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Computer wont turn on, Receiving power i think

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April 22, 2011 6:42:47 PM

Ok so about a year ago i built a computer for the first time. I didnt run in to many problems and got it running. Well i moved houses and i decided to vaccum and clean the inside off all the dog hair and dust. So i did a dry cleaning, only using windex on the inside of the fan. Now i plug it in and the mobo green light comes on. When i hit the power button all the fans spin a half inch and stop. I tryed doing a search for this but i couldnt find anything.

1 x ASUS M4A79XTD EVO AM3 AMD 790X ATX AMD Motherboard
1 x XFX HD-587X-ZNFC Radeon HD 5870 1GB 256-bit DDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card with Eyefinity
1 x CORSAIR CMPSU-750TX 750W ATX12V v2.2 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply
1 x AMD Phenom II X4 965 Black Edition Deneb 3.4GHz Socket AM3 125W Quad-Core Processor HDZ965FBGMBOX
1 x G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Dual Channel Kit Desktop Memory Model F3-12800CL9D-4GBNQ
1 x Seagate Barracuda 7200.12 ST3500418AS 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
April 22, 2011 7:29:14 PM

i tryed both the RAM singly and that didnt solve the problem so im at a loss. I made sure all the plugs were secure incase i loosened one during the cleaning.

Ok i now tryed different outlets. nothing

i then removed everything except the motherboard, PSU and CPU. and nothing.
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a c 122 B Homebuilt system
April 22, 2011 7:50:12 PM

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.

You may want to jump straight to here. After all, the PC worked before you started cleaning. Only instead of pulling the motherboard, try disconnecting all the cables and start over, testing at every step.

If not, continue.
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

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: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%. If you have a white wire (many modern PSU's do not), it should be -5 volts.

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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April 22, 2011 7:59:23 PM

ok thank you. Thats the info i need. i dont mind working but i need good info and thats hard to find. Yea i think ill just rebuild it testing at each step.
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April 22, 2011 9:13:48 PM

Ok so i have the CPU, PSU and mobo hooked up after i took out everything. It now turns on. Whats next in the order? I was gonna do RAM(1 at a time), then hard drive, then cd drive then GPU.
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