Loran said:
Yea this computer have been on three monitors
There are few diagnostic features on computers, but there is one you can
take advantage of. That is the computer case speaker. The computer case
speaker can deliver a "beep" code, based on defective hardware that
has been detected.
The very first test, when you are getting no response, is whether pushing
the power button on the front, makes the fans spin. That tells you that
the power supply is not completely fried. It doesn't tell you, though,
if all voltages are present on the supply. The supply has outputs for
-12V, 3.3V, 5V, 5VSB, +12V, for example. The fans are connected to +12V,
so hearing fans spinning, tells you that voltage is present. And +12V also runs
the Vcore power converter, which in turn, runs the processor.
If you are getting that far, then you can try one of the "strip down
tests". Unplug the computer. Remove the side cover. Remove the RAM, taking
careful note of the orientation for when you put it back later. Store the
RAM in an antistatic bag, the same kind used to hold new PCI or AGP
cards.
Now, plug in and turn on the machine. Do you hear a beep pattern for "bad RAM" ?
On some computers, it might be a beep, a slightly long delay, and then
that pattern repeated over and over again.
The beeping is important. The speaker beeps, under CPU control, so if you
hear the beep, then you know the CPU is working, it was able to read a
little bit of BIOS code, the power supply likely has working voltages and
so on. So any beeping, is a good sign.
If you don't hear a beep, when the RAM is missing, then something is
preventing the CPU from running. Since power supply failures are quite
common, you might suspect a problem with the power supply at this point.
A motherboard problem would be the next most likely problem (do a visual
check for bad capacitors). The following picture shows some bad capacitors
on a motherboard. Millions of bad capacitors were shipped in past years,
leading to premature motherboard failure. Some computer companies, actual
have warranty extensions available, and will replace a motherboard with
bad capacitors, well past the original warranty. And they do that, because
of the known problem with batches of bad caps.
http://www.badcaps.net/images/caps/kt7/image004.png
In addition to removing the RAM, you can also remove the video card. The
BIOS probably checks for bad RAM first, then checks for the presence of
a video card. Once you hear the "bad RAM" beep pattern, you can put the
RAM back (with the computer unplugged), and try the same test, only with
the video card missing. If the computer has built-in video, then it will
likely always have access to some video output, so it may be harder to
make it beep a "missing video" beep pattern. Occasionally, a computer
will be "struck dumb" by a bad video card, and removing the card (with
the computer unplugged), may be enough to get a response from the CPU
and beep speaker. (Once the bad video card is removed, the CPU works
well enough to beep the speaker.)
So those are a few things to try.
There is no reason to buy new hardware, until you've tried a few
things first. For example, if you were still not getting any beeps,
then a multimeter purchased at the hardware store, and set to the
volts range, could be used to probe the main power supply
connector, and check for -12V, 3.3V, 5V, 12V DC and so on. But
that requires some knowledge of electricity and how to make
measurements, so not everyone enjoys doing that. If you need power
supply reference documents, there are a series of them, here. The
connector wire colors and voltages, are shown in the later pages
of these documents. (Non-standard Dell supplies, would not correspond
to these standards, but most new computers do.)
http://web.archive.org/web/20030424...org/developer/specs/atx/ATX_ATX12V_PS_1_1.pdf
http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf
http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf
Paul
