System will not always post

larry86larry86
edited May 2007 in Hardware
Hi all,

Got a small problem that you might be able to help with. After transplanting my system to a new case it has problems posting, I'd say 1 in 10 start ups/re-boots actually loads windows, the others give nothing. Fans and drives power up but nothing more, and no CMOS beeps. When it does post and boot the system is perfectly stable. I think it may be due to the mobo shorting somewhere so I need to run it out of the case. My question is this, is the mobo likely to be shorting as sometimes it boots and is fine, I was under the imression that if it had shorted/was shorting it shouldn't do anything? Also what could be the reason for this tempremental booting/not booting?

Larry

Comments

  • LeonardoLeonardo Wake up and smell the glaciers Eagle River, Alaska Icrontian
    edited May 2007
    If nothing has changed other than the cases that houses the system, your guess about shorting is good. That would be the first logical troubleshooting step. If it were my computer, I'd remove the motherboard and start over, that is, to reinstall the board. Double check all the board standoffs to ensure they are secure and lined up properly with motherboard fastening points, and that all fastening screws fit correctly and are snug. Just a small gap between the motherboard and the top of the standoff can cause a short. Also inspect the case for any loose wires, screws, or what have you.

    Oh...when you migrated the system, did that include the same PSU?
  • larry86larry86
    edited May 2007
    Hi,

    Nah, different PSU, higher wattage (400 vs 350), both were no name, came with the case types, but my system is nothing special (Gigabyte GA7n400-L, AMD 2100+, Radeon 9700 PRO, gig of ram, 160 gb seagate) so it's never ballsed up due to power issues. Could intermitent performance from the PSU be a cause?

    Just to clarify, when you say "a small gap between mobo and standoff" does this mean that they should be clamped together tighly? Will a gap allow space for arcing and shorting? I won't be able to pull it all appart for a while but I've had a look inside with a torch and several mirrors and can see no obvious shorting, but will take it all apart anyway.

    Is there a possibility of shorting taking place but not always resulting in failure to boot and allowing the system to run sometimes?
  • LeonardoLeonardo Wake up and smell the glaciers Eagle River, Alaska Icrontian
    edited May 2007
    The motherboard should rest firmly on the tops of the standoffs. Whether a gap would case an electrical arc or not, I do not know. But I due know that such a gap can interrupt an otherwise good ground (earthing). Given that the majority of your attempted boots are successful, I would not suspect the PSU at this time.
  • larry86larry86
    edited May 2007
    gotcha! My mistake at the beginning, meant to say that the majority of boots are un-succesful. I'll post back with the results of running it out of case, fingers crossed that'll be the end of it all! getting a new system soon but need this one plodding along as a stop gap! If anyone has anything spring to mind i can play with when it's out of the case let me know and I'll give it a bash!

    One last thing, could this also be a CMOS issue? i.e. my fsb and multiplier are resulting in some sort of unstable configuration? or dies the fact that i can sometimes get it up and running negate and possible issues like this?
  • LeonardoLeonardo Wake up and smell the glaciers Eagle River, Alaska Icrontian
    edited May 2007
    One last thing, could this also be a CMOS issue?
    Doubtful. Were it a CMOS/BIOS issue, most likely it would boot the same way every time - either without error or the same error consistently.

    When you pull the motherboard, if you can configure it so, try and boot your system completely outside of the case. Have the board sitting on a non-static surface, such as a block of wood or cardboard. Connect everything as if it were in the case. If it shows the same symptoms, then we've ruled out a case-induced short.
  • GrayFoxGrayFox /dev/urandom Member
    edited May 2007
    Check the board for bad capacitors.

    information about identifying bad capacitors can be found here.
  • larry86larry86
    edited May 2007
    Success!

    Hereit goes, took it all out of the case, set in on boxes e.t.c. with bare minium set up, worked fine, added devices one by one, worked fine. Checked over the offending case and couldn't find any obvious faults. Re-installed all bits in the case, fired it up........ nothing! Out of case again as before, worked fine!

    Remebered that the case in question was a bit cheap and flimsy (only got it cos I could fit more fans in it, unlike my old case!), housing flexed alot and had to really force the graphics card to marry up the the slot in the back. Thought that this might be bending something aronud and causing it to short.

    Re-installed everything in the old case and still nothing. Double checked everything and noticed that some standoffs were a bit loose and one or two mobo screwswere ever so slightly the wrong size for the standoffs. Picked out all compatible standoffs and screws, made sure they were all tight, put everything back in and here I am now typing away!

    Looks like the problem was as you fellas had pointed out, the mobo was shorting to the case but from all my investigating it was not an obvious short. It appears that a slightly loose standoff or two were either preventing adequate grounding or otherwise causing a problem.

    Will never buy a cheap flimsy case again, it's caused me the most stresfull day of work I've ever had!

    Thanks for the help guys and anyone new to this forum business, listen to the people on here and do what they say!
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