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Why does my computer not POST?

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June 14, 2010 9:48:00 PM

Yesterday I was working on overclocking my CPU/Graphics. i was succesful at first, but then as I turned settings up, the settings didn't apply. So I tried resetting my bios by taking out the CMOS Battery. After that the settings still didn't apply, but I don't care about that anymore. So I set all the settings back to default, but when I tried to boot, the windows 7 screen started to come up, but "froze" when it shows the logo, but it looked to me like the logo was still pulsing.

So I tried safe mode, that show'd me that the last thing on the screen to load was Disk.sys. Then I reset the CMOS again and still no luck. I tried taking out sticks of RAM, but the computer isn't even posting now. All the fans rev up, and lights come on, but NOTHING shows up on the screen. I tried taking out the card and re-installing it, that didn't work.

So now I have no screnn (post, or boot) So first, how do I get the screen to show? Second, how do I get windows to boot, thanks. One idea, maybe its the CMOS Battery is running out? The computer is a hand-me-down, so I would guess its a several years old.

Last night I reset the BIOS overnight while having all the RAM, Graphics, and Drives unplugged, that didn't work.

Today I took the whole thing apart, set out the motherboard onto a anti-static bag and plugged in only power, graphics, and CPU fan. Still no beep codes, or post screen

Specs:
ASUS P5n-E SLI Motherboard
Core2 Quad Q6700
4GB DDR2 800 RAM
XFX 8800 GTS
Corsair 525W PSU
Antec 900 Case
DVD Drive
Several Hard Drives

More about : computer post

June 14, 2010 9:59:53 PM

Taking out the battery won't reset the BIOS. I could, but likely not.

Check to see if there are BIOS Reset jumpers on the motherboard. You may have to go online to get a diagram of the mobo to find out. If its a package (i.e. Dell, HP, Compaq, etc.), go there. If it's a home built, go to the mobo manuafacter (i.e. Asus, Abit, EVGA, Gigabyte, etc.).

Also, resetting the BIOS may have raised a couple of other issues, like hard drive settings (i.e. IDE instead of ACHI). If you can check the "default"setting of the BIOS, compare them to what you actually have. Motherboard manuals usually hae recommend settings which are wrong for the hardware in them.

Oops, looks like you have an Asus mobo. Let me check something...

Hope this is a link to your mobo, so you can download a manual, if needed: http://usa.asus.com/product.aspx?P_ID=KyHOsOKWujC2QguJ
June 14, 2010 10:27:53 PM

foscooter said:
Taking out the battery won't reset the BIOS. I could, but likely not.

Check to see if there are BIOS Reset jumpers on the motherboard. You may have to go online to get a diagram of the mobo to find out. If its a package (i.e. Dell, HP, Compaq, etc.), go there. If it's a home built, go to the mobo manuafacter (i.e. Asus, Abit, EVGA, Gigabyte, etc.).

Also, resetting the BIOS may have raised a couple of other issues, like hard drive settings (i.e. IDE instead of ACHI). If you can check the "default"setting of the BIOS, compare them to what you actually have. Motherboard manuals usually hae recommend settings which are wrong for the hardware in them.

Oops, looks like you have an Asus mobo. Let me check something...

Hope this is a link to your mobo, so you can download a manual, if needed: http://usa.asus.com/product.aspx?P_ID=KyHOsOKWujC2QguJ


Great idea, but I did that before, it didn't so I tried it again and still no luck. I've tried each RAM Stick in every slot too.
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June 15, 2010 1:17:10 PM

based on what is written, I would say you may have shorted the motherboard. If you can test each of the other components (Ram, video, CPU, PSU) in another machine to verify they work (each individually) but I would believe you will need to replace motherboard. Sorry :( 
June 16, 2010 12:34:49 AM

I got my friend's graphics card and put that in, still nothing. So do you think its the mobo? Could overclocking be the cause of the crash or is it just a coincedence?

