5v mod on fans

The other day i was messin around w/ an old fan and an old at ps, I was thinking about the 7v mod and realized that if you turn the4 pin connector around you get 5v. The fan ( a top fan rated at one db lower than the delta (comes w/ gladiator) was virtually quiet; I really couldn't hear the fan unless i put my ear right next to it. Now you will have to modify the 4 pin connector so it will fit upside down (backwards) so that it is more square like. (this is really eaisy)

Thought this might help someone since its free and extreamly easy, well not exactly free, you lose performance (but save your ears )

There's one problem tho, a lot of fans need higher voltage to start spinning.

KILLorBE (Jul 15, 2001 06:41 p.m.):
There's one problem tho, a lot of fans need higher voltage to start spinning.

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Eh? I've started and run my 80mm and 120mm fans on voltages as low a 3V using a AC/DC adapter.

I have tried 5 and 7 on my 7k delta and it works fine. Right now I have a variable resistor on my delta so I can really control the speed. My temps hardly rise when it spins slower and I can bare the noise.

... This is the word from PC Power and Cooling when asked by me about running fans at 7 volts:

The noise problem is not the fan but cavitation due to intake air restrictions or, exhaust air restrictions from the case fan grill. Also, A fan will not start consistently at 7 volts since most are not guaranteed to start at much below 9 volts DC. Lastly, you would trip the overvoltage regulation of the +5 Volt line, in our supplies, if you were to do the wiring configuration you describe. The only universal way to regulate the voltage to a fan is to use a rheostat inline with one lead of the fan to induce a variable voltage drop to the fan.

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You might keep this in mind if you choose to try it. The rheostat method really is better, I'll grant them that. Still I've used this method with PC Power and Cooling's power supply without the result described above. You will want to make sure your fans do start reliably and you'll want to make sure the power supply doesn't trip. They make great power supplies and I appreciate their thoughts in this matter.

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**NOTE** The 'me' and 'I' is NOT me but someone else.

One more thing if you want to have adjustable fan speed. I recommend a rheostat instead of a variable resister since variable resisters cant always take the current. My variable resistor gets warm so I am a little uneasy using it.

I hate to trifle, but a Rheostat is a variable resistor, just like a Potentiometer. They typically have different methods of implementation and the Rheostat is most often in the form of wound resistive wire with a wiper, whereas a Potentiometer often uses a carbon trace with a wiper. The Potentiometer usually has less current carrying capability (hence lower wattage) than the Rheostat. Both usually come with three terminals. I have seen Rheostats so big, they had a Steering Wheel on them for turning them.

Hoot