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System won't power up

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  • Homebuilt
  • Power Up
  • Power Supplies
  • Systems
Last response: in Systems
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January 13, 2012 12:29:42 AM

Got a call about a system that wouldn't power up (family). Took power supply from my working system at home and brought it with me.

When I arrived to work on system I found that the green light for network was working but nothing else would power up. I removed the power supply and replaced it with the one I brought from my home system. Keep in mind that I built both of these system in 2007. They have been flawless until this issue. When I installed the PSU and powered the system still the same thing, nothing would power up. Thinking nothing of it other than there was a short somewhere and it needed to be tested at a shop. I returned home and installed the PSU back into my (what was a working system) case, powered up and nothing but the LED board lights came on (ASUS CROSSHAIR)

I then took the system to a local shop, they tested the PSU and told me that the 12v side of the PSU wasn't working. I ordered a new Corsair 1050w, it arrived today and I installed it only to find that the LED board lights came on and nothing else powered up. Not sure what to do at this point, frustrated. Anyone have any suggestions other than a new system build?

More about : system power

January 13, 2012 12:42:10 AM

Unfornately, If you blew your PSU and then blew your mob from overload; there isn't much you can do. Although I doubt it will work it worth a try, pull the cmos battery, this will set the bios back to default and give it try. If unsuccessful take it to your shop and have them test just to confirm. Also you may want to keep in mind 2007 puts it at 5 years and most people are going to be replacing every 3-5 years, you got your money worth out of it.
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January 21, 2012 12:50:44 PM

Quote:
Unfornately, If you blew your PSU and then blew your mob from overload; there isn't much you can do. Although I doubt it will work it worth a try, pull the cmos battery, this will set the bios back to default and give it try. If unsuccessful take it to your shop and have them test just to confirm. Also you may want to keep in mind 2007 puts it at 5 years and most people are going to be replacing every 3-5 years, you got your money worth out of it.


All of the above has already been done but the local shop wasn't able to test the board. I needed to assure myself hearing it from someone else that the mobo was gone. Thanks for the reply. Already got a new system to replace it. Was a pricy mistake for sure. Thanks again and have a great weekend.
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a c 122 B Homebuilt system
a c 144 ) Power supply
January 22, 2012 4:02:10 AM

Work systematically through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If no luck, continue.

[/#0cff00]
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.
http://www.tomshardware.com/forum/261145-31-read-postin...

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

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. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire (standby power supply): 5 volts always on. The green wire should also have 5 volts on it. It should go to 0 volts when you press the case power button (this is also a good way to test the power switch and the associated wiring), then back to 5 volts when you release the case power switch. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

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.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

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.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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