Chapter 14: Power Supply and Electrical Issues^329
Noise The amount of sound measured in decibels (dB), such as electrical
buzz and fan noise, that the power supply and its fan produce.
Mean time before failure The manufacturer’s best estimate of how long
it should be before the power supply should fail or develop problems.
Safety certifications It is important to know what safety testing and
certifications the power supply has been awarded. Some companies and
buildings have strict requirements on the electrical equipment that can
be purchased and operated on its premises. Included in the power supply’s
specifications should be a list of test and certification agencies that have tested
and approved it. These certifications indicate which safety, environmental, and
regulatory requirements the power supply has been tested against and passed,
including design, RF and EMI emissions, environment issues, and product safety.
The most common of these certifications are UL (Underwriters’ Laboratory), CSA
(CSA International), TUV (Technischer Uberwachungs-Verein), and FCC
(Federal Communications Commission).Electrical Power Issues
A PC’s power supply is the source and cause of more component failures than any other
component of the PC. It is the cause of at least a third of PC failures, and many other prob-
lems that show up in other components are actually caused or aggravated by the power
supply. A faulty power supply can burn out or weaken the electrically fragile electronics
on the motherboard and peripheral devices.
The power supply is like the guardian at the gate for the PC when it comes to its power.
AC power tends to be a fluctuating, noisy, and unreliable power source, and the power
supply has the job of smoothing out the problems in the AC line to produce steady, reliable
DC power. Some of the more common electrical problems encountered by the power
supply are as follows: Spikes AC power fluctuates within a range of from 90 to 130V. Nearly all
power supplies are built to handle AC fluctuations within this range. However,
there are occasional unexpectedly high voltage fluctuations that last only a
short period time that can pose problems for PC power supplies and any other
electrical equipment. An electrical spike is caused by such things as lightning,
switching from one generator to another, or even electrical motors on the same
power source as the PC.
Blackouts A blackout is just what it sounds like: a total loss of the AC power
source. Blackouts can last only a split second or several days. If you have no
other power source, then your hope is that the Hold Up Time on your power
supply is longer than the blackout. Typically, the Hold Up Time is about 1/20th
of a second, and if the blackout lasts any longer than that, most likely your PC
will reboot or shutdown.