Problem with new computer build. Could use some help.


Jul 14, 2009
I just recently got done with building my new PC. The first problem I had was that the PSU came DOA and I RMA it. I got the new one and plugged everything in but when I try to turn it on the led lights on the fans flash and the fans start to turn but then it stops after a second. So I knew something is shorting it out and the PSU just kicks off then I have to turn off the PSU and wait for the motherboard led to go off and try it again. There are no lose writes running under the board and I tried to disconnect and test if it was one of the other components but it wasn't. Then I decided to unplug the CPU power connector and it powered on. The fans, video card, SSD, and DVD drive all ran but its not going to work because the CPU isn't getting power. I'm not sure what is wrong. I think its either the motherboard or CPU but I'm not sure. I read that the bad PSU could have damage the board. Can anyone help me?


Aug 5, 2011

That's what I would suggest. When you do that, if your mobo has integrated graphics then take everything off of the board except the cpu and one stick of RAM. If it doesn't have integrated graphics then try the same thing but with your video card. If it still won't boot, try each stick of RAM individually. If you still can't get it to post, then odds are some of your hardware is bad.
danraies has the right idea.

First, complete system specs?

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.

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. 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.

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.



Jul 14, 2009
The specs are:

AMD Phenom II X6 1090T Black Edition Thuban 3.2GHz Socket AM3 125W Six-Core Desktop Processor

ASUS M4A87TD/USB3 AM3 AMD 870 SATA 6Gb/s USB 3.0 AMD Motherboard

Kingston HyperX 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600

OCZ Fatal1ty 550W Modular Gaming Power Supply

Video Card
ZOTAC ZT-50401-10L GeForce GTX 550 Ti

Optical Drive
Sony Optiarc CD/DVD Burner Black SATA

Plextor PX-M2 Series PX-128M2S 2.5" 128GB SATA III Internal Solid State Drive

COOLER MASTER Storm Scout SGC-2000-KKN1-GP Black Steel / Plastic ATX Mid Tower Computer Case

I haven't been able to build it outside the case yet but I'm doing it today. I'll try what danraies said.


Jul 14, 2009
I found out the problem. It is actually really stupid. The four pin CPU power connector isn't keyed so it was in the wrong way. I thought all connectors were designed to not allow that. Thanks for the responses everyone.