PC hangs with cover on, doesnt hang with cover off! bizarre

[Colm Ward]

Hi

I have a bizarre problem with an old (but still useful) Dell Optiplex
which I've been given. It's a 166MHz with 128MB RAM.

If I boot (Win NT), after something between 2 and 25 minutes the
machine will hang and wont boot up again at all until I switch it off
and give it maybe half an hour to "recover".

If I take the cover off (horizontal case, not tower), the machine will
boot and run fine with no problem. But the instant I replace the
cover, before the cover is even fully on, the system hangs as before.
This has happened several times, there is no way that it is a
coincidence.

Have tried reseating all the cards and memory, formatting HDD and
reinstalling, scanning for hard disk errors. The processor is old
enough not to need a fan so thats not an issue.

Any ideas at all would be most appreciated. Thanks a million
-Colm

 

[Alien Zord]

Hi

I have a bizarre problem with an old (but still useful) Dell Optiplex
which I've been given. It's a 166MHz with 128MB RAM.

If I boot (Win NT), after something between 2 and 25 minutes the
machine will hang and wont boot up again at all until I switch it off
and give it maybe half an hour to "recover".

If I take the cover off (horizontal case, not tower), the machine will
boot and run fine with no problem. But the instant I replace the
cover, before the cover is even fully on, the system hangs as before.
This has happened several times, there is no way that it is a
coincidence.

Have tried reseating all the cards and memory, formatting HDD and
reinstalling, scanning for hard disk errors. The processor is old
enough not to need a fan so thats not an issue.

Any ideas at all would be most appreciated. Thanks a million
-Colm

PSU fan not spinning any more?

 

[SpongeBob]

PSU fan not spinning any more?

Sounds like the cover (case) is shorting on something...pinching/touching a
wire, cable, etc...

 

[DaveW]

It sounds like a thermal overheating issue. With the cover off, and the
additional cooling from being open, it doesn't hang.

 

[~misfit~]

PSU fan not spinning any more?

I think the two salient points here are:

A, It's a Dell

B, He said "But the instant I replace the cover, before the cover is even
fully on"

Some proprietry machines, including Dell, if memory serves, may have a
"Chassis Intrusion detection switch". I think this *may* be the problem.
Sometimes thay can be disabled from the BIOS, or maybe just checking if it
has such a switch and either taping it down or disconnecting it.

I could be wrong, but that's my first thought. Switch malfunction.

And, to the OP, does that machine have a bloody great big Dell heatsink that
sits in the airflow intake for the PSU? If it does (that's what they had
originally) you're right, it doesn't need a CPU fan as long as the PSU fan
is still going strong. If however the CPU heatsink has been replaced then it
*will* benefit from a fan. The Dell P1 HS I have here has two spring-steel
'leaves' attached to it (for want of a better word) that seem to have been
designed to contact the PSU and the case-lid. (I don't know if that's
relevant or not). It's also a big thing, about as big as a coffee cup
(although a different shape of course).

 

[Alien Zord]

I think the two salient points here are:

A, It's a Dell

B, He said "But the instant I replace the cover, before the cover is even
fully on"

1) I noticed it and chose to disregard it because you and I can take 5
seconds to put a cover on but a complete layman can take minutes especially
on a Dell some of which can be really awkward. With the cover off the
machine might be running at a temp just bellow which a component causes
electrical latch-up. Put the cover on and the temp will rise rapidly
bringing on the fault.

2) If the OP boots the machine from cold with the cover on it will run for 2
to 20 mins ruling out a cover switch.

3) The fact that the machine will boot again after being off for half an
hour suggests its a thermal issue and due to its age PSU fan failure is
quite a possibility.

 

[~misfit~]

1) I noticed it and chose to disregard it because you and I can take 5
seconds to put a cover on but a complete layman can take minutes
especially on a Dell some of which can be really awkward. With the
cover off the machine might be running at a temp just bellow which a
component causes electrical latch-up. Put the cover on and the temp
will rise rapidly bringing on the fault.

