Building a PC is not rocket science, but
there are still many potential pitfalls. Ian Jackson looks at ten common
mishaps you should aim to avoid!
Motherboard shorting on the case
A computer motherboard can be
turned on by shorting the power switch pins
An inevitable part of any PC build is
mounting your shiny new motherboard into the case. Most cases hold the board in
place via brass standoffs that you screw into the motherboard tray. Since there
are several different form factors of motherboard, there are usually far more
mounting holes than you will actually need. A common mistake made by first time
PC builders is to screw in all of the brass standoffs, regardless of
whether they marry up with a hole on motherboard. The trouble with doing this
is that you have a piece of sharp, conductive metal coming into contact with
the board where it shouldn’t. This can damage the delicate traces on the
underside of your board, or at the very least will stop it from posting due to
a short. To avoid this scenario, simply check which holes in the motherboard
tray marry up with those on your motherboard before screwing them in.
Underspecified PSU
A lot of really cheap PC cases come bundled
with PSUs that have a surprisingly high rating. These appear to be bargain –
after all, why spend upwards of $60 on a branded 500W power supply when you can
buy a $30 case and get one of the same capacity thrown in? This is a classic
case of there being no such thing as a free lunch. These bundled power supplies
are invariably quoting, at best, their peak operational voltage, or more often
than not, are simply lying about the wattage they are capable of delivering. A
cheap bundled PSU will probably power an entry-level system with integrated
visuals capably enough, but if you have system with a powerful quad-core
processor and a discrete video card, it’s not going to cut the mustard. Very
few of these power supplies are actually capable of delivering any more than
about 200W sustained and do so in a horribly inefficient manner. We mentioned
in our buyer’s guide the value of having an 80 Plus certified PSU. Some of the
cheap PSUs bundled with cases fail to achieve even 50% efficiency! This means
that if your system has a requirement of 100W to tick over, the PSU will be
pulling 200W from the wall and wasting this energy in the AC-to-DC conversion
process.
An overstressed PSU can be a rather
alarming thing. If your power supply makes a twittering noise or starts to
smell bad when the system is at load, this normally means the capacitors,
transformers and voltage regulator modules within the PSU are running beyond
their specified maximum. At this point your PSU is on borrowed time.
High-quality PSUs have protective circuits that cut off power to the system should
operational limits be exceeded, and they have surge protection built in so that
if the worst happens and the PSU blows, you don’t lose any of your hardware.
Unfortunately, with cheap bundled PSUs there are no such guarantees; if a
component within your cheap PSU blows, there’s a very good chance your precious
motherboard, video card and hard drives could get cooked along with it.
Should a PSU within your system blow,
immediately unplug it from the mains. Leave the system where it is it for a few
minutes to cool down, and then while making sure you are well grounded, remove
the PSU and send it back for warranty exchange. Never try to open up a PSU and
DIY repairs, as this can be dangerous. PSUs are inherently non-user serviceable
and their capacitors can hold a sizable amount of power even when disconnected
from the mains – certainly enough to give you a nasty jolt.
Wrongly mounted cooler
Modern CPU coolers are certainly a lot more
forgiving than they were a decade ago, but it’s still possible to mount them
incorrectly, especially if you have a complicated third-party heatsink with
support for multiple socket types. This is often a mistake made by experienced
system builders as well as novices, as over confidence might make you think
you’re too goo to be bothered with reading instruction manuals. When tasked
with a cooler you are not familiar with, always read the installation
instructions, as some of the brackets and mounting arms need to be installed in
quite a counter-intuitive manner. Mount the arms at the wrong point of the
cooler’s base, for example, and your cooler could easily be hovering a few
millimetres above the surface of the chip rather than making proper contact.
Modern processors have built-in thermal
cut-offs that prevent an incorrectly mounted cooler from permanently damaging
the computer. This wasn’t always the case, however – I myself have fried a
number of first-generation AMD Athlon chips by thinking the cooler was properly
attached when it wasn’t. if you’re repairing an older computer, you should
therefore take particular notice of this common mistake!
