Atlantic Technology A-2000 Manuale di istruzioni - Pagina 9

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Instruction Manual

Potential Ground Loops in a Complex A/V System

Suggestion 1 To determine if a cable TV connection is responsible for the
hum, first turn all components off. Disconnect the cable TV feed to your
systematthefirstplacewhereitconnectstoyourcomponents.Alternatively,
disconnect the cable TV wire (not theAC wire to the cable box,but the cable
antennawire)whereitisconnectedatthewalloutlet.Turnyoursystemback
on,and listen if the hum has disappeared.If removing the cable TV feed has
eliminated the hum, you will need to insert a Ground Loop Isolator before
reconnecting the cable TV feed, or contact your cable TV operator to see
if they can better isolate your cable feed. Ground Loop Isolators should be
available from your local AudioVideo dealer.
Suggestion 2 Turn off all components in your system,and then disconnect
the input cables at the amplifier. Turn the amplifier back on, and see if the
humisstillpresent.If thehumdisappears,thefaultmaybeintheinputcables
used. Try replacing them with cables that have better shielding, and make
certain that the input cables are not running on top of or directly adjacent
to and parallel with anyAC power cords.Change the cables one at a time to
determine if one, or all cables is responsible. If the hum disappears when
the input cables are disconnected,but returns after the cables are changed
andthesystemre-connected,theproblemmaybecausedbyyourprocessor,
receiver or preamplifier.
Suggestion3 Groundloopproblemsmayalsobecausedbypoorgrounding
of the electrical system in your home,particularly when there are multiple
components with three prong grounded power cords.Try unplugging these
componentsoneatatime,andseeif oneorallof themiscausingtheproblem.
Theultimatesolutiontothistypeof problemistore-wireyourhousewithan
Ground Loop Diagram
Cable Feed
60Hz AC
Ground
Coax Cable
A/V Cables
Main House
Grounding
isolated,star type grounding configuration.We recognize,however,that this
may be impractical and expensive.In some cases,the use of an approvedAC
Power Isolation Transformer of sufficient capacity may solve this problem.
Warning: If you suspect that the grounding system in your home's
electrical wiring is causing the hum problem, it is important that you do
not make any changes to the wiring yourself. Only a licensed electrician
should make any changes to household wiring, and they must be made
in full compliance with all local building, safety and electrical codes.
Suggestion 4 Hum may also be caused by faulty earth grounds in your
home's electrical system. In the past, cold water pipes were often used for
the earth ground,so it is important to make sure that your ground connec-
tion is still valid and has not become loose or corroded.The cold water pipe
method may no longer be valid in some locations due to requirements that
the water meter be isolated from the water mains with a length of PVC pipe,
thus interrupting the ground circuit.The safest,and most reliable,approach
may be to provide your own ground.This can be accomplished by having a
licensedelectriciandriveatleastfivefeetof copper-jacketedsteelgrounding
rod into the earth,and using that for your grounding connection.
Suggestion5 If youhavehuminyourvideodisplaydevice(barsthatrollup
throughimageat12-14secondintervals),thismayberelatedtohumyoualso
experienceinyouraudiosystem.Theprevioussuggestiontipsmayhelpwith
this also.If not,try isolating the ground in the projectors video signal cable
with a base-band video isolation transformer,such as the JensenVB-1BB.
If the hum persists after all of the above suggestions have been tried,contact
our customer service department for assistance.
AC Line
AC Ground
A Few Words About Hum and Noise
60Hz AC
Ground
AC Line
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