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System won't turn on

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  • Homebuilt
  • Systems
Last response: in Systems
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April 15, 2011 5:13:44 AM

Hi,

I just assembled a new system today, and for some reason the system will not turn on.

Here is my set up:
CPU: Intel Core i5-2500K Sandy Bridge 3.3GHz (3.7GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor

Mobo: ASUS SABERTOOTH P67 (REV 3.0) LGA 1155 Intel P67 SATA 6Gb/s USB 3.0 ATX Intel Motherboard

Memory: G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL8D-8GBXM

PSU: CORSAIR HX Series CMPSU-750HX 750W ATX12V 2.3

Graphics Card: MSI N560GTX-TI Twin Frozr II/OC GeForce GTX 560 Ti


When the 24-pin connector and 8-pin connector are plugged in, it turns on for a split second then powers off - the fans jerk - but nothing else happens after.

When the 8-pin connector is unplugged, so that only the 24-pin connector is plugged in, the system powers on for about 2 seconds and power off.

When I test the power supply with the paperclip trick, the two case fans connected to it spin indefinitely.

I tried breadboarding, but it still won't work.

I am thinking it is an issue with the psu - maybe it is defective and is not supplying enough power. What do you guys think?

More about : system turn

April 15, 2011 3:06:32 PM

Basics....do you have the cpu power connector plugged in?

While something could be defective, the more likey issue is something is not connected properly or you are missing a connector. Recheck EVERYTHING in that system...
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Best solution

a b B Homebuilt system
April 15, 2011 7:54:44 PM

The troubleshooting checklist in my signature was created to diagnose this exact problem if you perform EVERY step in the checklist.
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a c 122 B Homebuilt system
April 15, 2011 8:01:32 PM

sleeny,
When you said you breadboarded your system, did you do something like the following:
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.


Hey, shortstuff. Haven't seen you in awhile. How have you been?
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April 16, 2011 1:05:15 AM

Thank you for your replies.

I confirmed the psu is fine by hooking it up to another computer. Upon closer inspection, I found one of the socket contacts on the motherboard is bent. I do not have a magnifying glass, so I cannot see it well, but even without a magnifying glass, one pin stands out. Can this cause the no boot issue?
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April 26, 2011 2:39:02 AM

Best answer selected by sleeny.
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