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Computer PSU silencing

Author: Zoltan Puskas
Categories: electronics

My roommate’s server was a bit louder than what he wanted so he asked me to if I could help reducing the noise a bit. By far the loudest component being the constant speed PSU fan I decided also make the RPM adjustable so we can fine tune it to an optimum speed resulting in proper CFM and reduce noise levels.

PSU fan control

The box is built from old low end parts and since it’s running headless it is also missing the power hungry GPU. Because of this the whole setup requires little power and the PSU is working well below it’s nominal power rating. This means less heat dissipated so a lower CFM will suffice without damaging the unit. Also most units have overheating protection built in, meaning it will at worst case, shut down the machine.

I solved the problem by adding a 5W 100Ω linear potentiometer onto the power line of the fan. To fix the potentiometer I have cut one bar out of the PSU’s venting grill and screwed in place. It was placed on the inside as adjustments are not required beyond the set up phase. The wires were soldered on and hot glue was used for better mechanical support as well as insulation.

The box has been operating silently and reliably for a month now without any issues. This solution was much cheaper and faster than buying a brand new passive PSU or one of those high end units with built in fan control.

Modifying the PSU

Taking apart the PSU Cutting space for the potentiometer in the grid Soldered and insulated potentiometer in the fan power circuit Installing the potentiometer Assembled modified PSU Installed PSU in home server