it down to the power supply - I've removed it and turned the computer on, which starts the fan; the noise occurs whenever the power supply's orientation is returned to what would be "upright" within the computer. There don't look to be any obstructions entering the fan path from within or without the power supply (since I've removed it from the casing, but still left the cables attached, and it still makes the noise, it's quite obviously something within the supply). It seems the fan blade itself is just riding lower than it used to, so the center is now resting on the grille at the bottom of the supply housing, so the blades hit the grille when turned upright. Is there a way to keep the fan riding high instead of dropping down again? There are high voltage warnings all over the exterior of the power supply, and it looks like I'd have to remove the whole cover to get to the fan, so is this something I can fix myself? The thing only cost about $80 - should I just get a new one?
posted by LionIndex to Computers & Internet (10 answers total)
 
As I recently observed, the thing about flipping a switch or breaker on line voltage is that it brings tremendous clarity to the "Does my idea of how this thing work match how it actually works?"

That was for house wiring, but some of the same things apply here. There's no magic: Unplug it. Press the power button on your computer to try to start it, in order to drain any capacitors in it. Open it up, replace the fan (may require soldering(!)), close it back up.

The difference is that the power supply contains high voltage connections, so if you get something wrong you can get serious smoke and sparks. But a fan change is not a difficult procedure, especially if that fan connector is socketed rather than soldered (I haven't been inside a power supply recently), and as long as you don't leave loose screws inside it or anything you should be fine.
posted by straw at 3:24 PM on September 6, 2013


I'd consider fixing it yourself if:

(1) you can get to the fan easily without having to disassemble anything but the case of the PSU
(2) you can easily disconnect the fan's power itself (which is often connected to the PSU's board just like case fans are connected to the motherboard)

I'd stay away from disassembling the PSU's guts and even more so from messing around in there with a soldering iron unless you have experience with doing that kind of stuff.

Anyhow, if you can get the fan out and find a replacement with the same specs/size (which should be no problem, most fans are widely available standard sizes) then you'll save yourself a lot of money. A replacement fan should only cost a few bucks, a high end one that's really quiet with long lasting bearings maybe $8-12 depending on size.

I've replaced PSU fans successfully before and it wasn't particularly painful.
posted by Hairy Lobster at 3:26 PM on September 6, 2013 [1 favorite]


Also: what straw said with regards to draining capacitors first!!!!
posted by Hairy Lobster at 3:27 PM on September 6, 2013 [1 favorite]


Leave it unplugged overnight before opening it. Turning off the switch is not sufficient, it must be disconnected from the wall.

You will want to leave it overnight to be sure the filter capacitors are drained. Pressing the power button to drain the caps, as suggested upthread, won't do it. The caps you want to drain are in the power factor correction circuit, not the DC output rails. The power factor filter caps are probably charged to 350-400V, so do not mess around.

It is not unheard of for manufacturers to omit the bleed resistor in these capacitors, in which case it is possible they will still carry a high charge days later (e.g. Apple Time Capsule original version). Be careful and avoid poking around inside unnecessarily.
posted by ryanrs at 3:33 PM on September 6, 2013 [4 favorites]


My case fans recently started to make a rattling, grinding noise, and it turned out the fan bearings needed oiling. Some 3-in-1 white lithium lubricant fixed it up.

I've heard this to be the case for other types of fans too, not just case fans. If you can detach the power supply safely per the advice above, giving the fan a bit of lubricant might be worth a try.
posted by Zelos at 4:33 PM on September 6, 2013


Definitely fixable, if you can do it safely. The fan will probably be unpluggable inside the PSU, and then you could swap it out for another same-size fan (easy to find on a site like Newegg or such) or else attempt to get at the bearing and relubricate it with a bit of mineral oil. Usually the bearing can be lubed by just peeling off the sticker in the middle of the fan, possibly removing a little cap, and then dripping a few drops of mineral oil (which you may already have if you have a sewing machine or an electric hair clipper) onto the bearing and sealing it all back up. See this old but still relevant article for more details.

