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December 30, 2011 3:09:56 AM

First off I want to say hello. This is my first post.

I have a homebuilt PC that I made in Aug 09 that has worked perfectly until a month ago. One night it worked fine, the next day it wouldn't do anything, no post, boot, ect. The CPU fan, power on fan and case fan all spin, as well as both HDDs and the DVD. I cannot power off the machine one I turn it on by holding the power button as was normal. I have to turn off the switch on the PSU.

My immediate thought was the PSU, so I had it tested and it came back ok. My next thought was my mobo, so I bought a new one. I just rebuilt the PC and I am having the same problem. I have new memory as well as the new mobo. (I am overly upset I replaced my mobo unnecessarily since I was looking to do that anyway.)

I just did another test on the PSU, which I manually verified I am getting all the correct voltages from each pin. The only thing that I am not sure with is the Pin 20 on the 24 pin connection does not exist. My mobo manual calls for it as a -5V pin, but like I said it is not there, nor has it ever been.

Does anyone have any ideas or can see anything I am missing.

Thank you.

Specs:
AMD Phenom II X4 945 Deneb 3.0GHz Socket AM3
MSI 770-C45 AM3 AMD 770 ATX AMD Motherboard (old)
ASUS M5A97 (new)
OCZ ModXStream Pro 700W
MSI N9600GT-MD1G GeForce 9600 GT
Western Digital Caviar Blue WD3200AAKS 320GB 7200 RPM

Samsung 22X DVDRW SATA

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December 30, 2011 3:30:57 AM

First the -5v is not used by today's PC's. How was the PSU tested? Was it tested under load or just by voltage taken at the pins? I suspect the power supply is bad. Do you get anything on your display?, Can you boot to the Bios? See if you can get your video card checked. If you are sure the MB, Mem., PSU and vid. card are good then you are down to the cpu.
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a b B Homebuilt system
December 30, 2011 3:34:35 AM

The funny thing about PSUs is that they have to have a lot of wires. And that is mainly because all of them are needed. Your PSU, surprisingly seems to be missing the 20th Pin Wire, which itself is pretty shocking. The specifications would have or should listed it as a 19 + 4 PIN Mobo Power, if it were supposed to be like that, wouldn't you say.
I would suggest just picking up another PSU for testing purposes and see if it everything works as it should, with the present config of the rig that you have you shouldn't be needing anything more than a 450W PSU.
And makes sure that the other PSU has all the wires connected to all the pins.

What you seem to have as a PSU is called a SFX PSU. or an ATX12V2.
http://pinouts.ru/Power/atx_v2_pinout.shtml
This surprisingly says something about having to activate PSON by pressing the power button in standby mode.
Meaning the Power Supply ON is activated by pressing the power button while in standby mode, so basically this PSU never goes off, it's always on sleep and the current is minimal, when the PSU is switched on, it's by detection of current flowing to the ground.
I just checked my PSUs 2 old ones one from 2008, one from 2009 and one from 2010. the 2009 and 2010 ones don't have that cable in the pin too, but the old ones have all the cables. But they all work fine.
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December 30, 2011 2:04:58 PM

Dogsnake said:
First the -5v is not used by today's PC's. How was the PSU tested? Was it tested under load or just by voltage taken at the pins? I suspect the power supply is bad. Do you get anything on your display?, Can you boot to the Bios? See if you can get your video card checked. If you are sure the MB, Mem., PSU and vid. card are good then you are down to the cpu.


I had a buddy who works for Microsoft test the PSU, not I am not sure how he tested it. Most likely the same way I did with a multi-meter and not under load. I will take it into a local computer store to see if they can test it under load.

As far as my display goes, I get nothing. I cannot even boot to bios. The only thing that I can tell with my video card is that my display recognizes it as there when it is plugged in and gives me a "no signal detected" message when I take out the dvi connection. I tested another video car that is known to be working and that did not help my issue.

Do you know of any way to test he CPU other than process of elimination. I do not have any other PCs at home I can cannibalize to switch parts either.

Thank you.


alyoshka said:
The funny thing about PSUs is that they have to have a lot of wires. And that is mainly because all of them are needed. Your PSU, surprisingly seems to be missing the 20th Pin Wire, which itself is pretty shocking. The specifications would have or should listed it as a 19 + 4 PIN Mobo Power, if it were supposed to be like that, wouldn't you say.
I would suggest just picking up another PSU for testing purposes and see if it everything works as it should, with the present config of the rig that you have you shouldn't be needing anything more than a 450W PSU.
And makes sure that the other PSU has all the wires connected to all the pins.

What you seem to have as a PSU is called a SFX PSU. or an ATX12V2.
http://pinouts.ru/Power/atx_v2_pinout.shtml
This surprisingly says something about having to activate PSON by pressing the power button in standby mode.
Meaning the Power Supply ON is activated by pressing the power button while in standby mode, so basically this PSU never goes off, it's always on sleep and the current is minimal, when the PSU is switched on, it's by detection of current flowing to the ground.
I just checked my PSUs 2 old ones one from 2008, one from 2009 and one from 2010. the 2009 and 2010 ones don't have that cable in the pin too, but the old ones have all the cables. But they all work fine.


I think I am going to do exactly what you suggest. I will pick up a PSU and test that out while my current PSU is getting tested by someone with the hardware to do it. Thank you.
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December 30, 2011 2:43:45 PM

There are testing devices for a cpu but usually only found in repair shops and labs. The problems you are having are most often caused by the power supply (my first thought), MB (already replaced), memory (also new), video card and lastly cpu.
Fingers crossed that when you get the new psu all will be well.

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January 1, 2012 2:06:17 AM

Update. I had my PSU tested under load. It appears to be fine. I think I am down to the CPU. Is there any chance that on my first build, I added too much thermal compound and created an thermal insulator and cooked the CPU?

Thanks for the help.
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a c 122 B Homebuilt system
January 1, 2012 2:56:12 AM

Probably not. Modern CPU's just shut down to protect themselves.

While CPU's do fail, it's actually pretty rare.

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 (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 (this is also a good way to test the power switch and the associated wiring), then back to 5 volts when you release the case power switch. 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.

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a b B Homebuilt system
January 1, 2012 3:02:12 AM

Have you checked the PINS of the CPU to see if any are broken or bent? Also check for discoloration of the pins.
If there is a possibility, check the CPU in another rig.
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