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FIRST PC BUILD ! - power switch issue/fan issue

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  • Power Supplies
  • Cases
  • Power Switch
  • Power
  • Components
Last response: in Components
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February 3, 2010 8:16:41 PM

Building my first PC

Motherboard: 750i SLI NForce
CPU: Intel Core 2 Quad Processor
Power: ULTRA 850 Watt ATX Power Supply
Case: Cooler Master Centurion
RAM is installed in the slots

Nothing else installed yet, I am at "power check" phase in the buld.

Questions:

1). My Case fan (at rear of case below the rear power switch) has two power connector, both four prong, one female, the other male. Which goes to where? I have one (the female connector) plugged into a connector on the power supply, it fits fine.

2. Upon power checks, I pushed the "POWER" switch on the front of the case, and the following happened:

Case fan, Power Supply Fan, CPU Fan, all spun up then died after approx 30 seconds. If I push "Power" switch again, this occurs again. They never "stay on"

Note: With the power supply switch on (the main switch at the rear of the case), a red LED is observed illuminated on the motherboard. (If this helps with the diagnosis)

More about : build power switch issue fan issue

a b ) Power supply
February 3, 2010 8:28:53 PM

Switch on back of psu is master power off switch, kills mains power.

Fans normally connect to the headers found on the motherboard, sounds like you may have connected it to the psu fan control cable that controls how fast psu fan spins.
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a b ) Power supply
February 4, 2010 1:05:50 PM

Normally one would plug a case fan into a mobo SYS_FANx male pinout and use the mobo's fan speed control system to run it, with speed controlled by the case internal temperature as measured by a sensor on the mobo. If you connect it instead to a set of leads from the PSU you get no fan speed control unless you also insert your own module in the line.

Now, I do find your story confusing. I have never heard of a PSU that has a MALE 4-pin power output connector (you did say it was the fan's FEMALE connector you plugged in). Nor have I heard of a case fan with two sets of leads and connectors. So, for starters, read exactly what the case manual says about how to use the connectors on the fan.

Some PSU's have a FEMALE connector like a fan connector (usually just 3-pin) on leads coming out, and they are intended to plug into the mobo's PWR_FAN male pinout. In fact this merely feeds the PSU's internal fan's speed signal to the mobo for monitoring; it does not actually provide power or speed control to that fan. But I'm still left wondering what 4-pin MALE connector you used coming from the PSU. Even if that gender was wrong and you used a FEMALE 4-pin output from PSU to a MALE connector on the fan wires, the only 4-pin female output I can recall is those used for power to a 3½" floppy drive, usually on the same set of wires as the larger 4-pin female Molex connectors.

The power-on behavior you describe MAY be a symptom of poor CPU cooling. If the CPU cooler is not correctly fastened down over the CPU in good thermal contact (or if the thermal paste was not done correctly), heat removal will be too slow. As a result the system will start up but in less than a minute (sometimes more like 10 to 20 seconds) the CPU temperature will rise beyond the limits and the mobo will shut down the system to protect the CPU from overheating. Check the mounting of your CPU cooler. Review how you applied the thermal paste. Or, if you have a cooler that came with thermal paste already applied, did it have a protective plastic film over it that you forgot to remove?
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a c 243 ) Power supply
February 4, 2010 1:33:07 PM

billpritjr said:


1). My Case fan (at rear of case below the rear power switch) has two power connector, both four prong, one female, the other male. Which goes to where? I have one (the female connector) plugged into a connector on the power supply, it fits fine.

It sounds like a molex pass-thru power connector, it allows you to power your fan and add more components to the line, no problem there.
Our standard trouble shooting guide
http://www.tomshardware.com/forum/261145-31-read-postin...
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February 4, 2010 4:42:05 PM

I just learned via a computer tech friend that my motherboard may detect that no Hard Drive nor Video Card, etc is hooked up yet and may shut itself down upon realizing this. He recommended I continue with the build.

The CPU cooler came with pre-affixed thermal paste, no plastic cover. NOTE the CPU fan, the case fan, and the power supply fan all spool up and all die at exactly the same time.
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a c 144 ) Power supply
February 5, 2010 8:46:22 AM

billpritjr said:
I just learned via a computer tech friend that my motherboard may detect that no Hard Drive nor Video Card, etc is hooked up yet and may shut itself down upon realizing this. He recommended I continue with the build.

Unlikely. The 750i BIOS is based on the 680i BIOS. You do not need a hard drive, mouse or keyboard to successfully (one short beep) complete the POST. Without a video card, the POST completes - unsuccessfully (one long beep and 2 or 3 short beeps).

Silence, then a shutdown means that the POST is not finishing.
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