Installed new cpu and MOBO - power constantly on / wont do anything

By pauldoherty ยท 9 replies
Oct 8, 2005
  1. Hi there,

    I am not an expert, but i am fairly competent on most things - here's my problem.

    I recently took a look at a relatives pc. It kept resetting before windows would boot up. I had someone look at it, and put it down to a mobo / cpu problem.

    As it was socket A, I decided to change both, and opted for a sempron 2600+ cpu and a asus (HP) k8n8x mobo. After installing the new mobo (with both 20 pin and 4 pin connectors) and processor, i installed the video card, 512mb ddr 3200 ram, hdd and connected the monito and the mouse (usb) and keyboard (ps2). Once i plugged in power lead the board powered up but no signal went to the monitor, nor to the keyboard, although mouse powered up.
    All fans power on, all drives, cpu heats up - but no matter what configuration i use to connect the power switch and othe led cables the pc gets power as soon as you plug in power cord, and the buttons don't serve any function.

    As for system beeps - i wouldn't know, as there doesn't seem to be anywhere to connect the speaker to on the motherboard.

    I am losing the battle here, and i would really appreciate it if anyone could give me their feedback to assist me along. By the way the psu is 250W.

    Thanks in advance
  2. Merc14

    Merc14 TS Rookie Posts: 171

    Welcome aboard Paul, hopefully we can help. First things first, when you change out a motherboard (mobo) it requires, under most circumastnces, that you do a complete, fresh install of windows. Sometimes windows will accept a new mobo and CPU just by loading the new drivers but then there are a multitude of little problems that plague the user forever.

    So a few questions:
    1. Did you reload windows after fully formatting the Hard Disk Drive (HDD) or just plug the HDD in and load the new drivers?
    2. Did you install this in a OEM (Original Equipment Manufacturer) type case (like Dell or HP) and if so is this the original Power Supply Unit (PSU)?
    3. What kind of video card are you using?

    If this is in a Dell case as an example then that may be the problem as their cases are not wired like others.
  3. pauldoherty

    pauldoherty TS Rookie Topic Starter

    Thanks for replying. I haven't got a chance to reinstall windows as i can't even get into the bios due to lack of communication between pc and monitor. The graphics card is an elsa gladiac 511 (rest of the details in profile)

    Hopefully I am missing something here - but I am simply plugging in the old hard drive (with old data) into new mobo. Although i have tried powering up without any drives attached but still nothing from the monitor. I have also tried an abit radeon r9250 graphics card (brand new), but no difference.

    I assumed that if you connected mobo, cpu, power, ram, graphics and powered up you should at least see the bios appearing on the screen. I have also tried clearing the cmos.........
  4. pauldoherty

    pauldoherty TS Rookie Topic Starter

    Sorry, i forgot. Regarding the case , I think it is an MSI c/w 250w psu. It was bought by person who built previous pc a couple of years ago.
  5. Merc14

    Merc14 TS Rookie Posts: 171

    DId you use standoffs when you mounted the mobo? They keep the mobo from touching the metal of the case. If you did then there is something mechanically wrong as you should be able to get into BIOS as you said. You are going to have to do a barebones setup and test each component. This will read a lot harder than it actually is. The initial procedure takes only around 10-15 minutes. The follow on troubleshooting may take a lot longer though. Also, please do not skip steps. Do everything in order and as listed or your troubleshooting will be flawed.

    Caution: Please remember that turning a PC off does not mean there is no power going through it. Modern systems maintain a trickle of power to keep the standby functions running. You either have to turn off the switch on the Power Supply Unit (PSU) itself or unplug the system from the wall. Unplugging is best. If you have a LED on the mobo that is lighted all the time. make sure it is out before proceeding. Also, be aware of static. Make sure you wear and ESD strap or discharge yourself on a steel part of the case before touching anything inside.

