On 19 Nov 2006 13:56:01 -0800, "Martin" <(E-Mail Removed)>
wrote:
>I have a problem with a home-build PC that's been running XP with SP2
>flawlessly since Aug 2005.
Ok, but, since this is a hardware group it's always a good
idea to first list your major hardware, and the PSU make,
model, wattage- even better to include the amperage rating
on the most loaded rail which is typically the 12V rail.
I see you did list the system below, but what's this PSU?
Given the symptoms, if this is a generic came-with-case PSU,
it's such a likely failure point that I'd go ahead and
replace it, unless an inspection reveals your motherboard
has failing capacitors.
>
>In the past two or three months it's developed a problem where it
>randomly just reboots itself.
>To begin with it would only reboots very occasionally so the problem
>was not dealt with.
>In recent weeks the PC has taken to rebooting very often so i was given
>the job of fixing it.
>
>First thing i suspected was CPU overheating - BIOS reporting temps of
>approx 65C at idle just minutes (seconds even) after booting from cold.
>I removed the CPU's thermal pad, cleaned both CPU and heatsink with
>spirits and applied a small blob of thermal paste.
>CPU temp now averaging a much more healthy 50C on average - the HSF is
>not a performance model, just an el cheapo, so i suspect that's about
>the coolest it'll run without a better HSF.
>Anyway the reboots continued after the CPU temp treatment so i rules
>out CPU overheating.
Not necessarily, we don't need to know the average temp so
much as the max temp. Actually only the max temp matters,
it is useful to run a stress test like Prime95's Torture
Test, noting what the max temp was (after running at least
30 minutes), AND whether during this test, any errors were
reported by Prime95. The error feedback part is important
as many stress tests won't tell you about that problem.
However, after you redid the heatsink, it's not so likely
the system would be overheating from a cold-off state onto
the point of rebooting so soon thereafter. Unless the
heatsinks aren't making contact well at all, it'll take a
few minutes before they get up to normal operating temp as
the chassis also heats up.
>
>The reboots happen anytime - either when booted into XP or just in the
>BIOS setup mode - so i ruled out any software problem.
If you have a bios health monitor menu page, have you left
it on that page to observe the voltages?
Do you have a multimeter you might use to check voltages?
If so, leaving it connected might allow comparison with the
bios.
>(We did successfully clean install XP 7 days ago, this was when the PC
>wasn't showing any signs of rebooting - needless to say the problem
>continued).
Is it possible something has changed since then? Had the
system been moved, and that stressed some mechanical
connection, or maybe it was placed next to a heater or HVAC
duct blowing hot air? Might it be on a home AC circuit with
other equipment (like a heater or motorized
something-or-other, maybe a frige)?
>
>I removed the AGP card, cleaned the contacts with a pencil eraser, and
>reinstalled it - still the reboots occur.
>(The PC has no PCI cards to inspect).
Ideally you should not clean contacts with an eraser,
because practically all erasers are abrasive and the gold
plating on the contacts is very very thin and soft. Even
so, one time shouldn't kill it, though eventually it'll wear
out the gold and the underlying copper will corrode... over
time, so it's best to clean with a non-abrasive evaporating
cleaner like alcohol or official contact cleaner.
>I removed both memory modules and reseated them - still the reboots
>occur.
>
>Only components left to suspect (other than the motherboard) were the
>two hard drives and the CD-ROM.
>CD-ROM was prime suspect as it's ancient!
>CD-ROM has been disconnected (both IDE and power cables unplugged) for
>the past 5 days - still the reboots occur.
>
>The motherboard's BIOS is the last but one update available for it -
>the latest BIOS update states that it includes a fix for large hard
>drives, one of the PC's hard drives is a 200GB drive so i downloaded
>the BIOS update and decided to update the BIOS.
>The PC has no floppy so i dug out a CDR that i'd made years ago with
>the WinME boot floppy as it's image.
>With that i could boot to DOS and update the BIOS i hoped.
>(The BIOS update and BIOS updater being on a FAT32 partition that i
>hoped to be able to access after booting from the WinME boot CD).
>
>I reconnected the CD-ROM inserted the WinME CD (the PC was booted to XP
>at the time) and as soon as i closed the CD-ROM tray the PC rebooted.
>It then went into a loop rebooting, getting to the part of the BIOS
>screen where it scans for IDE devices and then as the CD-ROM spins up
>it'd reboot.
You might be lucky- if the system is that instable you dont'
want to be trying to flash the bios, the odds are too great
of losing it. Although a bios update can fix logical bugs,
seldom would it be to combat this kind of problem- unless
your bios had a glitch that made it incorrectly detect
hardware temperature and then it was tripping a safety
shutoff threshold, BUT generally that shuts the system off,
not just resetting to a continual reboot... it'd be fairly
pointless for the feature to reset but keep running.
>I removed the WinME boot CD and it booted ok but after less than 15
>minutes started to reboot.
>I disconnected the CD-ROM and again reboots happen.
>
>I then disconencted the 200GB drive leaving it to run on it's 40GB boot
>drive - within less than 15 moinutes it'd start rebooting - so maybe
>the BIOS update with the large hard drive fix wasn't going to help
>anyway.
Unquestionably, the large hard drive fix aspect of the bios
update would not help you with this problem. "Sometimes"
bios also include other fixes or changes not enumerated in
the bios notes, but for a problem this significant I'd
expect there to be a primary listing of this correction.
>
>I'm now suspecting the PSU is the cause - a power drain surge as the
>CD-ROM spins up may explain them reboots. The fact that the reboots
>happen with the CD-ROM disconnected indicate that the CD-ROM itself is
>unlikely to be the cause.
Agreed, PSU is the prime suspect.
>
>The PC is a homebuild with a cheapo case and an el cheapo unbranded
>300W PSU.
Ok but there must be some kinda label on it?
You might unplug it from AC for a few minutes then open it
and inspect it. I'll randomly guess that it's capacitors
have failed.
>It's worked perfectly from August last year up to about 10 weeks ago
>and the reboots happen more and more.
>
>Here's some technical details about the PC:
>Foxconn K7S741GXMG motherboard.
>Sempron 2400+ CPU.
>2 x 256MB DDR333 DIMMs.
>Connect 3D Radeon 9550 AGP card.
>200GB and 40GB hard drives.
>CD-ROM.
>
>BIOS 'PC Health' screen reports these voltages:
>CPU core - 1.58v
>+3.3v - between 3.21v and 3.26v averaging about 3.24v
>+5v - 5.15v
>+12v - 12.32v
>
>What do you all think then?
>
>The PC's owner hopes to add a DVD writer sometime soon so i reasoned
>that a new PSU would not only (hopefully) fix the reboots but also
>prepare it for another device that'll be more watts of power.
Since the system already has upgrades planned, it seems a
good idea to replace the PSU even if it isn't the immediate
problem, as it's likely to be later if not yet... but odds
are good that's the problem.
Similar Threads
