(^182) PC Hardware: A Beginner’s Guide
clean the outside air is may have an effect on the PC, but it won’t have any impact on the
hard disk at all.
While the HDA is sealed, it is not airtight (or watertight, for that matter). This doesn’t
mean that outside air can get in and gum u pthe works, though. The HDA has a vent that
allows it to equalize the air pressure through a breather filter. This vent and filter adjust
forbarometricpressurechangesthatthePCmayexperience—betweenitsmanufacturing
plant in Taiwan at near sea level and an office in Denver one mile above sea level, for
example.Asthealtitudechanges,airissuckedinorventedoutthroughthebreatherfilter
until the internal air pressure equals the outside air pressure. Most manufacturers rate an
altitude range for their hard drive’s operation, typically between 1,000 feet below sea
level and around 10,000 feet above sea level. This covers nearly all scuba divers and
mountain climbers. The problem of operating the disk drive outside of its altitude range
is that there may not be enough air pressure to float the heads.
While not directly related to the air filters, there is one other environmental consider-
ation for hard disks—adapting to temperature changes. When the ambient operating
temperature of a PC changes significantly, the hard disk must be allowed time to accli-
mate itself before it is powered on. For example, if a hard disk is shipped during the winter
and sits for some time at temperatures less than 50 degrees Fahrenheit, it should be allowed
to acclimate to normal room temperatures for at least 13–15 hours before it is powered
up. Check with your hard disk’s manufacturer for information on its environmental and
operating condition requirements.
Logic Boards
Hard disk drives include logic boards that control the functions of the drive’s spindle and
head actuator and interact with the device controller to pass data to and from the disk.
Some disk drives also include the hard disk controller on the drive. Along with the spindle
motor, logic boards account for a large share of disk drive failures. In fact, many disk failures
are really logic board failures and not problems with the mechanical parts of the disk.
The logic board of a disk drive can be easily replaced, but most people tend to replace
the entire drive. The logic board is usually mounted to the disk drive through a plug
connectorandoneortwoscrews.Replacingthelogicboardisalsoaneasywaytotrouble-
shoot a drive you suspect of logic rather than mechanical problems.Connectors and Jumpers
Figure 9-7 shows two of the three general types of connectors found on most disk systems:
data and power. The third type, an optional connector on most drives, is not shown; it is
usually a tab with a single screw hole used to connect the disk drive to the chassis for
grounding purposes. Your disk drive’s documentation should have information on
whether your drive offers or requires the grounding connection.
Thedata connector, which is also called aninterface connector,carries both the data and
command signals from the controller and CPU to and from the disk drive. Some drives use