Really dumb PSU question (Is mine DOA??)

Putting together my first build. PSU was the first thing to show up. It has a fan (adjustable via a switch to low-auto-high) and an LED, so I plug it in without anything else attached to see if it will work. Nada. Fan doesn't run at any switch setting. LED does not come on. About 5 seconds after it is unplugged, I hear a very faint whine come from it (like something is discharging).

Voltage on the back is properly set to 115V for USA.

Am I correct in assuming that a PSU doesn't need to be under load to have these features come on?

Jape :(
12 answers Last reply
More about really dumb question mine
  1. Awesome! I have a fan arriving tomorrow. I'll unpack the PSU and try that trick (shorting the green and black wires on the mobo connector).

    By the way, I found your posts very helpful in putting together this build. Thank you.

  2. okay just kidding
  3. The on/off switch was the only part I was really comfortable with. :wink:

    Yes, I tried that, along with each of the three fan switch positions. Plus plugging the whole unit into different outlets.

    I'll test mpilchfamily's suggestion tomorrow and report back.

  4. Actually yes it is true. the switch in the back does not turn the psu on... how do you turn on your computer? does the switch on the psu turn your computer on? the switch at the front of the computer shorts the pwr sw pins on the motherboard and then the motherboard in turn shorts the green and a black wire on the 24 pin connector to turn the psu on. you don't technically need load on the psu when you short it but you should if you don't want to fry it.

    If you don't know what you're talking about keep your mouth shut.
  5. if i were you id just leave it until you have the rest of your components and start the build. you dont want to chance frying your PSU before you even start.
  6. Follow-up:

    Received a couple of other components (fan, card reader, etc) but decided not to test it. Although I found the green wire on the 24-pin connector, I also found 9 or 10 black wires. I didn't want to guess. 8O

    I did notice that the 120mm fan I purchased has two receptacles along it's power cord. The terminal connector is very tiny, which I assume is a standard fan connector that clips right onto the mobo. There is also a large, pass-thru 4-pin connector in the middle of the cord that I assume is the "molex" type that is so common. I'm hoping this means that the fan can either be plugged into the mobo or can use the molex to feed off a line going to another component (since my mobo has been criticized for having too few fan connectors).

    Unless both need to be plugged in and the direct mobo connection is involved with data (fan control/monitoring) rather than power.


  7. Thanks!

    If you have software that adjusts the speed of the fan, does the fan need to be plugged into the mobo? I recall reading that a fan plugged directly into the PSU will simply run full-tilt the whole time (which isn't necessarily a bad thing, eh). :)

  8. Hey, this is actually starting to make sense. :)

    FYI, I tried your suggestion, and it worked great. I hooked an LED fan up, shorted the green to a black, and everything started up beautifully. I didn't run it for more than a second or two, but the fan was whisper-quiet and seemed to push a lot of air. I can't wait for the rest of my stuff.

    Thanks again. I'm sure I'll have lots more questions in about a week.

  9. either / or not both....

    Also, I prefer using a fan controller but it's really up to you. Fan controllers will typically use the big 4 pin molex.
  10. Quote:
    either / or not both....

    Also, I prefer using a fan controller but it's really up to you. Fan controllers will typically use the big 4 pin molex.

    This sounds like it contradicts mpilchfamily's response. Unless you are referring to some separate unit that controls the fan's speed (as opposed to a mobo that would control it via software if the fan was plugged directly into the mobo using the alternate, smaller connector).

    If I'm on the right track, how would you control the fan controller? Would it have a switch, or would it somehow be controlled via software as well?

  11. Understood. Sounds like something I might like. The mobo I'm most likely to get (Gigabyte 956P-S3) has numerous complaints about its poor fan control. I'd like a unit that monitors the case temp and will reliably handle the fan control. I'm surprised I didn't stumble across one of these units already. I'll start looking.

  12. Nexus specializes in fan controllers. I have 8 fans in my case (including the 4 on my rad) and I actually use 2 different fan controllers, one for the fans on my rad and my side fan (all intakes) and one for my 3 exhaust fans.
Ask a new question

Read More

Power Supplies Fan LED Monitor Components