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Dead Power Supply?

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Last response: in Components
April 26, 2010 2:16:06 AM

I built a new rig a couple of months ago and it's been great. The build went without a hitch and there have been no problems at all. The PS has been running a little hot and I've been looking for a good sale to replace it.

AMD Athlon II X4 635 Propus 2.9GHz
4GB OCZ Obsidian DDR3 1600 RAM
HIS Radeon HD 4770
Ultra V Series 400W PS

Tonight, I unplugged the PC and moved it to a different part of the house. I hooked everything back up and it's dead. Won't POST. PS fan doesn't spin. Nothing. Nada.

I tested the outlet with a radio and a lamp and it's fine. I took the PS cord from a working PC and it made no difference. I opened the case and there is no burn smell or evidence of overheated components anywhere in the case or on the board. When I plug in the power cable, the power LED on the board lights, but the PS fan doesn't spin. I checked all power connections and the case front connections and everything is as it should be.

My first inclination is that the PS is dead. It's wierd to me that the board power LED lights but the PS fan doesn't spin.

What am I missing?

Thanks in advance for the help.


More about : dead power supply

a b ) Power supply
April 26, 2010 5:08:45 AM

There is always a standby 5 volt charge going to the motherboard no matter its on or off so that is what you are seeing the problem sounds like it is a PSU problem though. When you press the power button on your computer the motherboard sends a signal to the PSU to turn on and that is why you see lights on the board that is the 5 volt lead that rarely goes on PSU's since it really doesnt power all that much these days everything is powered off the 12 volt for the most part which is always the first to go on a PSU sice it is the most used section of the power supply.

Your unit is very low quality only providing 20 Amps to the 12 volt rail which equals to 240 watts. So you have a 95 watt processor, 4770 which draws upto 84 watts then a had drive drawing another 10 watts or so and maybe some fans and an optical drive so you are right up there areound 200 maybe a little more. For those cheap PSU that is the peak amount it could put not what it can put out continuos.

So I would suggest getting a good quality unit like Antec, Corsair or SeaSonic those 400 watt units will actully be able to put out that wattage continuously.

So what I am trying to say is get a new quality unit and you will not have this problem again cheap PSU will end up costing you more in the end then it would have cost if you got a quality unit.
a c 144 ) Power supply
April 26, 2010 4:21:39 PM

The bare minimum PSU I would use in a system like yours is a Corsair 400CX (30 amp 12 volt rail):

You have worked through our standard checklist and troubleshooting thread:

I mean work through, not just read over it.

Breadboard - that will isolate any kind of case problem.
Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.
You do have a case speaker installed, right? If not, you really, really need one. If you case or motherboard didn't come with a system speaker you can buy one here:

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU.

The best bet is to test a PSU to replace the it with a known good one of similar power capacity. Brand new, out of the box, untested does not count as a known good PSU.

Next best thing is to get (or borrow) a digital multimeter and check the PSU. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs
this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

This checks the PSU under no load conditions, so it is not completely reliable. But if
it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU. You can carefully probe the pins from the back of the main power connector.
Related resources
May 2, 2010 12:26:34 PM

I found the link to the paper clip test for the PS and confirmed that the PS was dead. Before I saw the above recommendation, I purchased a COOLER MASTER Elite 460 RS-460-PSAR-J3 460W PS. It passed the paperclip test out of the box. I connected it and the PC still would not run.

I disconnected everything from the board except for the processor and PS, and still could not make the machine start. In frustration, I threw the case front power switch across the room and had a beer. Just for giggles, I tried to start the machine with a screwdriver shorting the power pins and it started right up. I've never had a switch fail so I did not consider it a component and had left it connected to the board. I dropped in a power switch from another case and the machine runs fine.

The machine is reassembled and my son is playing Halo on it right now. I'm embarrassed that I missed something so simple.

Thank you for the help.

a c 248 ) Power supply
May 2, 2010 1:26:42 PM

Stuff happens.