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Faulty Power Unit?

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6 replies

by abcd1234jk

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Recently built a computer for myself (core i7, vista 64 os, geforce card, asus mobo) which ran fine for a week, left avg to scan while i took a shower cam back and computer was dead

upon trying to restart it the cpu fan (cooler) turns on for .5 seconds before it turns off, as if it does not have enough power to start.
both the leds on the motherboard ( the reset and power ) light up, it does not get to bios so no beeps. the system power led also lights up for half a second.

all connections were checked 3x over and are good

any help is appreciated

6 replies

by thechas

Well, did you buy a cheap or a good power supply?

If you paid less than $20 (US) for the power supply, I would agree that you should start with the power supply.

Another thought, is what is the wattage rating of your power supply?
Anything less than 500 Watts is too small for this system.

Next would be the RAM or CPU.

Chas

by rob miners

Remove the Power cord from the PSU to discharge the Capacitors in the Power Supply. Then press the Power button for 10 seconds to discharge the Capacitors on the Motherboard.
Plug the power cord back in and see if it will start. If it does replace the Power Supply Unit (PSU).

Swap the Power switch to the front panel with the Reset switch to rule out a faulty switch.

Reseat the Central Processing Unit: Use an Anti-Static Wrist Strap to ground yourself or by placing the back of your hand on the Power Supply Unit and not moving your feet. This will prevent electrostatic charge from building up and by not taking this precaution it is possible that you could inadvertantly cause damage to the PC from an electrostatic discharge. Then remove the Heatsink, giving it a thorough clean and reseat the CPU applying new CPU grease. If the Fans spin freely when you give them a spin they are probably OK. If there is resistance replace them.

Clean the golden edge of each memory stick with a soft rubber/eraser, remembering not to touch the golden edge of the memory stick. Check with one stick at a time, remembering to disconnect the power from the PC.

by abcd1234jk

I checked each ram one at a time still the same thing happened. Also reseated the cpu and cpu fan with new thermal paste.

Once i unplugged the 2 4pin connectors from the motherboard (coming from the power supply) and tried that the system booted but the video card was now dead as no output to the monitors and the video card fan was not on (turns on when getting power)video card is powered by a pair of six pin connectors from the power supply.

The power unit was not cheap i believe around $75 and is 730w.

by oh smeg

So go here to the Corsair Site and use their PS Calculator to see what size PS you should be looking at.

http://www.corsair.com/psufinder/default.aspx

There are two types of PS's one is a Peek Value so it can supply the rated current in Watts for short periods of time and the other is a constant Feed PS that can supply 100% of the rating 100% of the time.

Naturally it is better to have a Constant Feed PS as these produce better results and protect the insides of the case much better than the other type.

The down side is that they are the expensive ones but you can use a 350 W one of those where as a 700 W of the other type would not be sufficient for that particular system.

I always recommend Antec PS's because they are the best I have ever used and provide superior protection and voltage to the insides of the case than any other PS I have ever used.

Col

by mjd420nova

If the unit works without the video card extra power connectors, then the power supply is under powered or over speced. The unit turning on and then turning off right away does indicate that too much power is being drawn and it is shutting down to protect itself. I'd check the P/S rating to be sure its an average rating and not a peak rating. I always over power my units, by at least a third more than would be the peak rating.

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