jasybee2000
26-08-2007, 08:03 PM
I bet you are all eager to find out why firey is in the title so i'll explain my recent MIS-Adventures in PC modding which is Lowering Case fan RPMs to take less voltage to make a PC quieter.
Okay, basically after seeing a load of sites on the net explaining how case fans usually run off the 12V line and can be made to run using less power enabling a quieter fan, I thought yeah okay lets have a go at that seeing as I have a noisey 120mm fan in the front of my case cooling my hard drives.
After reading up on several websites all saying the same thing. I noted the layout of the voltages and were the 12V, 7V and 5V lines were. I had a cable that was left over from a Chimera Akasa fan which by the looks of it allowed the fan to take power from the molex while enabling you to plug the sensor wire into the 3pin header on the mainboard so that the bios could still note the speed although it would be fixed of course. Now heres where the fun begins. I tested the idea by plugging in an 80mm led fan into the 3 pin connector on the lead and then changed the pins in the molex to draw power from the 5V line instead of 12V. I then put the sensor cable part into the mobo. When I powered it up I went into the bios and checked the speed of the fan! Sure enough it was running at 1041rpm instead of 2650rpm and I couldnt hear it at all. Okay so that worked it seemed. I then powered off the system and moved the pins in the molex to use the 7V line.
Now this appeared wierd in the sense you had to connect one to the 12V+ and the other to the 5V+ lines. I checked diagrams from different sites and ensured the polarity was correct. Then when I powered on the system it appeared to work as normal at least for about 1-2seconds. That then followed by a massive cloud of black smoke and I could see the fan sensor cable which is yellow was actually glowing bright orange! I immediately rushed to the mains and powered it off. Upon inspection the casing on the sensor lead had burned away. Upon testing the system it all worked fine and no damage resulted I am puzzled as to why it did this as i'm 100% sure the polarity was correct as I followed the steps of 3 different sites that said the same thing. I was hoping to quieten down a back chasis fan on an expensive system which connects to the mainboard header under POWER FAN and its speed is read by the BIOS. For some bizarre reason it spins at the max rpm of 2550 and is noisey. I wanted to lower its RPM as the BIOS reads the speed of this fan but doesnt adjust it which is strange?
Anyways I have tested the 5V 120mm fan for a few hours now and so far so good it is working without flames or smoke but the fan sensor is not plugged in as there are no spare 3 pin headers on my mainboard as they are all used up by other fans.
I find this completely puzzling in the sense that it worked fine with 12V, and 5V, but when I tried 7V the sensor lead glowed? WTF? Could it of been a dodgy lead?
I have 1 more of these leads spare which ive taken a picture of, and ive labeled the wires as per a modding website. Tell me if this is correct or not. I presume that it should be safe to connect it to the molex power and the 3 pin header simultaneously as there doesnt appear to be any power draw from the 3 pin connector. It only has 2 wires on the outside for sensor and grnd? so why the **** did it go up in flames?
I wanted to try this on a the chasis fan on my expensive new system and also read the sensor by using the 3 pin connector on the mainboard while drawing 5V from the psu molex but I am a bit tenacious about doing so?
Can someone give me their opinion?
Heres the link to the cable I modded (this one is currently in its default state. i.e set to use 12V)
http://server50222.uk2net.com/~jaseybee ... exlead.jpg (http://server50222.uk2net.com/~jaseybee/fanmolexlead.jpg)
Your help and wisdom is appreciated!
Cheers,
JB
Okay, basically after seeing a load of sites on the net explaining how case fans usually run off the 12V line and can be made to run using less power enabling a quieter fan, I thought yeah okay lets have a go at that seeing as I have a noisey 120mm fan in the front of my case cooling my hard drives.
After reading up on several websites all saying the same thing. I noted the layout of the voltages and were the 12V, 7V and 5V lines were. I had a cable that was left over from a Chimera Akasa fan which by the looks of it allowed the fan to take power from the molex while enabling you to plug the sensor wire into the 3pin header on the mainboard so that the bios could still note the speed although it would be fixed of course. Now heres where the fun begins. I tested the idea by plugging in an 80mm led fan into the 3 pin connector on the lead and then changed the pins in the molex to draw power from the 5V line instead of 12V. I then put the sensor cable part into the mobo. When I powered it up I went into the bios and checked the speed of the fan! Sure enough it was running at 1041rpm instead of 2650rpm and I couldnt hear it at all. Okay so that worked it seemed. I then powered off the system and moved the pins in the molex to use the 7V line.
Now this appeared wierd in the sense you had to connect one to the 12V+ and the other to the 5V+ lines. I checked diagrams from different sites and ensured the polarity was correct. Then when I powered on the system it appeared to work as normal at least for about 1-2seconds. That then followed by a massive cloud of black smoke and I could see the fan sensor cable which is yellow was actually glowing bright orange! I immediately rushed to the mains and powered it off. Upon inspection the casing on the sensor lead had burned away. Upon testing the system it all worked fine and no damage resulted I am puzzled as to why it did this as i'm 100% sure the polarity was correct as I followed the steps of 3 different sites that said the same thing. I was hoping to quieten down a back chasis fan on an expensive system which connects to the mainboard header under POWER FAN and its speed is read by the BIOS. For some bizarre reason it spins at the max rpm of 2550 and is noisey. I wanted to lower its RPM as the BIOS reads the speed of this fan but doesnt adjust it which is strange?
Anyways I have tested the 5V 120mm fan for a few hours now and so far so good it is working without flames or smoke but the fan sensor is not plugged in as there are no spare 3 pin headers on my mainboard as they are all used up by other fans.
I find this completely puzzling in the sense that it worked fine with 12V, and 5V, but when I tried 7V the sensor lead glowed? WTF? Could it of been a dodgy lead?
I have 1 more of these leads spare which ive taken a picture of, and ive labeled the wires as per a modding website. Tell me if this is correct or not. I presume that it should be safe to connect it to the molex power and the 3 pin header simultaneously as there doesnt appear to be any power draw from the 3 pin connector. It only has 2 wires on the outside for sensor and grnd? so why the **** did it go up in flames?
I wanted to try this on a the chasis fan on my expensive new system and also read the sensor by using the 3 pin connector on the mainboard while drawing 5V from the psu molex but I am a bit tenacious about doing so?
Can someone give me their opinion?
Heres the link to the cable I modded (this one is currently in its default state. i.e set to use 12V)
http://server50222.uk2net.com/~jaseybee ... exlead.jpg (http://server50222.uk2net.com/~jaseybee/fanmolexlead.jpg)
Your help and wisdom is appreciated!
Cheers,
JB