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Weird Problem/Condition with new build.

rickon66

Golden Member
Oct 11, 1999
1,809
3
81
Been putting together a new computer this past week and was in the process of putting in the finishing touches when I came across a strange situation. I have all of the major components in place and everything is working as it should. I want to organize the cables, etc. so I cut off the power and shut off the power switch on the power supply. To my suprise one of the led fans keeps glowing and another fan is still spinning slowly. I thought that was odd so I pulled the AC plug out of the power supply and the fans still keep glowing and spinning. I am confounded because no power is even hooked up to the PC and the fans keep going. The only cable connected is the DVD-I cable and sure enough, when I disconnect it the fans stop. Has anyone else experienced this apparent voltage feedback through the video cable?
 

Rhoxed

Golden Member
Jun 23, 2007
1,051
3
81
does you monitor support power out of USB ports? (meaning it has USB ports you can charge a cell phone on or something?) That's the only think i could think of off the top of my head, that would be sending power back to the PC.
 

rickon66

Golden Member
Oct 11, 1999
1,809
3
81
The monitor is a Dell U3011, but I would not think USB would affect the video cable. My concerns are if the voltage will harm monitor, video card or power supply. It is coming through the 12v cable on power supply. Very weird
 

SolMiester

Diamond Member
Dec 19, 2004
5,331
17
76
I think he's saying if you have USB on the monitor and the monitor has its own power, a 5v current maybe traveling back from the monitor to the USB port on the motherboard and then powering the led fan......

I have no experience in this, but could be a possibility?
 

rickon66

Golden Member
Oct 11, 1999
1,809
3
81
I tried swapping in another video cable and a different fan and the problem still persists. The different fan feeds directly from the motherboard via 3 pin socket whereas the first fan was powered off of the power supply from one of the 12V cables. I looked at the pinout of the DVI cable and pin 14 has 5 volts on it. It looks like I am getting voltage passing though the video card back into the motherboard and ito the 12v suppply system. Some additional comments. It gets even stranger as I next unplugged the power to the Dell monitor and the fan continoues to glow and run at slow speed. To make a long story shorter, the cause of the problem was my I7-930 computer that was connected to the Dell on another DVI cable. I disconnected the other computer and hooked it up to a 26" Samsung HHD260 and problem went away. So I never found the root problem, but I did get rid of the glowing fan/voltage leakage that I was concerned with on the new computer(3370K with GtX670), didn't want to fry that one yet.
 
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