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Computer Won't Do Anything

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April 27, 2011 4:53:27 AM

Hey guys,

I'm having a little problem. Today I replaced my stock i5-2500k fan with a Thermaltake Silent 1156. Since replaced, I haven't been able to get the computer to power on once. When plugged in the green LED on the motherboard (P8P67 LE) lights up, but when I hit the power button nothing happens. Literally, nothing. No fans. No HDD spinning. I've triple-checked the jumpers for the power button, reset the CMOS, reseated the HSF multiple times. The computer was working fine before I installed the HSF, so it seems hard to believe it's the PSU. I'm taking it to Micro Center to have it looked at tomorrow, but in the meantime I'm too bothered to sleep, so I figured I'd ask for input.

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April 27, 2011 5:10:50 AM

Make sure that thermal paste is not squeezed outside of heatsink area. If it is conductive (some silver based are), it may short if it touches side of CPU or mobo.
April 27, 2011 5:40:06 AM

I'm pretty sure the thermal paste isn't silver-based, but I checked anyway and it looks clean. I can only conclude that it's either a motherboard short or I managed to break something installing the new HSF. Hopefully the latter seems unlikely, but I'm not sure how easy it is to break or destroy something without knowing you've done it.
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April 27, 2011 6:39:27 AM

To make sure motherboard does not short with case, you can take it out of the case and run it outside. Make sure you put it on something that does not conduct electricity at all. Antistatic bag from your motherboard would be perfect if you still have it.
a b B Homebuilt system
April 27, 2011 7:48:13 PM

jalexbrown said:
I'm pretty sure the thermal paste isn't silver-based, but I checked anyway and it looks clean. I can only conclude that it's either a motherboard short or I managed to break something installing the new HSF. Hopefully the latter seems unlikely, but I'm not sure how easy it is to break or destroy something without knowing you've done it.


In answer to your question, it is fairly easy to break or short something without knowing. Voltages smaller than 0.5V passing from your finger to a component (that is too small to be felt or detected by you) are easily enough to fry it. How likely is it? Well, I gave up on using a wrist strap years ago because I simply got in the habit of grabbing the chassis periodically while working on computers and grounding myself.

If you are certain you've followed all the procedures correctly, I would do an overall system check. Its possible while moving the PC or whatnot you've accidentally disconnected a cable or something. Open the case and make sure all your cables are firmly connected, make sure all add-in cards and ram modules are firmly seated. Double check all power supply connections to the mainboard and components. (Like the 12v P4 connector located near the heatsink)

If all this looks good then I would tear down the machine as suggested above and see if mobo alone outside the case will power up. Try adding components one at a time to isolate a bad one.
a c 122 B Homebuilt system
April 27, 2011 9:52:32 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.

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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