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a c 122 B Homebuilt system
June 17, 2010 7:22:29 PM
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Corsair doesn't make a 525 watt PSU. Do you mean 550 watts?

carfreak3504 said:

Today I took the whole thing apart, set out the motherboard onto a anti-static bag and plugged in only power, graphics, and CPU fan. Still no beep codes, or post screen

With the system still breadboarded, remove everything except the PSU, CPU & HSF, and the system speaker. You do have a system speaker installed, right? Make sure the CPU power (4 or 8 pin ATX connector) is plugged in.

Try to boot. You should hear a continuous series of long single beeps indicating missing memory. Silence indicates something wrong with PSU, motherboard, CPU, or a missing system speaker (the thing that goes beep).

At this point, you can sort of check the PSU. Try to borrow a known good PSU. If you cannot do that, borrow 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...

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.

Install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card. Silence or long single beeps indicate a problem with the memory.

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.

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.
June 18, 2010 5:38:24 PM

"All the fans rev up, and lights come on, but NOTHING shows up on the screen."

I have the same symptoms. In my X2 system, Gigabte MB after setting affinity for an intensive application it powered off. I think it was in a loop and got very hot and I'm bad but the cooler was acting flakey and should have been replaced.
When powering on no post - beeps. The fans, including the CPU fan spin. I thought the CPU was burned out, but after throwing on an X2 5200+ with cooler = same problem.

I'll try the following next:
1. clear cmos via jumper.
2. Breadboard the mother board as suggested and use a screwdriver to short the power to get it to turn on.
3. Try different power supply. I think if the 4 pin connector near the CPU was bad it would not post and cause these systems.

Good luck to the OP. I feel our pain!
June 18, 2010 6:30:44 PM

rattman169 said:
based on what is written, I would say you may have shorted the motherboard. If you can test each of the other components (Ram, video, CPU, PSU) in another machine to verify they work (each individually) but I would believe you will need to replace motherboard. Sorry :( 


Huh? if the MB was shorted out the fans wouldn't be spinning. It would start for an instant then power off.
a b B Homebuilt system
June 18, 2010 6:39:31 PM

superfuzzy said:
Huh? if the MB was shorted out the fans wouldn't be spinning. It would start for an instant then power off.

Not necessarily. That depends on where the short is occurring on the motherboard. You can't say that the motherboard isn't shorted just because some fans are spinning.
June 18, 2010 6:53:18 PM

shortstuff_mt said:
Not necessarily. That depends on where the short is occurring on the motherboard. You can't say that the motherboard isn't shorted just because some fans are spinning.


I second that notion. I have seen motherboard that are bad, but the fans and HDD spin up... Confusing at first, but replacing the mombo fixed the problem... Blown cap. that managed the memory modules power, another case where there was a blown cap. that regulated the onboard video... Fried cmos chip next to the CPU... the list could go on and on....

June 18, 2010 8:52:38 PM

When I think of a short I associate it with a "hot" part of the MB touching the case. I stand corrected.

Also a "Fried cmos chip next to the CPU" is a possible cause of my problem - unable to post but all fans spinning. The CPU running hot could cause a problem there.
June 21, 2010 12:25:30 AM

what could happen is the intense heat if not properly cooled next to some of these capacitor, boom, some of these capacitors sit right next to CPU and some HSF can go slightly against 1 or 2 and the heat on the metal melts the capacitor, system may not boot but power is still be supplied, so fans spin. I have seen this, sucks big time.
July 1, 2010 12:24:25 AM

So ASUS is sending me a replacement Motherboard, it should be here soon and I'll test it. I'll post about the outcome

Thanks everyone for the help!
July 8, 2010 12:14:27 AM

Well ASUS sent back a motherboard. I opened up the package to find they sent me the exact same board. Did they even fix my board? Still no boot, any ideas?
a b B Homebuilt system
July 8, 2010 12:54:41 AM

try 1 stick of RAM.
January 17, 2011 3:47:45 AM

Best answer selected by carfreak3504.
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