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Thread: Case fan modified. Safe?

  1. #1
    Constant Bitrate cafn8's Avatar
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    Case fan modified. Safe?

    Hey guys. I'm wondering if somebody can help me out.

    At work I have a 450mhz G4 Mac. It was purchased through ebay, but had a bad case fan so my boss replaced it. As long as I've had it, the fan has been very noisy and was getting on my nerves. I compared it to the guy's fan next door to me and noticed that mine put out much more air but was much, much louder than his. His is a computer is a 433mhz G4, so I didn't think that really accounted for the difference in cooling capacity. Our conclusion was that the replacement fan was just much more powerful (and noisy) than was required.

    Here's my question: will putting a 5w 50ohm resistor in line with the fan harm anything? It's much quieter and still seems to be putting out as much, or more breeze than the guy's fan next door. I should maybe note that the fan is driven by wires directly from the power supply. Could this harm the fan or the power supply? I REALLY don't want to screw up my computer that I earn my living with, but the decreased roar from the computer really makes my office more comfortable to work in. Thoughts?

  2. #2
    FLA gospeed.racer's Avatar
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    IMHO a fan that spins too fast may not allow the air to cool the equipment as it pulls or pushes past it. Just my opinion though.
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  3. #3
    Variable Bitrate Cherub211's Avatar
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    No, the resistor wouldn't hurt anything and it will slow your fan down, while you are at it you might as well wire up a pot and tune the fan to your liking.

  4. #4
    Constant Bitrate cafn8's Avatar
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    Quote Originally Posted by gospeed.racer
    IMHO a fan that spins too fast may not allow the air to cool the equipment as it pulls or pushes past it. Just my opinion though.
    I'm more concerned about the effects of adding a 50 ohm resistor on the electrical components.

    By the very scientific "hand in front of the fan" test my fan seems to be blowing about 11.8% harder than my co-worker's which seems adequate to cool the computer.

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    Maximum Bitrate deadweasel's Avatar
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    Unhappy

    Quote Originally Posted by cafn8
    I'm more concerned about the effects of adding a 50 ohm resistor on the electrical components.

    By the very scientific "hand in front of the fan" test my fan seems to be blowing about 11.8% harder than my co-worker's which seems adequate to cool the computer.
    That's a pretty accurate hand you have! My fans all blow somewhere around 50% more air than they need to. Heh.

    Plopping a resistor on that bad boy shouldn't hurt it. It's a simple DC motor after all. It shouldn't affect anything else in the case.

    Also, the only time you should have to worry about too much airflow preventing proper cooling would be if you were to build a wind tunnel out of your case. Current case and fan designs won't allow you to have too much airflow though. The trick is to keep the case's ambient air cool so that the processor, video card and hard drives have enough cool air to pull from to cool themselves.

    Instead of hard wiring a resistor, may I suggest a prefab fan controller? You can get them for in-case, front bay or pci slot mount. It's not as haxor-ish of a solution, but it will certainly alleviate any fears you may have of cut-and-paste electronics solutions...
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  6. #6
    Variable Bitrate Ashlawn Kemling's Avatar
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    Another trick you can do is to make a connector that has the positive wire hooked up to the +12v and the negative wire hooked up to the +5v. 12 - 5 = 7volts. Trust me, this works and it perfectly normal to do in a computer. (JUST DO NOT use the connector for anything else!)

    You can never have too much cooling. My CPU fan pushes 120cfm of air where as a normal CPU fan pushes 35cfm to 40cfm.

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    that sounds like an awfully bad thing to do, thats effectivly a 7v short across power supply :S
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  8. #8
    Constant Bitrate cafn8's Avatar
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    Hmm. Interesting idea. Just an update: I'm still using the 50 ohm resistor in the fan and haven't really noticed any more problems than before (I am running Mac OS 9.2 after all, so I can't expect too much stability ) I leave the computer running 24-7 and nothing unusual has happened. The fan is now much quieter and I can once again hear my streaming audio and overhear others' conversations from other offices. (That's our version of inter-departmental communication)

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