Computer will not POST

I turned on the computer and wanted to select the boot device by pressing the F12 button (I wanted to get into Ubuntu again from a CD), but instead of getting the list of booting devices, I got some weird characters on the screen and the computer froze. So I turned it off and back on, and now my computer will not do anything, no post, no motherboard sounds. Only sound comes is from all the fans operating and the fan from the video card starts running at full speed and stays like that the whole time. If I press the Power button on the front of my computer it stays on, to turn it off, I have to go to the back of the computer and turn off the Power Supply switch. Is this a bad PSU? a bad Mobo?

These are my specs:
Motherboard: Gigabyte GA-MA790XT-UD4P
Processor: AMD Athlon II X4 630
Memory: 2Gx2|GSKILL F3-12800CL9D-4GBRL
Video Card: 2 XFX ATI 5770 Crossfired
I have tried switching the video cards and nothing happens either. Any help would be appreciated.
8 answers Last reply
More about computer post
  1. Try re-setting the bios.
  2. Already tried:
    -Re-seating the CPU
    -Resetting the CMOS
    -Re-seating the Memory and the Video Cards
    -Using only one memory stick and try it in every bank, then switching to the other.
    -Switching between video cards.

    None of them worked.
  3. Have you tried re-setting the bios by removing the bios battery for15 mins as well as the jumper.

    Have you tried removing the main 20/24 pin atx cable, draining system and plugging back in?
  4. I tried removing the battery and jumper.

    As for the other what do you mean by draining the system?

    Thanks for your help
  5. Just pushing the power button a few times while unplugged.

    Have you tried unplugging everthing that isn't needed to boot and firing it up.

    You are 100% sure the bios jumper is on the right pins.
  6. right now I have everything unplugged except for memory and video card.

    There are no bios jumpers...only the ones to clear the CMOS. If I am no longer getting the motherboard beep sounds indicating an error, does that mean it is dead?
  7. System specs also include the PSU.

    Work through our standard checklist and troubleshooting thread:
    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.

    I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different.

    Breadboard - that will help isolate any kind of case problem you might have.

    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.

    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 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.
    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.
  8. Thanks. Will go over it and update.
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