Introduction: Silence a Power Supply Fan

About: Part software developer, part maker.

Hi Everyone,

In my CCTV setup, I use a salvaged computer power supply to provide the 12V needed to power the cameras. The power supply works great but the fan runs at really high speed making the entire setup noisy for my office.

In today’s Instructable, we will look into how we can make it quieter by reducing its speed.


Step 1: WARNING!

This project deals with mains voltage that can hurt you, or even kill you if you are not careful. Only proceed with this modification if you really know what you are doing and at your own risk.

Step 2: Extract and Clean the Fan

What we are about to do is only possible because the power supply is not under a big load and it does not get too high temperatures. The current it provides to the cameras is really low compared to what it actually provides in a computer so its temperature never goes beyond a few degrees above ambient.

To start, I first unplugged the power supply from the AC power and removed the two screws that hold the cover. This can then be lifted up to expose the circuit and the fan.

The fan is held in place with 4 screws to the case and we can undo them in order to remove the fan from the power supply.

Once removed, I used a round paintbrush to carefully clean it up and remove any dust that has gathered on it.

Step 3: Lubricate the Fan

Before starting with any modification, I wanted to see if I can improve the noise levels by lubricating the fan bearing, so I removed the sticker on the back and I removed the rubber cap from the bearing.

I then used WD40 and spray it on the inside. To help it spread, I briefly turned on the power supply and while spinning, I’ve rotated the fan so the lubricant can spread everywhere.

Step 4: Add the Current Limiting Resistor

This helped a little but the fan was still too loud just by the movement of air so I cut the positive wire on the fan and stripped its ends.

I used alligator clips to connect a few different resistors in order to test out how it will work and what speed it will run on and after a few tries, I’ve settled for two 130 Ohm resistors in parallel.

This makes around 65 Ohms in total with a power rating of half a watt and this seemed like a nice balance between fan speed and resistor temperature as they will get quite warm from the current that passes through.

To install them permanently, I’ve used my soldering iron to solder them in line with the positive connection on the fan and I applied a piece of shrink wrap in order to isolate the connection against the rest of the circuit.

Since everything was still running well, I’ve sprayed some more WD40 onto the fan and proceeded to install it back to its place.

Step 5: Add Foam Insulation and Assemble

As an additional step, I’ve cut up some small pieces of packing foam and use them as spacers between the fan and its case in order to act as isolators to prevent vibrations being transferred to the case. I’m not sure if this did any help as the screws still touch the case but after installing the fan, I returned the cover and its screws and I had the modification done.

Step 6: Enjoy!

If in your setup the power supply is in an actual computer or it is required to provides high power output, then I highly recommend against this modification as that might permanently damage your power supply.

This is only viable in situations where you know that there will be no high temperatures or as in my fumes extractor project where I’ve used the same trick to reduce the noise on the extractor fan.

I hope that you liked this Instructable and if you did then hit the like button, subscribe to my YouTube channel and I’ll see you all in the next one.