2) If the OP boots the machine from cold with the cover on it will
run for 2 to 20 mins ruling out a cover switch.

3) The fact that the machine will boot again after being off for half
an hour suggests its a thermal issue and due to its age PSU fan
failure is quite a possibility.

Yep, all good points. I was just throwing something else into the mix. That
bit about the thing failing before he's got the cover on properly just made
me think about those switches.

You're right, I'd look at the PSU fan first. I just thought that was a bit
obvious. I do have a tendancy to think that certain procedure has been
followed before asking for help. Bad habit of mine.

 

[SpongeBob]

It sounds like a thermal overheating issue. With the cover off, and the
additional cooling from being open, it doesn't hang.

Then why would it hang "the instant" he puts the cover back on...Case Short
Circuiting...IMHO.

 

[Trent©]

Hi

I have a bizarre problem with an old (but still useful) Dell Optiplex
which I've been given. It's a 166MHz with 128MB RAM.

You could have many possible problems...or a combination of problems.
I'd start by getting a HSF for that CPU. They had a lot of heat
problems with the 166.

If I boot (Win NT),

What version? Get the latest upgrades.

after something between 2 and 25 minutes the
machine will hang and wont boot up again at all until I switch it off
and give it maybe half an hour to "recover".

It doesn't sound like a heat problem...but ya never know. It looks
like too great a time range for it to be heat related. Are you doing
the same task(s) on or about the time the machine freezes...playing a
song?...using the mouse?...etc. Are you running any Norton stuff?

If I take the cover off (horizontal case, not tower), the machine will
boot and run fine with no problem.

Are you sitting anything on top of the case?... the monitor maybe?

But the instant I replace the
cover, before the cover is even fully on, the system hangs as before.
This has happened several times, there is no way that it is a
coincidence.

Then describe 'instant I replace the cover'. What stage of 'replace'
are you at when it freezes?

Have tried reseating all the cards and memory, formatting HDD and
reinstalling, scanning for hard disk errors. The processor is old
enough not to need a fan so thats not an issue.

It was an issue. I think it was AMD that had the most problems.

Good luck...let us know.


Have a nice week...

Trent

Follow Joan Rivers' example --- get pre-embalmed!

 

[Trent©]

B, He said "But the instant I replace the cover, before the cover is even
fully on"

Some proprietry machines, including Dell, if memory serves, may have a
"Chassis Intrusion detection switch". I think this *may* be the problem.
Sometimes thay can be disabled from the BIOS, or maybe just checking if it
has such a switch and either taping it down or disconnecting it.

I could be wrong, but that's my first thought. Switch malfunction.

I built a LOT of 166's. I never saw a mainboard back then that had
that feature! lol


Have a nice week...

Trent

Follow Joan Rivers' example --- get pre-embalmed!

 

[Colm Ward]

Hi

Thanks a lot for all your very helpful replies.

The PSU fan is spinning although the PSU unit in general is well
dusty.

Its not a wire getting pinched by the cover as there is nothing in the
slots for the case except some metal clips which I presume are for the
case lid to make conductive contact with the base chassis.

Also I couldnt find anything resembling a switch around the edges and
there is no mention of intrusion detection in the BIOS.

It takes me about 10 seconds to put the cover back on. The machine can
hang anytime from when I start to lower the case onto the base
chassis, to the last push to click it into place.

My own feelings were that it was a thermal issue, well either that or
it had to be some kind of electromagnetic thing as the machine seemed
to 'sense' the approach of the cover sometimes.

So I'm wondering if I should replace the PSU, or maybe install another
fan somewhere. I did try putting a spare fan beside the processor at
one point, I think the machine stayed running for slightly longer but
it still froze up in the end (the cover was on at that point).

