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Troubleshooting - PC not posting

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May 28, 2011 12:11:02 AM

I've just moved all my PC components into a new case, and it won't post any more.

When I press the power button, all the fans and power led comes on, but I don't hear any beeps and the screen stays blank.

Not sure if the MB hasn't survived the transfer - is there anything I can check?
May 28, 2011 12:39:10 AM

Just noticed something odd. I've transferred all the components back to the old case, and there is a hissing / squeaking noise coming from the old power supply. The noise only happens when the PSU is plugged into the mains and the PC is off. As soon as I power it up, the noise stops. But the PC still doesn't boot.
a b ) Power supply
May 28, 2011 2:48:35 AM

check to make sure that the ram is seated correctly. onboard or aftermarket gpu??? do you have another power supply?
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a b ) Power supply
May 28, 2011 3:20:50 AM

All your parts?
a c 144 ) Power supply
May 29, 2011 2:05:27 AM

OK. It worked in the old case. Then you moved the parts to a new case and it doesn't work. So you moved the parts back to the old case and the parts still don't work. Right?

My first thought is that you forgot to connect something.

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%.

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.
May 29, 2011 1:42:40 PM

First wanted to say, fantastic troubleshooting guide. I've built a few PCs so I have checked most of the stuff anyway, but there were a couple of things to check (standoffs and CPU power).

The standoffs were factory installed (it's a Silverstone Grandia GD06, which only takes mATX boards, so it appears they've just supplied it with them fitted for that board type) but I've double checked they're all in the right places.

Regarding the CPU power connector, my motherboard only has a 4-pin socket, and the new PSU has an 8-pin plug that can be split in half. Seemingly, either half can be plugged in to the MB socket (both have their own catch). Does it matter which is used (the PSU manual neglects to mention).

I've tried a barebones configuration (just the CPU plugged into the board, along with the 2 power connectors, speaker, and power switch). Still the same result with no beeps on POST.

The case came without a speaker, so I've grabbed one from my server, but I'm not sure now whether it works. When I restarted the server, I heard what I'd always thought was the POST beep even though I was holding the speaker! It looks like the server case has it's own speaker connected up to the temperature sensors, and it only beeps once on startup, so I guess the speaker I took out is probably broken.
May 29, 2011 2:22:57 PM

Grabbed a working case speaker, and still no POST beeps at all.

One more thing is, the guide suggests a lot of computers won't POST without the CPU fan plugged in. I've checked this on my server, and it is certainly true on there, and there doesn't seem to be any way to disable the feature in the BIOS.

I've been having a quick look about at the components I could use to rebuild it. It's a dedicated HTPC, and the current Core 2 E6400 is still easily fast enough for everything it does, so I'm considering something like the new Core i3-2100T. It's still over double the speed of what I have now, and I was thinking 35W is low enough for passive cooling, and therefore proper silence. But that would mean no CPU fan.

Is there any way to tell whether a motherboard can POST without a CPU fan? I'm looking specifically at the Asrock H67M-GE/HT, as it is one of very few boards with an internal USB3 header, and the GD06 has USB3 front ports. The manual mentions configuration of CPU fan speed, but not whether the detection can be disabled.
a c 144 ) Power supply
May 30, 2011 10:46:18 PM

For the CPU power connector, use either half if they fit.

asc99c said:

One more thing is, the guide suggests a lot of computers won't POST without the CPU fan plugged in. I've checked this on my server, and it is certainly true on there, and there doesn't seem to be any way to disable the feature in the BIOS.

Check the PC health section of your BIOS. It can be disabled there. You may need to connect a heatsink fan so you can boot the first time.

Enter the BIOS, turn off the feature, save the BIOS, turn off the feature, then unplug the fan.
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