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4 yr old system: no signal/no post

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February 16, 2011 8:18:03 PM

Hi all; I tried troubleshooting my problem based on what information I gathered online. I respect the knowledge and experience of the community here so I decided to post my findings and hear any suggestions the experts may have.

I disconnected everything and just set the motherboard on a phone book. Only the CPU, HSF, PSU and system speaker are connected to the motherboard.

I have the following components: mobo: GA-965P-DS3 / CPU: Core 2 Duo E6600 / PSU: OCZ GameXStream 600W

Every component was newly installed when I built my computer (used tomshardware at that time too!) and the system ran stable until now. One day I turned on my system and all the fans started spinning, but like the title says there was no signal reaching my monitor and the computer refused to post. There are no beeps, but after I "breadboarded" my system I was able to notice a faint clicking sound coming out of the system speaker (it sounds exactly like this: http://www.youtube.com/watch?v=UrLLSVudP8s Note: this is NOT a video of my system, its just some other poor fellow that has a system with a problem). When the problem started the PSU would power off and on every couple of seconds, but now it just stays on until I flip the PSU switch off.

I followed in detail all the suggestions made in the following sticky: http://www.tomshardware.com/forum/261145-31-perform-ste... and while I was testing my PSU while it was plugged into my "breadboarded" system I discovered that the gray wire was only providing between 0.14V & 0.15V after powering on the system. Here are some other values I got: Orange wires were 3.1V, Yellow wires were 12.6V, the Purple wire was 5.2V, the Red wires were 4.6V and the Blue wire was -12.4V.

Since the voltage on the gray wire does not register anywhere near 5V, is it safe to assume my PSU was the culprit all along? Is it likely my CPU + Mobo are damaged? I intend on buying a new power supply and see if my system will post with it; any other suggestions are appreciated.

More about : system signal post

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a c 122 B Homebuilt system
February 17, 2011 7:42:42 PM
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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.

OK. You did that.

If not, continue.

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.
February 17, 2011 9:09:50 PM

Best answer selected by Kanoobie.
February 17, 2011 11:06:27 PM

Thanks for the post jsc; wish I had seen it before I went out to get another PSU. I would like to post an update since I picked up another PSU to test with. After inputting what parts I use into the antec PSU wattage calculator, it calculated that I just need ~400 watt PSU under conditions of frequent use and heavy load. I ended up getting a 430W Thermaltake PSU from my local store.

Anyways, I plugged the new PSU into the my breadboarded PC and lo & behold Beeps :pt1cable:  ! I was elated, and I started adding all my internal components one by one until I was able to enter my BIOS and load Windows. After checking that my temp and Voltages were stable I rebuilt my PC using my case. When I hit the power button this time... I get no signal and no post again :fou:  ! I started removing components (in my case) and noticed without my video card connected I would get an error beep. If only I had read jsc's post before getting another PSU I thought.

I stripped my case of all its components again and decided to breadboard again. Miraculously my computer posted once more! If I hadn't read on tom's I would think there was some dark voodoo at play here, but I am pretty sure something in my case is shorting my board and I am likely running a PSU that may be too weak.

Any suggestions on how to pinpoint any shorts? I know there are no loose screws and the standoffs are in place. In case you want to check if my PSU can handle the load, off the top of my head, here is a list of what I use:
mobo: GA-965P-DS3
CPU: Core 2 Duo E6600
PSU: replaced what I had with: Thermaltake TR2 W0070RUC 430W
Ram: 2 gigs (1x1) of DDR2
Video: ATI Radeon x1950xt
HD: SATA Seagate Barracuda
DVD-RW/CD-RW: 1 drive
# of devices plugged into my USB: 3
Antec P180 Case Fans: 3 x 120mm fans

Thanks!
!