1 yr old Homebuilt computer now having issues

So I built a new system almost a year ago and has been running great until earlier this week.
A couple days ago I tried booting up my system and the fans would come on but the system would not post. I tried almost everything I could think of, and finally swapped the PSU with another one from another machine (this PSU was working great).

Now while I tried finding a replacement for PSU#1, I was using PSU#2 in my system with no problem, however today I tried starting up my system, and the system did not POST - this time it kept cycling on and off, as if the new PSU didn't have enough juice to start up the mobo.

I was looking for some help with this, am I just having bad luck and both PSU kicked the bucket the same week or am I missing something else?

Any help?

System -
Core i5
ASUS p7p55D
ATI 4850 512 MB
2 x case fans

PSU#1 originally from this machine - OCZ 550W
PSU#2 from other machine - enermax 485W
7 answers Last reply
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  1. I dont think that the PSU's are the main problem here. That hardware should be ran fine with both of them, combined with the fact that the fans still work. That is just my opinion, though. It ran fine for how long with the enermax PSU? Did you try the OCZ PSU with the other system?
  2. The enermax PSU was used for about 2-3 days with normal use

    OCZ PSU was tested with another system and was unable to boot that system in any case

    Interestingly enough - I took out all the components and reassembled them again and it seems to have done the trick (Did not remove ram or cpu/heatsink, just disconnected all drives, took mobo out of case and reset back into case after adding 2 more standoffs and screwing the mobo back in)

    any ideas? the enermax PSU is now powering the machine, but the OCZ is still unable to get any system to POST - so is the OCZ the problem, or something with my system affecting the PSU?
  3. ^ Yeah, looks like the OCZ PSU is the problem. You can try running again with the OCZ and see, but I do believe the OCZ is dead.
  4. I would like to hope so, but that doesn't explain why my system was cycling on and off with the new PSU (enermax) - could it have been a grounding issue with the mobo on top of a PSU that kicked the bucket?
  5. ^ You DID use the stand offs right?
  6. yeah I did use the standoffs - but now the problem is back with the PSU that was working. It worked for a day, with multiple shut downs and boots, and then 24 hours later the same symptoms of cyclical boot up and shut down with no POST - booting up last less than a second
  7. Tear it down and breadboard the system.

    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.

    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.

    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.

    This will be a little different if you have integrated graphics.

    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. 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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