What would be the best place to install an extra fan - beside the
processor or beside the memory? The processor does have a big green
heat sink but it does not make contact with the case lid. It's
situated at the opposite corner of the chassis from the PSU so I don't
know if you could say that it is in the airflow of the PSU fan.

Also should a fan blow or suck air over the thing it's supposed to
cool? Does direction of airflow matter?

thanks again
-Colm

 

[SpongeBob]

Hi

Thanks a lot for all your very helpful replies.

The PSU fan is spinning although the PSU unit in general is well
dusty.

Its not a wire getting pinched by the cover as there is nothing in the
slots for the case except some metal clips which I presume are for the
case lid to make conductive contact with the base chassis.

Also I couldnt find anything resembling a switch around the edges and
there is no mention of intrusion detection in the BIOS.

It takes me about 10 seconds to put the cover back on. The machine can
hang anytime from when I start to lower the case onto the base
chassis, to the last push to click it into place.

My own feelings were that it was a thermal issue, well either that or
it had to be some kind of electromagnetic thing as the machine seemed
to 'sense' the approach of the cover sometimes.

So I'm wondering if I should replace the PSU, or maybe install another
fan somewhere. I did try putting a spare fan beside the processor at
one point, I think the machine stayed running for slightly longer but
it still froze up in the end (the cover was on at that point).

What would be the best place to install an extra fan - beside the
processor or beside the memory? The processor does have a big green
heat sink but it does not make contact with the case lid. It's
situated at the opposite corner of the chassis from the PSU so I don't
know if you could say that it is in the airflow of the PSU fan.

Also should a fan blow or suck air over the thing it's supposed to
cool? Does direction of airflow matter?

thanks again
-Colm





"DaveW" <[email protected]> wrote in message

Well...without getting really small and climbing into the unit
itself...while you put the cover on...I can't be positive, but your symptoms
are that of shorting out. I don't think any component in there would go from
ambient temperatures to overheating in less than 10 seconds...Unless you
used a blow torch of course. Often when closing those bulky covers, things
shift slightly...especially if they are not tight. Slight movement of the
motherboard could cause it to short off the case or some adjacent component
touching it. Loose standoff's could create a "shorting" issue...or possibly
a screw that has fallen between the motherboard and case...Anyway these
"instant lockups" due to physical movement of parts are almost always due to
something touching what it shouldn't. My 4 cents now I guess...

 

[kony]

I built a LOT of 166's. I never saw a mainboard back then that had
that feature! lol

I know an Asus 'TX board did, probably some of the Intel boards that Dell
"likely" used did too, but for the most part none of the OEM P1 systems
I've seen had the actual switch, feature utilized.

 

[kony]

Hi

Thanks a lot for all your very helpful replies.

The PSU fan is spinning although the PSU unit in general is well
dusty.

Why? Regular system maintenance.
Even if you deem the machine not worthy of a thorough cleaning it's
relatively quick/easy to take a paint brush and (with the system unplugged
from AC) brush away the dust buildup from the power supply intake and
exhaust, fan, as well as the case intake area.

Its not a wire getting pinched by the cover as there is nothing in the
slots for the case except some metal clips which I presume are for the
case lid to make conductive contact with the base chassis.

It'd make contact regardless, usually those are present to prevent
rattles.

Also I couldnt find anything resembling a switch around the edges and
there is no mention of intrusion detection in the BIOS.

Check the motherboard, the wires leading away from the pin headers.
Chassis intrustion pin header is "usually" separate from the other (front
panel) header(s) but on a Dell they often tried to integrate all pins into
a dual-row pin header so follow the wires away from the board.

It takes me about 10 seconds to put the cover back on. The machine can
hang anytime from when I start to lower the case onto the base
chassis, to the last push to click it into place.

My own feelings were that it was a thermal issue, well either that or
it had to be some kind of electromagnetic thing as the machine seemed
to 'sense' the approach of the cover sometimes.

