Question regarding 7V fans.. PSU shuts down?

lemonlimelemonlime Canada Member
edited November 2004 in Hardware
I just got a pair of beasty Delta 120mm big cfm fans. Needless to say, they sound like a bloody jet engine at 12V :eek: . I had my radiator sitting on its side towards my desk when I fired them up, and it literally blew the sheets of my paper off my desk.

I tried wiring one of the delta fans at 7V, (Red to Yellow, and Black to Red) for a potential difference of 7 volts. I am certain I have the wiring right, but for some odd reason, the PSU (antec truepower 430) shuts itself off as soon as I plug the fan in with this wiring configuration?. I tried again with a 300W enermax that I have as well, and it also does the same thing..

I am able to run the fans at 5V without problems (although they dont appear to get enough power, and spin too slowly and make ticking noises too..)..

Has anyone experienced similar problems with 7v mods?.. One note, I am running the PSU outside of my case, as my PC is in pieces for my new WC setup.. Could this have something to do with the motherboard not being connected?

These are certainly power hungry fans, using almost a full amp of current each @ 12volts, I'm not sure if that has something to do with it either.. but the 12V and 5V rails put out a lot of current. 20+ amps on 12V, and 30+ on the 5V rails.

Maybe I should stop being a wimp and just run them at full throttle :hair:

Thanks!

Comments

  • madmatmadmat
    edited November 2004
    With the Antec Tru it has very sensitive short circuit protection, the cause of your problem is that when you try firing up a fan on 7v it sees this as a short and shuts the PSU down to avoid damaging it...(it's a leak across the rails, all the rails on an Antec PSU are regulated seperately) but if you will add a switch in there (there's a thread on wiring a 12v-off-7v switch) to switch from full to off to low speed and start the fan on 12v then switch it to 7v you'll solve the powering off problem or you can simply power the 120's off the fan only rail on the PSU, according to Antec these PSU's can handle them and not break a sweat and you'll be getting your 7v upon startup.
  • lemonlimelemonlime Canada Member
    edited November 2004
    I recently did some modding to my powersupply, and trimmed off quite a few of my unused leads.. unfortunatly, I didn't think, and cut the fan only leads too. :sad2: . I forgot that they put out 7V, as that would have been an ideal solution. I cut them right at the PCB too, no way to reconnect those. Oh well, looks like I may have to explore some of those other options.. Maybe a fanbus or something.. Strange that it did the same thing with the enermax too, must be a similar story with short-circuit protection. Gonna have to figure something out, as these fans are unbearably loud.
  • MediaManMediaMan Powered by loose parts.
    edited November 2004
    7 volt mods will work. You most likely have a short in the wiring as that will cause an immediate shutdown.
  • lemonlimelemonlime Canada Member
    edited November 2004
    Well, I dont think its a short, as I just hooked up a smaller 80mm case fan at 7V, and did not have any problems. It worked just as it should. The Delta fans must draw too much current, and the PSU thinks its a short, and goes into protection. You can see the fans move about a 1/8 of a rotation before the PSU fails.

    I also opened up the psu to see if I could re-solder those fan leads, however when measuring them with my DMM, It read only 5V. It appears that that connection is variable from 5V to 12V, and not 7V to 12V on my powersupply. I believe it is also temperature variable. I also tried to run the fans at ~9V, using the 3.3V rail and the 12V rail, but the same problems occured.

    Well, this leaves me in a crappy situation. I was hoping to keep things simple, and avoid a fanbus, but it looks like I may have to take that route afterall. My only concern is that it may exhibit the same problems, as I'd imagine the fanbuses combine the 5V and 12V rails to acheive lower voltages.

    Anyone have any ideas or suggestions? I would like to keep things as simple as possible..
  • MediaManMediaMan Powered by loose parts.
    edited November 2004
    Go here for reviewage of 5 different fan controllers. My vote would be the Nexus or Sunbeam.
  • lemonlimelemonlime Canada Member
    edited November 2004
    Thanks for the reviews MediaMan.. both of the mentioned models look quite appealing. My primary concern is the high current draw of these fans. If I am to run either of those fan buses, I will be exceeding the maximum amp rating by over 50% :eek: . Each fan draws 1 amp of current.

    I guess these deltas were just not designed for anything but roaring, straight-molex connections. I'm starting to rethink my buying decision, and pick up some more earthly panaflows :( .. Anyone interested in destroying their hearing? I've got some great deltas for sale :D
  • madmatmadmat
    edited November 2004
    Here's a fan controller just up your alley...it handles 20w per channel (1ax12v=12w) and it's 3 channel so you can run a 120 on each of 2 channels and a pair of 80's on the third.
    http://www.mnpctech.com/Mitronfancontroller.html
    The reason I know this about the rails on the Antec was hooking a rather stout 80mm Tornado up in the same fashion you did on my true blue 480w and having the same results, after putting it on a switch to toggle between 12v and 7v and starting it with 12v it ran quite happily on 7v without shutting the PSU down.
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