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Hush Those Fans
Easy (& Free!) 5V & 7V Fan Mods

Every moving part in a PC generates noise. The motors in optical drives and hard drives and the cooling fans that keep your hardware cool are the most notorious culprits in your case. All of these moving parts can result in an annoyingly loud PC. But don’t fear; there are many things you can do to quiet a system down without spending a mountain of cash.

Most of today’s power supplies, graphics cards, and CPU coolers have fans that will throttle their speed (and thus, noise produced) based on temperatures or load, so even the highest-end products aren’t too disruptive—we’ll ignore those for now. You can install your hard drives in vibration-dampening enclosures that minimize their noise levels. And you can silence your case fans in a number of ways, too. As for optical drives, well, don’t leave a disc in the drive when it’s not in use, and it’ll be quiet. This month, we’re going to focus on case fans because they tend to be one of the noisiest parts in a typical PC; yet, they’re one of the easiest to mod. We have a method in store that will quiet them down, and, perhaps best of all, you won’t have to spend a penny to execute it.

How Does It Work?
The majority of fans included with cases or sold individually are designed to operate at 12V. The PSU feeds 12 volts to the fan’s motor, which causes the fan’s blades to rotate and circulate air. Increasing or decreasing that 12V feed, however, makes the fan’s motor spin at different speeds. Increase the voltage, and the fan will spin faster, move more air, and generate more noise. Conversely, lowering the voltage will do the opposite. That’s the basic premise behind this mod.

There are limits to how high or low to set a fan’s supplied voltage. Feed too much voltage into the fan and its motor will burn out; don’t supply enough voltage and the fan won’t spin up at all. Generally speaking, feeding 13 to 15 volts to a fan is a safe bet and won’t cause any damage. Conversely, 4 to 6 volts is usually enough to get the fan spinning. Because our ultimate goal with this mod is to quiet noisy case fans, we’re going to focus on ways to lower the input voltage without purchasing any additional parts.

The Standard Disclaimers
Before we begin, we want to stress a few points. First of all, if your PC runs hot and you’ve had issues with overheating, don’t perform these mods. You might want a quieter machine, but slowing down the fans will circulate less air through the case, making a hot system run hotter.

Also, the 7V mod below puts extra stress on your power supply. To supply 7V to a case fan, its positive and negative leads must connect across the +12V and +5V feeds coming from the PSU, which put extra strain on some of its voltage regulators.

But if you have a high-quality power supply and aren’t running more than two or three fans in a 7V configuration, you shouldn’t have any trouble.

There’s also a chance that a power supply’s short circuit protection mechanism won’t like a component connected across two positive leads, but since when is a mod risk-free? We can say, however, that over the years, we’ve performed this mod numerous times without incident. We also want to emphasize that some fans don’t operate reliably when you configure your PSU to supply a substandard voltage. Should you try the 5V or 7V mods outlined here, keep your case open for a while to ensure that your fans are spinning up properly. If the fans don’t consistently spin up, it’s best to revert back to a standard 12V configuration to prevent overheating.

12V Configuration
12V is the standard configuration for most case fans. Assuming the fan has standard colored wiring, the red lead connected to the fan’s motor is positive, and the black is negative. In this configuration, the fan’s positive lead mates with a peripheral connector’s yellow, +12V wire, and the negative lead connects to either of the peripheral connector’s black, common ground wires. With a 12V feed supplied, the fan will spin at its maximum rated speed and airflow.

5V Configuration
The 5V (and 7V) configuration requires a modification to the fan’s wiring. To perform this mod, we recommend using a PSU pin removal tool to speed the process and minimize your frustration. Pin removal tools are available at numerous online retailers for just a few dollars. Though in a pinch, it’s not absolutely necessary to use a pin removal tool.

If you look at the pins in a female peripheral connector (the type of connector usually attached at a case fan), you’ll see four flared barbs at bases of the pins that lock them in place. When the barbs are flared out, it’s impossible to pull them back through the connector without damaging the pins or wiring. A pin removal tool depresses these barbs so the pins are no longer locked in place. If you don’t have a pin removal tool, you can use a small flathead screwdriver to bend the barbs inward, letting you push the pin back through the connector. Just remember to flare the barbs back out before reinserting the pins so they’ll stay in place. We’ve also used the plastic tubing from inside some ballpoint pens as a pin removal tool.

To perform the 5V mod, pair the fan’s positive lead (red) with the power supply’s +5V lead, which also happens to be red. Using the pin removal tool, we removed the pin connected to the fan’s positive lead, moved it to the other end of the connector, and reinserted it.

7V Configuration
The 7V mod is a little trickier and may seem a bit counterintuitive to the electrically inclined. To perform the 7V mod, you have to move the fan’s negative lead to a new position in the connector. Using the pin removal tool, we dislodged the fan’s negative lead (black) and reinserted it to the far side of the connector, opposite to the positive lead (red). With the fan’s wires in this position, the fan’s positive lead mates with the PSU’s yellow +12V wire, and the fan’s negative lead mates with the PSU’s red +5V wire. This may sound strange to some of you because it seems like we’re shorting two positive rails and the fan’s negative lead isn’t connected to a common ground. But, in practice, this configuration results in a net of 7V running through the fan’s motor (12V – 5V = 7V). This, as we’ve already mentioned, slows the fan down to reduce its noise level.

Other Possibilities
The more adventurous of you out there may be wondering what type of additional magic you can work using PSU’s other rails; there are, after all, more than just the +12V and +5V rails available in an ATX power supply. And in fact, there are a number of other effective voltages that become available by bridging wires in the power supply’s 20-/24-pin main ATX power connector. 8.7V, 17V, and even 24V configurations are possible using combinations of the power supply’s rails.

However, we wouldn’t recommend experimenting with these wiring configurations. Typically, a power supply’s -12V and 3.3V rails can’t handle significant loads, so we don’t advise connecting peripherals to them that they’re not designed to support. It’s also far more difficult to modify and make new connections in a 24-pin ATX power connector safely. Ultimately, the risks are greater than the rewards, so we recommend sticking with either the 5V or 7V mods.



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