computer quit, couple questions

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I left for work today, and the computer was on and running fine. When
I got home, the fan was running, but the power light was off. Pushing
the button did nothing. Since it wouldn't reboot, I un plugged it and
plugged it in again. The fan will run if the button is held in, but
nothing else happens.

I have a computer friend who can come look at it for me, but I know he
tends to go overboard on upgrades and stuff. I just want to get it
functional again, if possible. I'd like to get an idea of what could
be causing this, and whether it is expensive to fix. I bought this
computer used last sumer for $150, so if it is too much to fix, I will
just loko for another used computer.

I doubt it is the power button since it was on when I left for work.

power supply - I assume this shouldn't be too hard to replace if need

motherboard - if this is toast, would it be worth replacing? Would it
be a huge hassle if I want to keep the rest of teh system and have it
working th to get a new motherboard and hook up all teh old stuff to
it? Or would it require a lot of tweaking to get it working well

CPU? If it died, would it produce these results? Are they spendy? Easy

Hard drive? It would still run if the hard drive died, right? Is this
likely to be the problem? I haven't backed up the hard drive in a
couple months, and I am praying this hasn't been damaged. I did a lot
of work on the computer this past month. (I've learned my lesson).

I do see a lot of dust built up. I will take it oustide in the morning
and give it a good cleaning with compressed air. I suspect this won't
solve the problem though.

Any recommendations of what to check?

Re: computer quit, couple questions

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First thing to check is all your cables - make sure everything is plugged in
OK. Possible remove and re-insert all cables and connectors. Make sure the
RAM is in the slots properly + make sure the CPU is in properly and the
heatsink hasn't come loose. I doubt if any of this will make any difference,
but something could just have worked loose and it costs nothing to check.

If that doesn't help, then you can assume that something has 'gone'. Check
the capacitors on the motherboard - the little cylinder things near the CPU.
If they look all shiny and 'normal' shape then they are probably OK. When
you press the power button, listen to the hard disk to see if it spins and
watch all the case fans and see if anythnig moves - this will tell you if
the power supply is putting out 12v or not. The fact that a fan is spinning
suggests to me that the PSU is not dead, so I would tend to suspect the PSU,
CPU, motherboard or RAM.

Tell us what happens when you try the above things and tell us which parts
of the PC seem to do anything when you power on. Does your CD tray eject for
example? Is there a red light on your motherboard? What fan / fans spin?

Re: computer quit, couple questions

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Last night, the DVD light would pop on for a few seconds, and the fan
on the CPU would run if the button was held. Nothing else.

Today, the fan won't run, but something else does. I'm guessing the
power supply fan. It runs now as long as it is plugged in, don't have
to push the power button. My friend is going to come over after he
gets off work.

I hope it is not the ram. I upgraded that a couple months ago for
$200, and I sold the old ram.

I did give it a good dusting with compressed air. It was really dirty.
So, something may have gotten clogged and burned out.

Hopefully, I will know in a couple hours.

Re: computer quit, couple questions

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Without examining the machine, there is not enough information here to
identify remotely what is definitely the problem.

When you pressed the power button on the PC, things started to work before,
now the power button doesn't make any difference. I can't be sure, but
sounds like the power supply is OK, but the motherboard is possibly not.
When you press the power button on the computer it 'shorts' a connection on
the motherboard and turns the power on to the whole machine. It sounds to me
that this process is not working properly - if the PSU fan is spinning, then
it could be providing power to the motherboard, which in turn does nothing
as it is dead. On the other hand, the motherboard might be fine and the PSU
might be goosed, hence the power button slowly doing less and less everytime
you try it.

Definitely worth having another PSU standing by if you have one - why not
try it yourself before your friend comes round - there is only 1 plug to the
motherboard and one to each drive/device. That way, if you fix it before he
arrives, you can just both sit around and drink beer and admire your work.

Re: computer quit, couple questions

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We tried the one from another similar model. No difference. It is
completely dead with both power supplies. We went ahead and put my
hard drive in the other computer and rescued my files.