Like some nudists, it wants to feel free of it's clothes?
It's not an electromagnetic problem.
It should not be a heat issue with it crashing THAT soon after attempt to
install the cover unless it's just a very unlikely situation where the CPU
was literally always within a degree of instability.

So I'm wondering if I should replace the PSU, or maybe install another
fan somewhere. I did try putting a spare fan beside the processor at
one point, I think the machine stayed running for slightly longer but
it still froze up in the end (the cover was on at that point).

It could be a lot of things with a system that age. Try removing the
memory, cleaning the contacts, reinstalling. Same goes for other cards.
If the machine is really worth the time then get some electroinc cleaning
spray (non-residue type) and spray into every area making an electrical
contact on the board... on an old dirty system that will probably make it
look REALLY nasty inside, afterwards, due to the dirt pooling wherever the
cleaner puddled before drying, but this is probalby the "last leg" of
service for that machine, the asthetics of the interor are not important
compared to a time and cost effective determination of viability for
future use, considering it's age/reliability and (lack of) performance.

What would be the best place to install an extra fan - beside the
processor or beside the memory?

The memory does not need a fan.
If you want to put a fan on the CPU and have a spare, do so... I mean, a
normal heatsink fan replacement, not a rigged fan, there is no point in
reusing the Dell heatsink if you're going to put a fan in there anyway.



The processor does have a big green

heat sink but it does not make contact with the case lid. It's
situated at the opposite corner of the chassis from the PSU so I don't
know if you could say that it is in the airflow of the PSU fan.

I think I've seen one of those Dells, but was a long time ago. There
should be a highly perforated front chassis panel where the incoming air
moved past the CPU 'sink, and "maybe" a mount on that front chassis wall
for a 60mm fan, if there wasn't a fan there already, originally.

Also should a fan blow or suck air over the thing it's supposed to
cool? Does direction of airflow matter?

Blowing will result in more airflow through the sink tines but mostly
you'd want to preserve the original chassis airflow, from front to back
towards the power supply. If it was designed to operate without the fan
it should still continue to do so... the CPU isn't suddenly creating more
heat... maybe if you can get those mounting clips off without damaging it
you might clean off the 'sink bottom and apply fresh thin coat of thermal
compound.

I don't think it's the CPU heat though, in 10 seconds it's not going to be
getting that much hotter. The other reason is that with the cover on,
there should/would be MORE airflow past the 'sink because now the power
supply's fan is moving air through the system much, much more effectively.

 

[~misfit~]

I built a LOT of 166's. I never saw a mainboard back then that had
that feature! lol

Understandable. I did mention the fact I was talking about 'proprietary'
machines. A lot of which are designed for use by corporations. I've seen
IBM, Dell and Compaq P1's (and later) amongst others that had 'chassis
intrusion detection' switches, presumably so the admin can tell if the user
has been inside the machine. They were all controlled by BIOS, which, in the
above instance, one would think would be password-protected by the admin.
When the feature is activated a splash-screen comes up briefly on boot up
saying "Warning: Case has been opened" or similar and can't be cleared
without going into the BIOS. I was thinking that, maybe, this machine has
the switch but the function is turned off in BIOS but may still be causing
trouble.

(I used to buy a lot of ex-corporate machines at auction)

LOL indeed, please read the post before commenting. I've built a LOT of
166's as well, I'm not talking about home-builds. Do you understand
'proprietary'?

 

[~misfit~]

Why? Regular system maintenance.
Even if you deem the machine not worthy of a thorough cleaning it's
relatively quick/easy to take a paint brush and (with the system
unplugged from AC) brush away the dust buildup from the power supply
intake and exhaust, fan, as well as the case intake area.


It'd make contact regardless, usually those are present to prevent
rattles.


Check the motherboard, the wires leading away from the pin headers.
Chassis intrustion pin header is "usually" separate from the other
(front panel) header(s) but on a Dell they often tried to integrate
all pins into a dual-row pin header so follow the wires away from the
board.


