"fac 51" said:
hello all im using the asus p4p800e-deluxe with a 3g pentium 4 processor and
300 w power supply since november then yesterday came back to my pc and the
screen was blank went to reboot and have been getting the system failed cpu
test ever since . checked the cpu no sign of burning or damage the board
seems to be ok it wasn't running at a high temprature got me old mother
board back in and there's no virus . i just dont no what to do next apart
from take it in to check if the board and cpu are ok ? any help would be
appreciated
In a situation like this, the power supply is the most likely
part to have failed. If you have a digital multimeter, set it
on volts, connect the black lead to a nut on the I/O area of
the back of the computer (so if the black lead falls off, it
cannot come in contact with anything else). Using the red lead,
grab a spare disk drive power cable, and probe the +12V and +5V
pins, while the computer is running. The +3.3V will be harder
to check, because it is on the main 20 pin cable. (Some older
ATX power supplies have a 6 pin AUX power connector, and it
has +3.3V on it, for use with your meter). The voltages should
be within 5% of their normal values. For example, if the +12V
is lower than +11.4, try another power supply.
http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf (pg.29)
If you don't own a multimeter, then find a spare supply somewhere
and swap it in.
If the power supply is just weak and not completely dead, you
can do a cardboard test. Remove the motherboard from the computer
case and place it on top of a piece of cardboard on your work
table. Remove the power supply from the case. Strip all the
components off the motherboard, being careful to store them in
antistatic bags.
Plug amplified speakers into the Lineout on the back of the
computer, so you can listen to the voice post messages.
With just the motherboard and PSU, and no other LEDs or switches
in place, plug in the power supply. Momentarily touch a
screwdriver tip, to the two pins on the PANEL header intended
for the power switch. The power supply fan should start to
spin, and the voice post message should complain about no CPU.
Plug in the CPU and repeat the test. This time it will complain
there is no RAM in place, and that means the CPU was able to
execute some instructions. Keep adding components like memory,
video card, keyboard, mouse and so on. At some point, either
it will not give the voice post message you expect (like saying
the RAM is bad, after you plugged in the RAM), or if the power
supply is bad, it might not POST at all. Using voice post and
the cardboard test, you may be able to isolate the faulty
component.
When adding or removing components from the motherboard, you
should never do that while +5VSB is present on the board. That
is the reason the green warning LED is on the motherboard surface.
While switching off the power supply, via the switch on the back
of the computer, should cause the LED to go off, a conservative
practice is to unplug the computer before going inside it. Failure
to take proper regard for +5VSB, can cause things like memory
DIMMs to fail, if the wrong pin makes contact with a "hot" socket.
The +5VSB powers components on the computer, when the computer is
in standby (S3 suspend to ram). Unplugging the computer is also
required, if doing the "clear CMOS" thing.
Paul