Re: computer quit, couple questions

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If nothing happens when you press the power button, then its probably new
motherboard time!

Re: computer quit, couple questions

On Thu, 22 Mar 2007 10:44:09 -0000, "GT"

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First unplug everything nonessential, keeping only video, 1
memory module, CPU & heatsink/fan, then clear CMOS with AC
power disconnected.

We don't know what "one from another similar model" means
though, there is a possiblity the replacement PSU is merely
unsuited for the system.

Re: computer quit, couple questions

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We didn't remove the CPU, but we did the others with no change.

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Same brand, same age computer, slightly different model.

Re: computer quit, couple questions

With those symptoms the odds are that either the power supply unit and/or
the motherboard has died.  The easiest thing to check is the PSU by
replacing it with a known working one of adequate power output.



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Re: computer quit, couple questions

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Do most computers use similar PSUs? I have an old tower that I don't
use anymore. Would it be worth digging out?

Re: computer quit, couple questions

 On Mar 20, 8:42 pm, ""
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  Your every response is based upon "I feel it is this; so it must be
this".  Instead elicit useful replies.  That means numbers.  Let's
start with perspective.   Something called an Ipod is complex and
expensive.   An item much simpler as to be even sold in K-mart for
$20; get the meter.  Two minutes with this procedure answers your
questions immediately or provides data that provides useful,
definitive, and specific actions.  Do procedure in  "When your
computer dies without warning....."  starting 6 Feb 2007 in the
newsgroup  at:

  There is almost nothing visual that tells us anything useful.  For
example, fans can spin; lights illuminate; and power supply is 100%
defective.  Either the power supply is good or bad.  Only way you can
get that answer - two minutes with a multimeter.  Only useful
alternative involves equipment tens of times more expensive.  And
don't disconnect anything.   Disconnection may only exponentially
complicate your problem.

Re: computer quit, couple questions

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Sorry to be a problem. I was hoping to determine whether it was worth
digging out the computer to be available when my friend came to look
at it. I would assume he would bring the meters since that is not
something I know how to do.

As it is, he brought a power supply with him that was not compatible.
My old one was too old. So, I borrowed my nephew's computer, and we
tried that power supply. No change.

Most likely problem is the motherboard, so I can either spend about
$50 and hope it all wokrs together well, or I can just upgrade. He was
able to put my hard drive into the other computer as a slave and let
me copy off the important files onto my external drive.

I'm sorry to have not been specific enough. Unfortunately, until I
have experience with a topic, I don't always know what to ask, or what
information is the most useful. That is why I searched for similar
topics and asked questions.

Next time, I will know what to do.

Re: computer quit, couple questions

  The meter is so 'complex' as to be sold in Kmart.   Using an Ipod is
significantly more complex. Driving a car - far more complex.  Get a
meter because even 12 year olds use them once unfounded fears are
eliminated.  Meters are sold in Radio Shack, Sears, Wal-mart, Lowes, K-
mart, and Home Depot ... because only geniuses can use them?  Lose the
fear to learn.

  Most certified computer techs don't even know how electricity works
- just another reason why so many computer techs can only shotgun and
don't own a meter.

  Meanwhile, you have zero reasons to suspect a motherboard.  No
numbers?  Then anything 'suspected' is wild speculation - also known
as junk science.

  The meter is cheap.  It provides definitive answers that even the
'replacement' power supply cannot provide.  When you post those
numbers here, then useful information may then 'appear'.  Knowledge
well beyond computer repair is demonstrated.

  Get the meter.  You may end up teaching your buddy something useful.

On Mar 21, 12:05 am, ""
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Re: computer quit, couple questions

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I'm sorry that I am so stupid. Without directions, I would not know
what I am supposed to test or what the numbers I am supposed to get
for good results.

As it is, I am satisfied with the results my friend got. He has been
building his own computers for over 20 years, is familiar with the
tools (and does know how to use a meter), and he looked at the
computer in question.

Again, I am sorry to have bothered you. I was not looking to become an
expert, just learn what questions to ask. I have learned my lesson and
will move on. Thank you for the education.