Like some nudists, it wants to feel free of it's clothes?
It's not an electromagnetic problem.
It should not be a heat issue with it crashing THAT soon after
attempt to install the cover unless it's just a very unlikely
situation where the CPU was literally always within a degree of
instability.



It could be a lot of things with a system that age. Try removing the
memory, cleaning the contacts, reinstalling. Same goes for other
cards. If the machine is really worth the time then get some
electroinc cleaning spray (non-residue type) and spray into every
area making an electrical contact on the board... on an old dirty
system that will probably make it look REALLY nasty inside,
afterwards, due to the dirt pooling wherever the cleaner puddled
before drying, but this is probalby the "last leg" of service for
that machine, the asthetics of the interor are not important compared
to a time and cost effective determination of viability for future
use, considering it's age/reliability and (lack of) performance.


The memory does not need a fan.
If you want to put a fan on the CPU and have a spare, do so... I
mean, a normal heatsink fan replacement, not a rigged fan, there is
no point in reusing the Dell heatsink if you're going to put a fan in
there anyway.



The processor does have a big green

I think I've seen one of those Dells, but was a long time ago. There
should be a highly perforated front chassis panel where the incoming
air moved past the CPU 'sink, and "maybe" a mount on that front
chassis wall for a 60mm fan, if there wasn't a fan there already,
originally.




Blowing will result in more airflow through the sink tines but mostly
you'd want to preserve the original chassis airflow, from front to
back towards the power supply. If it was designed to operate without
the fan it should still continue to do so... the CPU isn't suddenly
creating more heat... maybe if you can get those mounting clips off
without damaging it you might clean off the 'sink bottom and apply
fresh thin coat of thermal compound.

I don't think it's the CPU heat though, in 10 seconds it's not going
to be getting that much hotter. The other reason is that with the
cover on, there should/would be MORE airflow past the 'sink because
now the power supply's fan is moving air through the system much,
much more effectively.

All good suggestions as usual Dave. If I remember correctly some of those
old Dells were a bit of a bitch to get the cover back on,, resulting in some
flexing of the case sometimes. *Although* Colm says that sometimes if he
even approaches the case with the cover it freaks. Checking mobo screws for
tightness wouldn't hurt I guess. Also, and this may sound silly, sometimes
with machines like that it's easy to touch the power button when putting the
cover on, they tend to protrude through the cover or have a push button that
contacts the power switch proper.

I dunno, just suggesting things as they pop into my head. It's hard to
trouble-shoot hardware without the machine in front of you.

I certainly agree about cleaning out the PSU of dust though, essential
maintainence with any machine.

 

[Trent©]

Thanks a lot for all your very helpful replies.
Welcome.


The PSU fan is spinning although the PSU unit in general is well
dusty.

If you decide to clean it, use a vacuum cleaner. Don't use a brush. A
brush will simply dislodge the dust particles and let them drop into
the PSU housing. Use a vacuum to pull out the dust.

Its not a wire getting pinched by the cover as there is nothing in the
slots for the case except some metal clips which I presume are for the
case lid to make conductive contact with the base chassis.

Those clips are simply used to align the cover...although they do
serve an ancillary purpose of grounding.

Also I couldnt find anything resembling a switch around the edges and
there is no mention of intrusion detection in the BIOS.

That's because it wasn't even invented until much later.

It takes me about 10 seconds to put the cover back on. The machine can
hang anytime from when I start to lower the case onto the base
chassis, to the last push to click it into place.

If it happens EVERY time, I'd certainly suspect something
electrical...as SpongeBob eluded to. It could also be a hard drive
problem...but that kind of freezing with the hard drive is usually
because of interruption of power and/or signal.

Next time it happens putting on the case, immediately take the case
off again. See if you can feel the hard drive spinning.

My own feelings were that it was a thermal issue, well either that or
it had to be some kind of electromagnetic thing as the machine seemed
to 'sense' the approach of the cover sometimes.

