How do you replace a power supply fan?

[Lemon law]

A few days ago my wife's very reliable computer suddenly made a little fan rev up noise followed by dead silence as the power supply fan suddenly died--seemingly dead.

The computer still runs rock solid but I notice the auxilary sensor now shows 53 C---when it ran much cooler before. And my sensor alos shows only 8.5 volts on the 12 volt rail---something it was doing long before the fan crapped out.

I can remove the power supply from the case---but its not immediately obvious how I take it apart so I can replace the fan. Or would I be better off replacing the entire power supply?
Or should I just run it until it drops.---the cpu and mobo stay around 35 C.

And if I replace the power supply---what brands are good and how many watts do I need.
Audio and video are on the mobo---and she is pulling one HD, 2 cd drives, and one floppy drive.---and since the computer is pretty old---only a athlon XP 2400---I am loathe to invest much in it.

 

[mechBgon]

The system is in serious danger if the 12V rail is at 8.5V. Don't run it like that or you may harm your HDD.

Best course of action: replace the PSU with a good-quality new one if the computer doesn't require some oddball style of PSU.

1) does your motherboard use a ATX12V cable, yes/no?

 

[mechBgon]

BTW here is my blanket nominee for her system, assuming it takes normal form-factor ATX power supplies:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817104931

Key point for AthlonXP motherboards: it has a healthy 3.3V+5V combined rating of 220W maximum. Nowdays this isn't important because CPUs and GPUs pull mostly 12-volt power, but for most AthlonXP boards it was significant. It has a 20-pin main plug, and is a respected brand but not insanely expensive. 12cm fan should run pretty quiet.

 

[KGB]

Originally posted by: Lemon law
A few days ago my wife's very reliable computer suddenly made a little fan rev up noise followed by dead silence as the power supply fan suddenly died--seemingly dead.

The computer still runs rock solid but I notice the auxilary sensor now shows 53 C---when it ran much cooler before. And my sensor alos shows only 8.5 volts on the 12 volt rail---something it was doing long before the fan crapped out.

I can remove the power supply from the case---but its not immediately obvious how I take it apart so I can replace the fan. Or would I be better off replacing the entire power supply?
Or should I just run it until it drops.---the cpu and mobo stay around 35 C.

And if I replace the power supply---what brands are good and how many watts do I need.
Audio and video are on the mobo---and she is pulling one HD, 2 cd drives, and one floppy drive.---and since the computer is pretty old---only a athlon XP 2400---I am loathe to invest much in it.

If you are willing to spend about 15 minutes and 5-10 bucks for a new fan, they are very easy to replace.

But definitely do not run it without a fan "until it drops".

 

[Lemon law]

I do know from the asus a7s266vm-u2 mobo manual that its takes a 20 pin atx connector. And I will use a vom to see if the sensor is correct or if the sensor lies. And you are saying to check the hard drive connector. But thanks for the info mechBgon. And quiet is a real criteria for us.

 

[John]

I don't think your pc would be running stable if the +12v was @ 8.5v If you want to replace the fan you can remove the power suplpy top cover, remove and measure the fan (80, 92, 120mm are common sizes), snip the fan wires, install the new one, snip the connector off the new fan and tie it into the fan leads, then use some heatshrink or electrical tape to cover the leads. It seems easy enough, right?

 

[cubby1223]

At that point, I just invest in a whole new power supply. Good ones are cheap enough these days. Like one of these:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817104039

Or for an Athlon XP, a single 12v rail psu might be better:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817103485

If you're getting erratic readings like that, it's probably best to replace the psu and see if the sensors are off.

 

[John]

<edited> I just noticed Lemon said he was going to use a DMM to test the rails. :thumbsup:

 

[KGB]

Originally posted by: John
I don't think your pc would be running stable if the +12v was @ 8.5v If you want to replace the fan you can remove the power suplpy top cover, remove and measure the fan (80, 92, 120mm are common sizes), snip the fan wires, install the new one, snip the connector off the new fan and tie it into the fan leads, then use some heatshrink or electrical tape to cover the leads. It seems easy enough, right?

John,

I've found it easier to just snip the old leads flush with the PCB and thread the new fan wires OUTSIDE the PSU housing and connect it to an unused Molex connector.

