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What the heck happened to my PSU?

Forum CPU & Components : Power Supplies, PC Cases & Case Mods - What the heck happened to my PSU?

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justdohnut   10-22-2009 at 08:32:14 AM

Hey, I had a bit of a mishap today and wanted to know what in the world happened.

So I had just installed a new 150gb velociraptor, and a new fan because I was worried about temperatures. I booted up fine, and my computer was working just great for about 4 hours. Then I was reading up on stuff on airflow, and realized my fans were not blowing in the optimal directions, so I decided to re-route them. Upon installing these fans, I plugged back in the power cable, flipped the power switch, and nothing happened. The motherboard usually lights up, as well as the small LED light in the PSU. Tried to turn it on, nothing, so I figured something must be wrong with the power supply. I had a spare computer laying around, tested the PSU on there, and it too would not power on. Putting back the original PSU, the spare computer booted up just fine.

Then, just to make sure the motherboard was ok, I tested it with my spare computer's power supply. The motherboard's power LED light went on, and the CPU fan was running and everything. So I believe the motherboard seems to be running fine.

Do you think perhaps the PSU was a dud? I've had this rig for about a month and a half now, and have had no problems. I overclocked the computer about a week and a half ago, and it was running fine. The velociraptor was installed today and it seemed to be running fine as well. After the velociraptor I had rebooted at least twice. Was 650w enough power? Maybe I didn't calculate correctly..?


My specs are as follows:

Antec True Power 650w

Antec 300 case

ASUS P6T SE LGA 1366 Intel X58 ATX Intel Motherboard

Intel Core i7 920 OC @ 4.0gHz, 1.42v

Scythe Mugen 2

Velociraptor 150gb

2x WD Digital Caviar Black 500gb in Raid 0

1x Seagate 7200rpm 160gb SATA

CORSAIR XMS3 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666)

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Bronze CPUs badge jsc   10-22-2009 at 08:47:01 AM

Unplug all of the fans except the CPU fan. Unplug the Velociraptor to reduce the thermal load in your computer. Go back to default BIOS settings.

Now try to boot. If the system works, one of the newer components is shorted.

A 650 watt Antec has plenty of power for your system.

I am also concerned by your statement that airflow wasn't optimal.

On all the Antec "gamer" cases (300, 900 & 902, and 1200), the front fans pull in air and the back and top fans exhaust air. That is optimal.

Check out this thread:
http://www.tomshardware.com/forum/ [...] t-problems

Pay close attention to the breadboarding.

Reply to jsc
justdohnut   10-22-2009 at 10:11:45 AM

Thanks for the speedy reply--

I checked out the checklist and I seemed to have followed every step. I reset the CMOS, then tried the breadboard technique, where just CPU , heatsink, and CPU fan were plugged in. I plugged in the PSU, power cables to the motherboard, and nothing happened. When plugged in, and turning the power switch on the PSU, it makes no noise and I don't see the red light I'm used to seeing. It's dead?


In regards to the airflow situation, I had the fans correctly installed as you stated, only I had the side fan in exhaust rather than intake. I wanted to make that simple change and ended up with a disaster! Thanks for your help, and I would appreciate any other suggestions before I pack up the PSU and send it for a replacement.

Reply to justdohnut
Bronze CPUs badge jsc   10-22-2009 at 10:35:20 AM

The little read LED on the motherboard is powered by the standby power supply, a small 5 volt, always on power supply. If the LED is off, your PSU is probably dead.

Reply to jsc
justdohnut   10-22-2009 at 10:44:37 AM

Alrighty, just as I feared. Thanks again for the help and leading me to the guide - definitely a big help for me to read and refer to in the future.

Reply to justdohnut
Bronze CPUs badge jsc   10-22-2009 at 05:38:54 PM

And if you have access to a voltmeter:

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.

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 dead.

Reply to jsc
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