intermitent computer problem. wont switch on.

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View

I am so pissed off with this whole thing its not true, but here goes.
I have a media center with the following spec:
athlon mobile 2600
abit kd7 raid
768mb ddr ram
40gb laptop hd
dvd writer
radeon 9600
black gold tv card

All was fine up until a couple of weeks ago.  I switched it on one day
and it took ages to get into windows.  When it did it complained that
it couldnt get an ip address and that i had limited networking.  the
usual green and yellow lights that are just by the ethernet port on my
motherboard werent lit.  So i switched it off and then back on again
and all seemed fine.

Next time i turned it on, it did nothing, no power, lights nothing.  so
i turned it on and off at the mains a few times and then it seemed ok.
however on some of these attempts the networking lights did not come
on.  So it got worse and worse and then most of the time just wouldnt
switch on.  i took everything out of the case and unplugged stuff.
Nothing really made any definite difference so i figured it was either
a faulty motherboard or psu.  So i bought a new asrock motherboard.  It
was a bit rubbish (didnt go into standby amongst other things) so i
sent it back and got an asus a7n8x-x.

this bizarrely wouldnt come out of standby and sometimes wouldnt go
into standby.  so i gave up and bought an identical board to the one i
thought i broke (abit kd7 raid).

Plugged it all in this evening, same problem.  gutted.  so i figured it
must be the psu.  i borrowed one from a friend, same problem.  so i
have spent the evening trying to work out what is wrong.  this is what
i can deduce:

the networking just refuses to work no matter what i do.

changing something  major like pulling out a pci card (my tv card)
makes it work (powers on fine etc).  then it will just stop working a
few minutes later if i switch it off.  if i put the card straight back
in it still works.  this major change can be pulling ram, putting it
back in, changing the hard drive from primary to secondary, anything
like that.

I have tried taking everything out but it makes no difference.  there
isnt a single specific thing i can do to make it work or not work,
every time i can make it work or not work by changing something else.
its so bloody intermitent!!

i thought perhaps it might be a shortcircuit or not being grounded
properly as sometimes moving the psu from inside the case to outside or
vice versa can fix/break it.

can someone please help me!

Re: intermitent computer problem. wont switch on.

Quoted text here. Click to load it

When you installed the brass standoffs in the motherboard tray, were
you careful to only install standoffs where there are corresponding
plated holes in the motherboard ? If a standoff just touches an
area of motherboard that doesn't have a matching hole, the standoff
can short to some tracks. The short can be intermittent, and every
time you pull or push components into the motherboard, the symptoms
can change.


Re: intermitent computer problem. wont switch on.

On 23 Feb 2006 16:04:46 -0800, "Kevin"

Quoted text here. Click to load it

I suppose it could be a symptom of another problem, but
could as easily just be a simple network problem like the
jack not seating well in the network socket.  Maybe you do
only have one problem further detailed below but consider
there might be two or more minor problems as well, not
necessarily related.

Quoted text here. Click to load it

What power supply make/model/wattage?  Does this system have
limited airflow?  How long has it been set up, how many
"on"-hours and the general load while on?  A low-airflow
system running at continual load (like encoding video) may
wear out certain parts faster, like the motherboard or PSU
capacitors, make even caps on the video card in some special
SFF cases.

Quoted text here. Click to load it

Forget about the networking for the time being, just unplug
the cable.  Get back to it after rest of system seems ok.

Quoted text here. Click to load it

Standby issues could be bios or component drivers, you
might've checked on updated versions of each.  Not going
into standby is more puzzling, I'd wonder if something
running in the background was preventing this and it's just
coincidence that "going into standby" and "coming out of
standby" are related by the common theme of "standby".

Quoted text here. Click to load it

Which same problem?
What power supply (borrowed)?  These boards you mention may
have slightly differing power requirements.  I don't know
about the Abit or Asrock but the Asus board uses 5V for CPU
power ... it's likely at least one of the two others if not
both use 12V for CPU power.  This means that unless you had
a fairly high wattage, quality name-brand power supply, the
same power supply would not be suitable for both conditions.
While your system is not overly power hungry by modern
standards, some name-brand 300W or most generic 450W PSU
could be marginal for it.  While the condition might not be
revealed by voltage measurements, those measurements might
be a good start at troubleshooting.