 

[cubby1223]

BTW, I've got one of these testers, and it's literally worth it's weight in gold:
http://www.newegg.com/Product/Product.aspx?Item=N82E16899887004

 

[Alone]

Turn off the computer and unplug it. Leave the PSU attached to the 20/24pin and try to power it on. This should discharge the capacitors.

Now unplug the PSU, open it up, TOUCH NOTHING, but clip the two fan wires on the board. Unscrew the fan and take it out, put in a new one, and thread the wires out the side of the psu housing and attach it via molex or 3/4 pin, like I did.

 

[Lemon law]

Well a few mysteries now solved---I finally got my wife pried off the computer and a VOM plugged into a spare molex connector--and the the sensors that feed my monitoring program,
in this case everest 2.2, are telling the fib---as I get over 12.2 volts from yellow to ground and better than 5.2 volts on red to black. And this while the computer is powered up and running so its a loaded voltage that presumably will not drop because I am reading an already under load voltage.

So I will check the local computer shop for a replacement power supply fan. Leaving me still clueless on how to remove the power supply cover. But the fan exhausts through the back of the power supply---and four screws on the back of the power supply removes the power supply from the computer case.---but that gives me zero access to the fan because its screwed into the back plate with another four screws that don't give me access to the fan itself as the backplate itself appears unremovable. I see another four screws on the bottom of the power supply---are those the ones to remove? Once I can get access to the front and back of the fan, I can handle the wire snipping and splicing---but have never taken a power supply apart before which is why I ask.

 

[John]

Originally posted by: Lemon law
I see another four screws on the bottom of the power supply---are those the ones to remove?

Yes

 

[ronach]

It appears you havn't done much tinkering with hardware before, no problem tho. Get yourself a muffin tin or the like with multiple areas for screw and hardware placement as you disassemble the PSU. Put all screws from one section in a seperate container in sequence, so when you get around to assembling the unit, you can just do everything in reverse..if you have any extra screws...well....stop and take a good look around before proceeding and leave it out. Some people like to put numbered masking tape pieces on sections as they take things apart, that works. Most guys and gals here can take things apart without doing this stuff...shame..hee. Just think your project over carefully..have the right tools handy..tape the kids up..put the dog and cat outside..do this with your signifcant other at your own peril..hee. Most of all..have fun. Cheap to.

 

[jackschmittusa]

The 4 small screws will remove the cover. There is often a sticker that spans the 2 cover pieces that needs to be cut. Four screws remove the fan. These are all of the screws that need to be removed, and the 2 sets are quite different, so I doubt anyone could mix them up during re-assembly.

The fan may be connected to the pcb by a small 2 pin connector, or have the leads soldered directly to the board. Regardless of which way they are connected, I always cut off the leads at the fan.

If you buy a replacement fan that has a connector (the most common type found), cut it off at the connector.

Strip the wires, make a Western Union Splice, solder the splices, and insulate. When I do this on the bench, I use heatshrink tubing, when I do it in the field, I use quality electrician's tape (which doesn't dry out and crack under hot conditions like the 39¢ a roll stuff does). Form the excess wire length into a small loop and secure it with a piece of electrical tape out of the way of re-assembly. secure the fan with screws, orienting the fan for proper airflow direction. (You can determine the airflow direction several ways. Apply 12v for a test, red is pos lead, observe the blade configuration, or as a general rule of thumb, if the fan hub has a sticker on only one side of the hub, air flows away from the stickered side.)

As you put the 3 sided cover back on, squeeze the leg sides slightly so they slide into place with the bottom edges inside the lips of the bottom cover piece. The screw holes should line up perfectly. If they do not, the bottom edges are likely not lined up correctly.

I recommend buying a good quality, ball bearing fan to make sure the repair last a long time.

It is a simple procedure that I have done successfully many times over the years.

 

[Lemon law]

For somewhat of an update--the decider---and the owner of the PC opted to go with a new 430 watt powers supply with a 120 mm fan---and I can't believe how quiet that sucker is. And the klutch--namely me managed to swap power supplies without accidentally pulling out other motherboard wiring. And after swapping the power supplies the puter actually fired up and ran right---which given my usual luck is a minor miracle. So now all is well but I will probably soon install another case fan to get better case cooling.

And I will repair the old power supply fan at my leisure. And that way we will have a extra power supply for diagnostics.