Scythe S-Flex 120mm SFF21D fan connection adapter

Discussion in 'Cases & Cooling' started by Muse, Apr 2, 2008.

  1. Muse

    Muse Lifer

    Joined:
    Jul 11, 2001
    Messages:
    17,186
    Likes Received:
    3
    Just got 2 of these 120mm fans and I'm wondering what the supplied power connector adapter is designed for. The fan itself has a tri-connection plug that's evidently designed for a MB case fan connection.

    The supplied adapter will connect to the fan's plug and that can go to a 12v molex, and from that supply 12v to another 12v molex supplied device. But there's a 3 pin connector coming off that has only one wire attached and looks designed to plug into a MB case fan connector. Is the idea somehow to support controlling the fan speed from the MB? I don't understand that. If you were going to do that why wouldn't you just plug the fan into that?
     
  2. Old Hippie

    Old Hippie Diamond Member

    Joined:
    Oct 8, 2005
    Messages:
    6,361
    Likes Received:
    0
    Probably just to read the fan speed.
     
  3. Nafets

    Nafets Senior member

    Joined:
    Oct 9, 1999
    Messages:
    440
    Likes Received:
    0
    Since Scythe doesn't wire the fan with both a 3-pin and 4-pin connector, only a 3-pin connector, they include the 3 to 4-pin connector you mentioned. The yellow single wire 3-pin connector that comes off the 4-pin connector is used for RPM monitoring. In some situations a person may want to run the fan @ 12V but the available motherboard fan header may not supply the full 12V for some reason. This happened to me with my S-Flex SFF21E...
     
  4. Muse

    Muse Lifer

    Joined:
    Jul 11, 2001
    Messages:
    17,186
    Likes Received:
    3
    How do you find out if your MB fan header supplies 12v? Measure it with multimeter while the system is on?

    With this fan it's pretty important to get the full 12v because it won't spin up otherwise, is what they say.

    My mobo (Gigabyte K8N Pro) has a header for System Fan and another for Power Fan. Can I connect my two 120mm fans to those?

    Edit: The manual says those fans get 12v, and there's a sensor pin. I don't think the BIOS supports controlling the speed, but will alarm me if the fans fail. It's OK, since I don't believe the fans support reduced voltage, like I say.
     
  5. Nafets

    Nafets Senior member

    Joined:
    Oct 9, 1999
    Messages:
    440
    Likes Received:
    0
    Take your S-Flex SFF21D for example. It's rated at 800RPM @ 12V. So if you plug in into one of your motherboard headers, then it should run at or near 800RPM. If not, then the header isn't supplying enough voltage. The problem I had with my motherboard is that one of my fan headers only supplied around 6-7V, no matter what fan was used. So now it's just used for RPM monitoring.

    The S-Flex SFF21D has a starting voltage of around 9V, so it should start just fine at or even a bit less than 12V.

    A simple test to do is to just plug the SFF21D into each fan header on your motherboard, and check the RPM's in the bios or with Speedfan. If they all report ~800RPM, then you're good to go. Any other fans you plug in should be getting supplied with the full 12V...