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X-Finity PSU 660W -is it toast?

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July 16, 2009 4:58:09 AM

My PSU - Ultra ULT 31849 600w X-Finity Power Supply

For some reason my motherboard isnt posting and one helpful guy in here suggested my PSU may have crashed

yet when i turn on power fans, etc seem to operate but still doesnt post to monitor screen

Question #1 - this PSU has 2 dual 80mm fans - does anyone know are they supposed to both work at same time or does one kick in when there is a drain on the PSU? I ask because the fan on the inside isnt turning while the fan on the inside of the case does not

Question #2 - So does that man a PSU can appear to be working and yet not put out enough juice for motherboard etc

More about : finity psu 660w toast

a c 144 ) Power supply
a c 156 V Motherboard
July 16, 2009 8:22:29 AM

Q2. Yes. You could have a problem with the 3.3 volt output, 5 volt output, or the "PowerOK" signal to the motherboard and the fans would still work.

Try to verify (as well as you can) that the PSU works. If you have a multimeter, you can do a rough checkout of a PSU using the "paper clip trick". You plug the bare PSU into the wall. Insert a paper clip into the green wire pin and one of the black wire pins beside it. That's how the case power switch works. It applies a ground to the green wire. Turn on the PSU and the fan should spin up. If it doesn't, the PSU is dead. If you have a multimeter, you can check all the outputs. Yellow wires should be 12 volts, red 5 volts, orange 3.3 volts, blue wire -12 volts, purple wire is the 5 volt standby.

You can also carefully measure the wires through the back of the power plug (carefully, carefully).

The gray wire is really important. It sends a control signal called something like "PowerOK" from the PSU to the motherboard. It should go from 0 volts to about 5 volts within a half second of pressing the case power switch. If you do not have this signal, your computer will not boot. The tolerances should be +/- 5%. If not, the PSU is bad.

Unfortunately (yes, there's a "gotcha"), passing all the above does not mean that the PSU is good. It's not being tested under any kind of load. But if the fan doesn't turn on, the PSU is probably dead.

If it is dead replace it with a better quality unit.
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a b V Motherboard
July 16, 2009 2:32:19 PM

Question #1: Both fans should work when the PSU reaches a certain temperature.
If not, the fan should be replaced by the factory. Do not attempt to do this yourself, unless you have read a lot and are aware of the risks.
July 16, 2009 5:03:25 PM

forgot to mention this is not a new build - built almost 3 years ago - it was working fine the morning i logged off to go to work - that evening i turned it on and it didnt post at all - i turned it on and went to do something else for about 10 min - came back to sit down and cruise the net and a black monitor was lookin back at me

evongugg - the fan outside the case runs all the time - while the one on the inside turns slowly because of the airflo created by the outside fan

another note: the one inside thats not on turns but not smoothly

thanks JSC


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