As Bob said, it's probably not heat related. It wouldn't happen every
time you put the cover on. And you said that it happened anywhere
from 2 minutes to 20 minutes. A heat problem would generally be more
specific in timing.

So I'm wondering if I should replace the PSU, or maybe install another
fan somewhere. I did try putting a spare fan beside the processor at
one point, I think the machine stayed running for slightly longer but
it still froze up in the end (the cover was on at that point).

You might have a problem that's beyond your scope. If you know
computers, I'd take out the mainboard and then reinstall it...checking
for proper installation and any shorting problem. Next, I'd check
power and signal to the hard drive.

What would be the best place to install an extra fan - beside the
processor or beside the memory? The processor does have a big green
heat sink but it does not make contact with the case lid. It's
situated at the opposite corner of the chassis from the PSU so I don't
know if you could say that it is in the airflow of the PSU fan.

Take the heat sink off...install a heat sink and fan combo. Is it an
AMD CPU?

Good luck.


Have a nice week...

Trent

Follow Joan Rivers' example --- get pre-embalmed!

 

[Noozer]

If you decide to clean it, use a vacuum cleaner. Don't use a brush. A

brush will simply dislodge the dust particles and let them drop into
the PSU housing. Use a vacuum to pull out the dust.

WRONG!!! Use a can of compressed air. Do *NOT* put a vacuum cleaner near
your PC unless it was designed to vacuum computer components (not a cheapy
flashlight sized vacuum you buy for $3.99 either)

Those clips are simply used to align the cover...although they do
serve an ancillary purpose of grounding.

Some cases have small tabs that protrude specifically for grounding... Of
course they're usually painted over so I doubt they do little good. They're
usually long (1"?) and skinny with a small bumb on the end.

That's because it wasn't even invented until much later.

I've got a 486 with one of them switches, so it's possible. Not likely
though.

If it happens EVERY time, I'd certainly suspect something
electrical...as SpongeBob eluded to. It could also be a hard drive
problem...but that kind of freezing with the hard drive is usually
because of interruption of power and/or signal.

I'd suspect a loose wire/connector or a static problem. The reason it runs
so long when the cover is already on is that you aren't hovering over it
poking at it so it takes longer to knock the loose component or zap the
chassis.

First I'd try wiggling wires/cables while the PC was running to make sure
nothing was loose. Next I might try flexing the case and mainboard to look
for shorts. After that I'd probably disassemble the system, blow it out and
reassemble, putting cards in different slots than before, etc.

I don't have the original post, but I think the CPU here was a P166... many
didn't have fans. If the CPU is close to the bottom front of the case I'd
add a case fan to the chassis at this point (modern cases are built for
this, not sure about yours)

Considering the prices of low end PC's (What can you find at Walmart for
example) it may be simpler and better in the long run to replace the PC.

 

[kony]

WRONG!!! Use a can of compressed air. Do *NOT* put a vacuum cleaner near
your PC unless it was designed to vacuum computer components (not a cheapy
flashlight sized vacuum you buy for $3.99 either)

I still like my paintbrush suggestion, but that was only a quick-n-dirty
attempt at improving airflow towards the end of keeping CPU cooler for
troubleshooting period... for optimal cleaning of a sysystem this age,
allowed to get that dirty, the power supply needs opened and cleaned
inside too.

 

[Trent©]

WRONG!!! Use a can of compressed air. Do *NOT* put a vacuum cleaner near
your PC unless it was designed to vacuum computer components (not a cheapy
flashlight sized vacuum you buy for $3.99 either)

WRONG!!! Compressed air will make it worse than simply dusting...in
most cases.

Been using a vacuum cleaner for over 12 years...MANY times.

Never a problem.

And PLEEEZZZEEEE don't tell me about static electricity! lol


Have a nice week...

Trent

Follow Joan Rivers' example --- get pre-embalmed!