Re: computer quit, couple questions wrote:
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No need to kow-tow to Tom's superiority, man. My recent problems led me
down the same path, and I picked up a meter to do some testing. Well,
the instructions for it were horribly written and assumed a significant
knowledge of electric circuitry. Figuring out how to even set the thing
up to test anything was almost beyond me. The information I could find
on the web was very limited, but what I did find there were plenty of
warnings about the dangers of tyros digging around in hot circuitry with
these things. And Tom provides only enough information to make you
dangerous. I'm sure one can determine if a power supply is good with one
of these, and more about the mobo as well, and I do want to explore its
use further, when I have more time. But right now Tom's
apparently-habitual approach to the whole thing with the totally
uninitiated strikes me as quite irresponsible.

Just my opinion...

Re: computer quit, couple questions

Mark N wrote:
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Oh come on now.  Any moderately intelligent educated child of 10
should be familiar with Ohms law, and everything else follows
naturally.  Add in "voltages under 48 don't bite".  At some point
that child will learn that inductive circuits can generate higher
voltages. :-)

Chuck F (cbfalconer at maineline dot net)
   Available for consulting/temporary embedded and systems.

Posted via a free Usenet account from

Re: computer quit, couple questions

Mark N wrote:
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To give a little more help, than Tom might be comfortable giving, here
is a meter primer. HTH.

******* Using a multimeter *******

The multimeter has lots of ranges and inputs, but you can use just the
ones that are easy to understand to start with. For example, my multimeter
has a "transistor beta" feature, where you are supposed to stuff the leads
of a transistor, into a bunch of tiny holes on the face of the meter, and
I've never used that feature. Maybe it is in the manual, but I've never had
need of it. Since I don't need it, I don't touch it. No big deal.

This meter has four holes on the front, for meter leads. Everything is
referenced to the "Common" or COM terminal. In this picture, COM is in the
lower right corner, and usually is black in color. You can start by plugging
the black test lead into the COM hole. That is your reference point that the
meter will measure the voltage with respect to.

The two on the left are for measuring current, and can be ignored.

To start with, you want to try simple things, like measuring voltage.

The red lead plugs into the "Volts, Ohms, Diode Test" hole. The
black goes to the COM hole. You can probe with the meter, while it
is in volts or "voltage measuring mode", without much danger. If you
plugged the red lead into one of the current holes, and dropped the
meter leads on a live circuit, that would be a close to a dead short,
so you have to be a bit more careful with the current functions. And
the dead short in the current measuring ranges, is present even when
the meter is turned off. So just keep your red lead out of the "Amps"
or "Milliamps" holes for now. In fact, I seldom use the "Amps" or
"Milliamps" holes, and the test leads stay in the same two holes (on
the right) almost all the time.

OK, with the leads plugged in, you select a safe operating range.
Meters can be "autoranging" or "manual". Mine is manual, because
I like them that way (they respond faster to changes). I've also
used plenty of different autoranging meters, and they're fine too.
If I was working in a PC, and the scale on the meter offered 1000V,
200V, 20V, 2V, 200m as options, I would select 20V range. That is
because the most positive and negative voltages expected on a PC are
+12V and -12V. Both should be readable within that range. Since I've
also recently been measuring the A.C. voltage in my house, I use 200V
for that, since my house voltage is supposed to be 113VAC or so,
according to Hydro.

So, we've plugged in the probes, set the meter to 20V. Well, what
function do we want ? It would be Volts DC, because direct current
or DC is what comes out of the PC power supply. VDC means we
are expecting a "flat", "non-varying" voltage. (AC, like my house
power, is time varying, and I'd select the volts A.C. function for

Once you selected a range which is slightly larger than the thing to
be measured, you can switch on the meter. For volts ranges, zero is
the normal, unused reading. On ohms, the meter basically shoots
offscale, and would give an overrange indication, and the display
might flash. But for volts, we get a calming zero value, that won't
jangle the nerves.

