View Full Version : how to change mobo voltage on fan prong?

dun dun dun
01-14-03, 04:39 PM
ok, I have this neat idea that I cant really say exactly what. Its a surprise I guess. Anyway, you know the fan prongs on the motherboard? they are 12 volts. well the thing is I need to step it down to 5 volts. How do I do it? I calculated it out that I need a 40ohm resistor, but then I dont know this stuff too well. its been a while........

01-26-03, 01:37 PM
Do you have an multi-meter or an ohm-meter?

Follow the 3-pin socket to the back of the motherboard. You should see 2 copper (or whatever color your manfacturer used) leads tracing out of that area. Check with your ohm meter on both leads to make sure you got the two leads you are looking for.

On either lead, you will have to break the connection, drill two holes, insert the resistor, and solder the connection again.

Check with your ohm meter that you have continuity. That's all. It's simple, but you better be real good with a soldering gun or pen. Remember that the connections made on the motherboard were done with great precision by a machine.

I'm just curious. Why would you want to lower the amount of voltage that goes into your fan header? You will not gain more power to use elsewhere if that's what you're thinking. How much power goes into what is already programmed and set by the engineers. That's where your capictors come to play. The power is not fully dynamic. Any item that has a range of power to play with, that's something that the engineers designed. I would not know how to change that (cause I'm not an engineer for motherboards he he).

If you're just looking to lower your fan speed, just add the resistor to the wire lead on your fan. That's the easiest way.

Good luck.

dun dun dun
01-26-03, 04:52 PM
oh I totally forgot about this post. I also posted at icrontic, and I ended up finding out the answer myself. Thanks for your help. I just was installing "cheap" lighting. Its really small and compact and pretty bright.


the final product....... the resistor is in "pin" 3. But is actually connected to pin 2 and the LED. You can see its bent over. And it just plugs into the fan prong