Star Tech Journal

November 1992
STAR* TECH Joumal
.~
Hook this to the screw on the
outlet cover plate and while you
are at it, check to see if the outlet
plate is at ground potential. This
can be done with a polarity and
ground checker that is discussed
below.
Locations almost always have
other equipment plugged into the
same circuit. This can cause the
voltage available to your machine
to be dropped below tolerable lev-
els when their equipment is
turned on.
Simply plug the tester into the
adapter after the pigtail is
hooked up to the see if everything
is normal. If the tester shows the
polarity is reversed then turn the
adapter over. If it shows a bad
ground, you may have to get an
electrician to re-wire the outlet
with a newer style three wire re-
ceptacle.
Also, devices with large motors or
neon lights can cause surges or
high noise levels in the circuit.
Maintaining a good ground is not
only advantageous for the rea-
sons above but it will also help
~eep your equipment from gener-
~ ating interference to TV's and
radios that are local to your
equipment. This doesn't just
mean the interference can bother
your location, it can bother people
several doors down!
The bottom line is that you are
responsible for any interference
your equipment generates and
you must fix it if someone has a
complaint about it. Read the FCC
warning on the back of your
equipment!
VOLTAGE LEVEL AND INTEGRITY
The voltage available to your
machine(s) should be at the
proper level, not too high and not
too low. It should be within plus
or minus five percent. This
roughly comes out to 111 to 125
~olts. Most machines will toler-
~te voltages a little above and
below these figures but keep in
mind that you do not always have
the circuit to yourself.
outlet. The best way to do this
would be under load.
Simply plug in the piece of equip-
ment you want to use on the cir-
cuit and pull the plug out about
an eighth of an inch. Put your
multimeter on the AC scale at a
setting that will allow measure-
ment of at least 150 volts and
read the value from hot to neu-
tral. These are the two straight
blades (the round one is the
ground). Be extremely careful:
Don't short any of the three prongs
together with your probe!
You should get a reading within
tolerable levels at this point. If
you do not, you or the location
may need to hire an electrician to
find out the reason.
This can cause plenty of problems
especially to equipment with
logic boards.
MAKE A FEW CHECKS
To check out your electric supply
will take very little time and ef-
fort and it will avoid service calls
for those "ghost" problems.
• First, check the polarity of the
outlet. Many electrical and elec-
tronic supply stores have small
and inexpensive testers that will
get the job done. They will tell you
whether the circuit is ok or if one
or more of the outlets terminals
are incorrectly wired. This type of
tester is available for under $20.
• The other tester that you will
need is probably in your toolbox
already. A multimeter will allow
you to read the voltage at the
This will differ from state to state
and town to town. It all depends
on the laws in your area. In some
places you may be allowed to
make your own repairs. Do not
attempt your own repairs unless
it is legal and you are quite sure
you know what you are doing!
If you feel that your equipment is
exposed to alot of noise on the
line, you can try a computer grade
line filter to get rid of it. A good
line filter can cost a few bucks but
it may be needed. It also works
the other way around, it will re-
duce the amount of noise your
equipment will put into the cir-
cuit. This can also reduce the in-
terference that your equipment
generates to TV's and radios
nearby.
LOADS
Always keep track of how much
current your machine is drawing
from the circuit. Most circuits are