When working in the PC, you really don't want your hands full. You can
buy alligator clips at Radio Shack, and I have small ones and slightly
larger ones. The small ones snap onto the tips of my meter probes
(after some bending with pliers :-) ). You can also get meter leads with
an alligator clip already on the ends. Using an alligator clip, I clip
the black meter lead (COM) to a screw on one of the I/O connectors
on the back of the computer. By doing that, I only need one hand to
make measurements. The screw on the I/O connector is at ground

Using the red lead, you probe where you want to measure a voltage.
It may take the meter several readings to settle down. If I was
reading the 12V rail, I might see "+12.23", which means I made
good use of my meter's output digits. If the display read "  12",
which is what I'd see on the 1000V DC scale, I'd know to increase
the sensitivity of the meter, by selecting the next range down,
which is 200V. Then I'd see "+ 12.2". And finally, when I select
the 20V scale, I'd see "+12.23", which is all the digits my meter
has got.

The power supply has a label on the side, which will mention a number
of useful things. It might tell you the expected uncertainty of its
output voltages, like +/- 5%. On the 12V rail, the expected voltage
ranges would be +11.4 VDC to +12.6 VDC. The +12.23 value I just
measured, is within the allowed max and min value, so the supply is
working within spec.

So, that is a basic measurement, and how to interpret it. On my meter,
I have one set of knob settings, that select 1000V, 200V, 20V, 2V etc,
and a separate push button selects between VAC and VDC. Some meters have
separate knob areas for the volts DC and volts AC. So selecting VDC, which
is what you want for checking the outputs of the PSU, may vary from
meter to meter. And with a cheap, "super autoranging" meter, you
may have very few knob options indeed on the meter. It might just
say VDC, and do all the work of measuring the voltage for you. The
meter in that case, keeps adjusting the display, and the decimal point,
until the meter makes good use of all available digits on the display.

Note that the meter has limited accuracy. For example, my meter has
a "3 1/2 digit" display, which reads from 0 to 2000. But the spec for
the meter, notes that it is 1.5% accurate. That means, when I measured
the "12.23" value above, the _true_ value could be anywhere from 12.05
to 12.41 volts. Which means the least significant digit is pretty useless
on my cheap meter. So when making the measurements, you still have to
keep the measurement qualities of the instrument, in perspective. The
instrument is probably not going to be quite as bad as the 1.5% number,
but it could be.

To access motherboard voltages, the 20 or 24 pin shell on the
connector, is open at the back. You should be able to touch the
metal contained within each nylon shell hole, with your red probe tip.
That is how you can measure all the rails, while the fans are spinning
on your rig. Naturally, it is easier to work on a PC, if you
disassemble it and put the guts on your work table. That makes it
easier to see what you're doing, and makes it easier to probe in
just the right place with your new multimeter.


The main danger inside the PC, would be shorting something. If I made
an accidental connection between +5V and GND for example, the wire
I used to do it, would got hot, so hot that it might burn me. The
circuitry could get damaged. But that is about the extent of the danger
to a human - short of taking a bath, and dropping the entire PC
in the bath with you, the risk of electrocution is minimal, since
you aren't working with the AC voltages from the wall plug. (You'd
have to do something extremely stupid, like jam a screwdriver tip through
the metal housing of the PSU casing, to get a shock from the AC. So
don't do that :-))

Anyway, have fun,

Re: computer quit, couple questions

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  Meter is so easy that a caveman can do it.  Why so little
information about using a meter?  Why post what even a 12 year old can
do?  Dangers?  Only danger inside a PC is inside a box with warning
labels.  That box that says "Keep out" is called a power supply - for
those who like to be cavemen.

Re: computer quit, couple questions

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I didn't know they had multimeters back then!

Re: computer quit, couple questions

"w_tom" wrote:
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Tom, you really are a dick, aren't you? So someone with no idea what
they're doing can't possibly damage their system with one of these
things? Not what others are suggesting, and not what common sense
dicatates. And the meter I got has instructions that look like one of
those typical butchered direct translations from Chinese to English,
really pretty much worthless. And to get people to dive in without
sufficient care and knowledge, you resort to mocking insults and
putdowns - either one should be able to figure it out or one is an
idiot. Well, thanks for all the help...

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