Quoted text here. Click to load it

Is it a direct shot to the other end of the cable?  Check
the other end, the jack, swap another system to that jack
and see if the jack on the (switch or router or whatever...)
is working properly.

Quoted text here. Click to load it

How about just unplugging it from AC and changing nothing?
Had you changed any bios settings?  Try clearing CMOS and
manually underclocking the board(s), does that improve the
successful-power-on ratio?  Some boards seem to get confused
about Mobile CPUs too, they'll work but seem temperamental
in starting up.  Do your boards officially support mobile
CPUs?  Have you updated their bios recently?  Do you have a
spare non-mobile CPU you could try?  Unless the power is the
problem, it could be that you have different problems with
these different boards.

Quoted text here. Click to load it

Check all the boards' batteries too, even on a new skt.A
board today, it may've been sitting on a shelf running off
the battery the whole time.  A marginal battery can cause
this but often shows other symptoms like loss of system
clock time or messages like loading defaults or other
similar loss of settings.

Too many variables to consider at this point, I'll cut the
post off here until more info like the PSUs used.

Re: intermitent computer problem. wont switch on.

thanks for your replies guys.
paul: yes the brass standoffs are all in the correct place, i did
double check this as i thought it might be a problem.  also when i run
the motherboard outside the case the problem is still there.

kony:  sorry, i forgot to post about my psu.  it is an akasa 460w.  the
third one down on this page:
so its pretty decent.  the other one i tried was a generic 235w one.
as its a media centre, it generally isnt doing very much, just playing

all the motherboards had the latest bios and drivers.  i have found it
difficult to get pcs into proper s3 stanby modes before, but i managed
it on the original kd7 board which is why i then bought an identical

the cpu is underclocked anyway, but i have tried fidddling with the
multiplier, fsb and voltages.  all of which make no difference.  the
kd7 board doesnt officially support the mobile athlon but it was
running fine for almost a year before these problems started.
unfortunately i dont have another cpu i can try.

the networking is plugged into a wall socket which goes to the router.
i have tried using a different socket which i know to be fine, and also
a crossover cable.

i'm pretty sure its not a battery problem as it doesnt show any other
symptons as you say.

turning it on and off at the mains does cure it sometimes, but very
rarely and only after dozens of tries.

its true, the problems with each board could be unrelated and also that
it could be two small problems causing it.  the cpu is really the only
thing that has not been changed in all my tests.

I just turned it on this morning (it has been turned off at the mains
all night) and it has come on fine even with the two ethernet lights on
and working.  i bet if i had left it turned off, but on at the mains it
wouldnt have started.  Im so sure its a short/grounding issue, but i
just cant figure out where or how.

thanks again for your replies, they are much appreciated.

Re: intermitent computer problem. wont switch on.

turned it off and it wont go back on again.  i'll leave it switched off
at the mains all day and see if it works this evening.

its almost like (and im no electrical engineer) a capacitor or
something has to be completely discharged  before it will work.

Re: intermitent computer problem. wont switch on.

oh and also my psu has recently started making that very high pitch,
quiet 'squealing' noise that not everyone can hear.  i think it pretty
much started when this whole thing started.

Re: intermitent computer problem. wont switch on.

interestingly i'm not the first person to have this problem: / / / /

Re: intermitent computer problem. wont switch on.

On 24 Feb 2006 01:41:27 -0800, "Kevin"

Quoted text here. Click to load it

With any semi-popular motherboard, you'd be bound to find
several people who have systems not working properly.  Maybe
there's a problem with the board, certain revisions or maybe
not, maybe that's just par for the course and you'd get same
number of posts with other board with same user base.

You'd switched boards though, so it's a bit hard to nail it
as being a board problem.  If as you wrote, the PSU started
making different noise roughly about the time the problems
started, I'd measure the voltages and try another PSU.

Re: intermitent computer problem. wont switch on.

Kevin wrote:
Quoted text here. Click to load it

That certainly sounds suspicious and the 235W unit you previously mentioned
having tried may not have enough power to reliably spin everything up.

Site Timeline