Do be safe, though. As others above have mentioned, PSUs do have beefy capacitors in them that can deliver a dangerous shock even if turned off. This is not impossible to deal with but you do need to be careful. In addition to letting the computer sit unplugged overnight, I would work inside the PSU wearing rubber gloves and with only one hand (so that any shock would be less likely to travel across my chest). The first thing I would do upon opening it would be to remove the fan and work on it somewhere away from the PSU. I have been bitten by the capacitors in a PSU before, and it was no fun. I was lucky that all I got was a bite, instead of something more serious.

That said, I would not hesitate to do this myself if I had your problem. Do it, but be careful.
posted by Scientist at 6:11 PM on September 6, 2013


Also, pay attention to what type of bearing is in the fan you use to replace it. According to this fans with sleeve bearings should be mounted vertically but orientation doesn't matter for ball bearings.

That site is also a fantastic resource for selecting a specific fan (and some other oft overlooked components).
posted by VTX at 8:22 PM on September 6, 2013


Usually the bearing can be lubed by just peeling off the sticker in the middle of the fan, possibly removing a little cap, and then dripping a few drops of mineral oil (which you may already have if you have a sewing machine or an electric hair clipper) onto the bearing and sealing it all back up.

Mostly agreed, except that all you'll need is one drop of light oil. 3-in-1 or sewing machine oil are good. Engine oil is too heavy. WD-40 isn't oil.

If you lube a computer fan with more than one drop of oil, you fairly rapidly get oil seeping into the sticker adhesive, which will give way after a week or so and then let oil creep slowly all over the surface of the fan blades, and this makes them get filthy with hard-to-remove dust buildup.

A drop of light oil will typically quieten a rattly computer fan for about two years.

There might be parts inside a computer PSU that retain the ability to deliver a painful (but not usually life threatening) electric shock for some hours after the mains has been disconnected, so try not to touch anything inside the PSU case but the plug that connects the fan to the PSU circuit board. If the fan wires are soldered to the board rather than plugged in, oiling the fan will be a little fiddlier but should still be quite do-able as long as you pay attention to not touching anything else.
posted by flabdablet at 9:51 AM on September 7, 2013


A few things of note, I've done this 4-5 times over the years. Including with a really high end power supply I had to track down a special fan for.

First, google the model number of the fan when you pull it out. You want to get one with close to or the same CFM rating if not just the identical fan. If you don't care about noise and it wasn't a ball bearing fan, now is the time to get one because they last forever(seriously though. A friend is still using a power supply I bought like ten years ago that has one)

Second, check right after you reassemble the whole shebang that the fan actually spins when you first start the thing. Some power supplies start at, or drop to a low voltage for the fan after a few seconds. Some fans have higher minimum start voltages than others. If you can get this info from the stock fan via google and compare it to your replacement fan that's great.

Third, if the old fan was soldered in just cut the wires, strip them, and heat shrink tube them to the wires for the new fan. Don't bother with soldering, this isn't some massive high current line. I've even just electrical taped them before when I didn't give a fuck. Just make sure there isn't tons of excess wire that could get caught in the fan or lay on anything that gets hot.

The rest has been coveted adequately, but the CFM thing especially is quite important. Some fans are quiet at low speeds but can move immense air at full power. Some PSUs depend on being able to scale up the air moving through really intensely at times, in hot rooms, etc.
posted by emptythought at 12:47 PM on September 7, 2013


Thanks, all. I think mucking around with the interior of the PSU looks like more than I want to deal with, so I'll probably just end up getting an entirely new unit and not worry about it.

Otherwise, I'm fairly certain that the problem is more of a "fan blades hitting the housing" problem more than a "grindy bearings" problem, so unless adding oil will somehow suck the fan back up toward the motor, I really don't see how that will fix anything here.
posted by LionIndex at 4:54 PM on September 8, 2013


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