New PSU powers up only for a few seconds

Powwa / 800w psu
September 21, 2009 at 12:37:38
Specs: Windows Vista
Hi recently bought a new graphics card the ATI 4890 xxx edition and found that my psu didn't have the right connectors for it so decided to upgrade my psu at the same time rather than mess around with molexes and adaptors. I bought a cheap 800w Powwa PSU from ebuyer and when I powered it on it powered up for a few seconds before shutting down. I tried to power up without the new gfx card and got the same issue so sent the psu back as faulty. Now the replacement has arrived and I am having exactly the same issue. It powers for a few seconds and then turns off. Any help would be appreciated as I am stumped.

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September 21, 2009 at 13:48:45
"I am stumped"

Why are you stumped?

Here's your answer >>> "I bought a cheap 800w Powwa PSU from ebuyer"

Notice that the power consumption for an entire system under full load with a Radeon HD 4890 XXX is less than 450W.

Chances are you don't need anything higher than 500W. But it should be a quality name brand unit with a single high amperage +12v rail, not a Powwa. Did you exchange for the exact same PSU?

Here's a Corsair 550W unit with a whopping 41A on the'll handle whatever you throw at it:

Newegg lists the specs:

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September 21, 2009 at 14:17:04
"...recently bought a new graphics card the ATI 4890...."

500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended

Do you connect TWO 75W 6-pin PCI Express power connectors??

The wires for those may not be able to handle 75 watts on an el-cheapo PS.

You MUST remove the AC power source to the power supply when it has been connected to the mboard whenever you connect anything to the mboard or to the PS or make any changes to connections to the mboard or to the PS, and when you plug in or unplug ram or cards in mboard slots! !

If you didn't do that at ALL times, something could have been damaged, including you may have fried the PS or the ram or the video card(s) in (a) slot(s).

I fried one PS when I merely plugged in a hard drive when it had live AC power.

The damaged PS often still partially works - all it takes is for it's controlle chip to be damaged.

Make sure you have the additional power connector from the PS is properly connected to the second power socket on the mboard, other than the main one.

Sometimes the main connector's connection can be finicky.
The wires close to the mboard going into the main power connector/socket should be more or less perpendicular to the mboard surface rather than at an angle.
If in doubt, try unplugging the main connector, plugging it back in again.

You MUST have the 3 or 4 wire cpu fan connector connected to the cpu fan header, and the cpu fan's rpm must be within limits the biosexpects, otherwise most recent mboards will shut off in a very short to prevent the cpu from burning out.

If you are using a 3 wire cpu fan on a 4 pin cpu fan header, it must be connected to the right pins.

The pins on the header are closer to one side than the other, and so are the holes in the female wiring connector from the fan, and the female wiring connector from the fan usually has external ridges that line up with a plastic tab on one side of the header, so the 3 or 4 wire female wiring connector can normally only be installed one way, but it's quite common for the tab on the mboard header to be broken off, and in that case you can install the female connector backwards, or you can install a female connector with 3 wires/holes on the wrong three pins of the 4 pins.

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