    First, unplug the PC from the wall and then open it up. Disconnect all the drives (floppy, CDROM, DVD etc.)from the motherboard (mobo) and also disconnect your Hard Drive(s) from the mobo. Do not leave the hard drives connected. The system will boot into BIOS just fine with no hard drive attached. Unplug the power from all those drives you disconnected from the mobo. Remember to disconnect the front panel firewire and/or USB ports.

    Next, remove all the RAM, except for one stick, from the mobo. Some mobos are very picky about where the RAM needs to be placed so make sure the one stick of RAM is in the correct slot as per your manual.

    Now you are stripped down to a barebones system. The PSU, the mobo itself, 1 stick of RAM, the CPU/HSF and video card. Reset your CMOS/BIOS while the system is stripped down, unplugged and open. You do this by removing the battery and then moving a jumper near the battery around. Usually there are a set of three pins with two covered by a jumper. You move the jumper from pins 1&2 to pins 2&3 and let it set for a few minutes then reset the jumper to pins 1&2 and replace the battery. CMOS and BIOS will be back at default settings after doing this.

    Now check that everything is seated correctly, both the 4 pin and 20 or 24 pin power is connected and secure and if so then plug the PC back into the wall and make sure that any LEDs that should be lighted on the mobo are lighted. If all is still well then turn it on. Hopefully she boots right back into BIOS.

    If you get back into BIOS you can start troubleshooting by turning the PC off and unplugging it and reconnecting peripherals one at a time. The idea here is to connect and reboot until something hangs your system up This presumably is the bad piece of gear.

    If you cant get into BIOS and have the same problem as before then you know it is either the PSU, the RAM, the CPU, the mobo itself or the video card. Change out each these until you get into BIOS. I would start at the PSU as it is usually the guilty party in a situation like this and is also easy to change in and out you are down to just 2 plugs now remember). Next up would be the video card and/or RAM and if still no luck then things get hard as you now have to consider either the CPU or the mobo.
  6. pauldoherty

    pauldoherty TS Rookie Topic Starter

    I have tried everything, even benchtesting the mobo and just connecting ram, video, keyboard and cpu - stil no signal to monitor.
    On this mobo, there doesnt seem to be anywhere to connect the internal speaker, therefore i am not getting any beeps to diagnose.

    On the original problem of the power always on - I have noticed that the power goes straight on when you plug in power cord, but you can turn it off by holding power button for 5 secs, and of course you can turn it back on again.

    Back to the drawing board.....
  7. Shadowrunner

    Shadowrunner TS Rookie Posts: 106

    man 250 watt couldnt power anything almost -- those shuttle cases use those. i say get a bigger power supply. a power supply is something you dont want to go cheap on
  8. pauldoherty

    pauldoherty TS Rookie Topic Starter

    I connected power cord with cpu, fan and keyboard only. Got beeping in threes continuously.
    I am concerned with the lack of power to the keyboard - if i unplug it and plug it in again, the 3 lights flick on then staight off as usual, but the num or caps lock lights dont come on when relevant button is pressed.

    Guys i know this is a pain in the ***, but i am tearing my hair out - please help.
  9. DX1

    DX1 TS Rookie

    I had this same problem when I installed my first Motherboard, i forgot to use the standoffs and I fried the motherboard, luckily that was the only thing that was wrecked. I hope this isn't the same problem that you have but it does sound like the exact same thing that happened to me. Hopefully you get things sorted out.

  10. pauldoherty

    pauldoherty TS Rookie Topic Starter

    there's the 3 brass (i think) nut spacers at the back of the system, and then the 3 plastic lugs that the mobo clicks into on the other side.

    Am i right in thinking that if this was the issue - if i took the mobo out and insulated it by placing it on a piece of cardboard it would resolve it - only for test purposes of course?
Topic Status:
Not open for further replies.

Similar Topics

Add your comment to this article

You need to be a member to leave a comment. Join thousands of tech enthusiasts and participate.
TechSpot Account You may also...