JC said:
Ok I have a problem starting up a computer. I think it may be the
memory but I am not sure. It will start up but with no picture. I
changed to another monitor that I know works with a new video card that
I know works. The same thing happens. The computer will start up but
nothing is visable on the monitor. I don't have another stick of memory
to test it with to confirm it is the memory. Any ideas of what it could
be? Any help would be appreciated.
JC
I would recommend some "beep" tests. The computer case speaker should
be connected to the PANEL header while you do the tests. If the
video card is missing or if the memory stick is missing when the
computer is started, the computer should beep the speaker. The
beep is generated, by the CPU reading some BIOS code, and
the CPU programs a chip to make the beep sound. If removing the
video card and the memory stick produces no beep from the computer
speaker, then we are down to CPU, motherboard, power supply.
(No beep, means the CPU cannot be running the BIOS code.)
Disconnect the disk drive cables, before you run those tests.
Make note of where, and how the cables were connected. The
reason for disconnecting the drives, is in case they are shorting
something. Once the drive cables are disconnected from the
motherboard, carry out your beep tests.
If the CPU, motherboard, power supply combo won't beep, then
one of the three is broken or something is not connected right.
Some motherboards use a ATX12V 2x2 power connector, and that
must be in place for the CPU to run the BIOS code and POST.
If you have a multimeter, set it to the volts range, and
measure the voltages on the ATX main power connector. You
should be able to probe a bit of exposed metal on the back
side of the main power connector, where the wires go into
the nylon shell. See if +3.3, +5, +12, -5V, -12V, +5VSB
are all present and accounted for. If your meter has an
alligator clip for the probes, clip the black lead to a
screw on one of the I/O connectors, so it doesn't get
shorted to something.
The most frequent failure in the computer, will be the supply.
Disk drives are probably next. Memory after that. CPU and
motherboard should be pretty reliable. The one exception to
that rule, is the millions of motherboard that got bad
capacitors a couple years back. Many Abit motherboards
died with swelling or leaking capacitors around the CPU
socket. Other motherboard brands were affected as well, and
even major computer supplies got hit. Depending on the
age of the computer, I would look for the tall cylinders
with the plastic sleeve on the outside, and see if the
tops are bulging (they should be flat), or if there is
a brown fluid near the base of the capacitor (dries to
a brown stain). If you have bad capacitors, then the
motherboard needs to be repaired or replaced. Considering
the price of motherboards, repair doesn't make too much
sense, unless you know how to solder, and know where to
buy the correct kind of capacitors.
As for cleaning the contacts on electronic components,
that is way down my list of things to try. If you
visually examine a connector, and the contacts are
shiny, and there is no obvious goo on them, leave the
contacts alone. The gold plating is thin, and won't
last long if you attack it with an eraser. If you
suspect a contact problem, it is just as easy, to insert
and remove the component a few times, to scrape a
fresh contact. That way, no new materials (eraser
shavings) are added to the equation. Organic solvents
are also a double edged sword, as they can leave traces
of impurities on the contacts. Even touching your
fingers to the contacts is a bad idea, as your fingers
leave deposits of oils and salt on the contacts. The
best treatment for a connector, is no treatment at all.
HTH,
Paul
