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LEDs on CM 120mm fans work at random

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necrokiller

Member
Joined
Apr 20, 2008
Location
Toronto, Canada
I have 4 of these fans in my case:
6971beg_20.jpeg


The LEDs sometimes work and sometimes they don't (1 or 2 out of the 4 Leds on the fan won't turn on). I have a couple of them connected directly to the motherboard and the rest to the PSU. Sometimes the LEDs flicker when my PC is on. I have checked the connections again and again but still its happening.

I just purchased a new Corsair TX750 if that matters. What seems to be the issue? (other Xigmatek fans work flawlessly)
 
The electricity path works like this: 12VDC to the fan, or if from a temp controlling device it could be as low as 7VDC or so to slow the fan. If the voltage drops below xx, the LED doen't have enough voltage to forward bias the silicon junction on the LED thus it won't come on. The fan will be okay, it's way diff than how a semiconductor works, it just spins slower.

If the fans are direct to a 12VDC molex are they fine? But only when they are slowed down through auto mobo temp or a fan controller they don't all light up? Thats the thing to look for.
 
If the fans are direct to a 12VDC molex are they fine? But only when they are slowed down through auto mobo temp or a fan controller they don't all light up? Thats the thing to look for.

Im using this adapter to connect the fans that don't go into the motherboard.
35-233-015-09.jpg

So they are running at their full speed and I can't adjust their speeds. One time all LEDs lit up, then the on the next boot only 2 would work. Same goes for fans connected to the motherboard. (note: this is only with the Coolermaster fans... the xigmatek I have connected have no problems at all)

When I decrease the speed of the fans that are connected to the motherboard, the LEDs go dimmer, none of them switches off until I completely take down the speed to 0%, at which point the fan and all LEDs are switched off completely.
 
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