On the right side it looks like it could be burned. I don't see too
many CPUs because they are always covered with the fan.
It looks darker than dust to me. I hope I am wrong.
But I replaced the power supply and the problem remained. That rules
out the PS.
I left out some details. The computer only stayed on for a few min
and then shut it self down.
Since it was a spare machine I took out the hard drive and reformatted
it. I had also removed the mobo because the original thought was to
turn it into a gaming machine for my nephew for Christmas, but he has
another gift in mind over a computer. I was going to just take an old
small spare hard drive and reinstall Windows XP. When I started
assembling it again, I remembered the loud popping sound my nephew
said it made and I decided to just order the same type mobo. That is
when I pulled the fan off and saw what looked like it could have been
smoke.
Something caused a pop and caused the computer to shut down. My
trouble shooting skills are pretty low. Replacing parts is about as
good as I can do. I really thought it was between the mobo and the
PS. I replaced one thing thinking it would be either it or the other.
Now It can be the CPU.
I may still do the Windows install if the CPU just looks like normal
dust to you.
I did notice in the instructions that it does have a " PC Health
Monitoring" feature.
I don't know much about what that could tell, but I wish I had noticed
that before I took everything apart.
PC Health is the BIOS hardware monitor. The SuperI/O chip (takes care
of floppy interface, serial ports, parallel port, low speed stuff), it
also has interfaces on it for measuring a few temperatures and voltages.
The CPU temperature is the one you'd be interested in. The CPU temperature
will be displayed in that BIOS screen. It gets updated perhaps once
a second.
You'd switch on the computer, enter the BIOS, go to the PC Health page
in the BIOS, and view the CPU temperature readout. See if the temperature
is gradually rising, until it gets too high and the computer shuts off.
It might get up to around 100C or so, before it's "lights out".
The CPU will have a THERMTRIP signal, which turns off the computer
if the CPU gets too hot. Reasons for the CPU to get too hot are:
1) VCore voltage is incorrect. A defect in the VCore regulator circuit
could do it. Or, on an enthusiast board, setting a "boost" for VCore
too high could do it. On one of the Tomshardware projects, they force
the CPU to draw 200 watts, and stuff gets pretty warm. I don't think
that's the case here. But if something I can't see in the picture,
part of VCore has blown, then that might result in the CPU overheating.
Normally, the CPU would be destroyed by that much of an overvoltage.
2) Heatsink retention levers were loose, and the heatsink
isn't touching the CPU. The thermal paste pattern on the top of
your CPU isn't ideal right now, so when you reassemble the machine,
you can clean off the paste and use fresh thermal paste. You want to
make sure the heatsink is really pressing against the CPU. I've had
one computer, where it was overheating, because the heatsink was
binding on some adjacent metal. It helps to inspect the heatsink from
all four sides, to decide whether it's sitting flat or not.
3) CPU fan stops spinning. The CPU fan speed will be listed in the
PC Health screen as well. Some designs, run the fan at low RPM
(like 300-500 RPM or so). But most of the stuff I have here, is
likely 1800 RPM or higher. Don't forget to plug in the CPU fan
cable, before switching on.
If (2), the thing can turn off in a couple seconds.
If (3), it might take a while for the CPU to heat up the metal
in the heatsink. But without the fan spinning, it may eventually
get so hot, as to trigger THERMTRIP and turn off the PSU.
I tried to look for things that are "burst" in your photo. There are
a few components underneath the retention frame, that I can't see too well.
If an electrolytic actually explodes, the material released looks like
vaporous trails of "soot" floating in the air. So much of it is released,
you'd think it was a black confetti storm. It's pretty gross and messy.
When you take electrical engineering, there's usually at least one
individual who has to see what that looks like, and the rest of us
get to inhale the results :-(
Your "dust" doesn't look exactly the right color, but it's
pretty hard to judge at this distance.
It's also possible, the CPU fan pulled in polluted air, from
some other thing in the machine that popped. Like, a component
on an adjacent video card, or the CPU fan could also have pulled
smoke from the PSU, into the fan blades.
I've spent as long as two hours with a jewelers loupe, or with
a binocular low-power microscope, inspecting printed circuit
boards for defects. For really microscopic faults, that's how
long it takes (try finding a crack in an 0603, when there are
a thousand of them). You have to twist them at an angle sometimes,
to see details off to the side of a component. You can't possibly
hope to capture all the available information with one or two
camera shots. It really takes a pair of eyes right on the scene
to catch every little detail.
I think your VCore may have a few tantalum caps in the area, and
I don't know what color those are when they blow. I've had an
epoxy-dipped tantalum blow in my living room as a kid, and it
bounced off the living room wall like a bullet. There's no place
for gas pressure to go on those. The epoxy makes an air-tight
enclosure around the "sugar cube" of stuff inside. I think it
fractures near the base, and the gas pressure is released. And
of the ones I've had fail, that was the most spectacular.
But your sound was a "pop", and that's either arcing, or
it's an electrolytic (like the rubber bung in the bottom
of the cap, causing the cap to lean like the Leaning Tower
of Pisa). Continue your inspection, and see if some
electrolytic (cylinder) outside of camera range in the
photo, has blown. Pressure is either release on top,
via the stamped pattern in the aluminum shell. Or, the
rubber bung in the bottom of the capacitor, is ejected
from the bottom, and the capacitor leans at an angle
from the vertical.
Not every component failure in a PC, causes it to
stop running. People have bumped SMT components on
motherboards, causing them to detach and fly off, and
the computer continues to run. So not every component
on there, is in the critical path. You might have to lose
just about all the bulk bypass caps, before the computer
would crash for example. And there might be half a dozen
or more of those.
If a cap blows on a VCore circuit, it's relatively easy
to fix. It's when a user ignores something like that, and
"lets it burn for a while", that one of those toroidal
coils or one of the MOSFETs with the three legs on it,
gets burned. And those are harder to find substitutes for.
When a cap fails, it can stress adjacent components that
are part of the same circuit leg, and when those other
components fail, it makes the thing harder to fix.
Paul
If this was a rush job