Hardware Reference
In-Depth Information
You replace because of the economics of the situation with computer hardware. The bot-
tom line is that financially it is much cheaper to replace a failed circuit board with a new
one than to repair it. For example, you can purchase a new, state-of-the-art motherboard
for around $100, but repairing an existing board normally costs much more than that.
Modern boards use surface-mounted chips that have pin spacing measured in hundredths
of an inch, requiring sophisticated and expensive equipment to attach and solder the chip.
Evenifyoucouldfigureoutwhichchiphadfailedandhadtheequipmenttoreplaceit,the
chipsthemselvesareusuallysoldinquantitiesofthousandsandobsoletechipsareusually
not available. The net effect of all of this is that the replaceable components in your PC
havebecomedisposabletechnology.Evenacomponentaslargeandcomprehensiveasthe
motherboard is replaced rather than repaired.
Troubleshooting by Replacing Parts
You can troubleshoot a PC in several ways, but in the end it often comes down to simply
reinstalling or replacing parts. That is why I normally use a simple “known-good spare”
technique that requires very little in the way of special tools or sophisticated diagnostics.
In its simplest form, say you have two identical PCs sitting side by side. One of them
has a hardware problem; in this example let's say one of the memory modules are defect-
ive. Depending on how and where the defect lies, this could manifest itself in symptoms
ranging from a completely dead system to one that boots up normally but crashes when
running Windows or software applications. You observe that the system on the left has
the problem but the system on the right works perfectly—they are otherwise identical.
The simplest technique for finding the problem would be to swap parts from one system
to another, one at a time, retesting after each swap. At the point when the DIMMs were
swapped, upon powering up and testing (in this case testing is nothing more than allow-
ing the system to boot up and run some of the installed applications), the problem has
now moved from one system to the other. Knowing that the last item swapped over was
the DIMM, you have just identified the source of the problem! This did not require an
expensive DIMM test machine or any diagnostics software. Because components such as
DIMMs are not economical to repair, replacing the defective DIMM would be the final
solution.
Although this is very simplistic, it is often the quickest and easiest way to identify a prob-
lem component as opposed to specifically testing each item with diagnostics. Instead of
having an identical system standing by to borrow parts from, most technicians have an
inventory of what they call “known-good” spare parts. These are parts that have been pre-
viously used, are known to be functional, and can be used to replace a suspicious part in
a problem machine. However, this is different from new replacement parts because, when
you open a box containing a new component, you really can't be 100% sure that it works.
