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Old 06-29-2005, 04:12 PM   #1
skilectron
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Question Maximum fan power from mobo contacts

Is it OK to use a 92mm Vantec Tornado which draws a little over AMDs 0.7A stock fan at 1A? It already has the RPM sense and I could easily get the wire leads and pin contacts into the blank ones so it runs from the CPU mobo fan connector instead of molex- an easy 5 min mod

DFI NF4U-D I know specs no ratings at all for fan headers in their manual, but its bios fanspeed controls are already there for a couple of the headers and far better than all but the most overpriced fanspeed controllers- and I want all my other fans fullspeed 24/7 anyway.

I dont actually have a Tornado and wont bother unless this is for certain not enough to overload the boards CPU fan header.
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Old 06-29-2005, 04:35 PM   #2
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extremely bad idea would never use a tornado running off the cpu header will fry it pretty much straight away...ampage is ok but the 12 watt draw from the tornado will deffo short the header out
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Old 06-29-2005, 04:38 PM   #3
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Quote:
Originally Posted by Kevster2004
extremely bad idea would never use a tornado running off the cpu header will fry it pretty much straight away...ampage is ok but the 12 watt draw from the tornado will deffo short the header out
The DFI fan headers are rated at a max of 6.24W (0.52A).
http://www.dfi-street.com/forum/show...8&postcount=12
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Old 06-30-2005, 02:21 AM   #4
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Unhappy

I never actually tried using the stock retail Venice fan the CPU shipped with, but its unusually high current rating sure stood out. This is the only reason I mightve even suspected a Vantec Tornado could somehow be borderline safe since this fan had no molex converters, warnings about its power requirement or anything.
On the 70x15 fan:
AVC
MODEL DE07015B12U
DC12v - 0.70A S016
BALL BEARING

0.7A x 12v= 8.4w loaded by 1 fan header. Make me wonder if theyre trying to get those that dont OC to burn stuff up more often
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Old 06-30-2005, 04:06 AM   #5
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well connecting ya tornado would deffo end up burning the header out...connecting any high performance fan to any motherboard header is dangerious thats why we have fan controllers
personally i'd never risk overloading the headers its really bad idea
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Old 07-02-2005, 12:06 AM   #6
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I know at this point a Tornado is too much

I agree that high perf fans on mobo fan headers is risy.
But that still doesn't say anything for the unexplained VERY HIGH 0.7A load supposedly sucked by AMD's stock fan.

Im still assuming this is true since noone seems to know otherwise. I guess it really doesnt matter for me bc I use a molex powered high-perf fan anyway, but Im still curious bout it.

Ill bring this up to AMD telling them my mobos much lower 0.52A max ratings and see what they say bout it. this otta be good
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Old 07-02-2005, 03:01 PM   #7
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Cool Mystery Solved

I measured the AMD stock fan on a couple test supplies with a DMM and determined the 0.70 A rating is clearly a typo and believe it meant to say 0.07A!

I also measured a 0.25A rated CoolerMaster 60x10mm as a control.
On a 5v,1A regulated wal-wart (voltage measured stiff@5.03v), the undervoltage almost wasnt enough to spin up the AMD fan. Measured 0.03A. The CoolerMaster 0.05A.

On the 13.8v,0.9A unregulated wal-wart: Open load voltage=19VDC. I added an 8ohm series resistance to buffer what the fan sees down a little. Ive used it before to test 12VDC fans and only ever hurt a fan once bc it was accidently connected it in reverse
The coolermaster caused a 0.23~0.24A reading on the DMM. About as expected. Actual voltage was a hair over 15v. It was 1 loud fast little fan with that not that Id risk subjecting it to that for more than a few secs
The Venice stock fan however only caused somewhere around 0.08~0.09A to my surprise (it probly wouldve been right on 0.07A had the supply not been >12v). Actual voltage was nearly 17v indicating the how small the true load really was.

I know had the load really been 0.7~1A range with that walwart, the load+series resistance wouldve caused the load to effectively see around 13v.
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Old 07-02-2005, 03:44 PM   #8
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Quote:
I measured the AMD stock fan on a couple test supplies with a DMM and determined the 0.70 A rating is clearly a typo and believe it meant to say 0.07A!
Had to be!
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