Service Information - Adcom GTP-860II Owner's Manual

Troubleshooting
Use the troubleshooting notes above to solve common
situations that don't require professional attention. If the
steps stated in possible solution do not resolve your prob-
lem, then please contact your ADCOM dealer or call the
ADCOM customer service department. Any problems not
covered here should be brought to the attention of your
ADCOM dealer or ADCOM customer service department.
A special note on "hum:" When there is a low-volume
"hum" audible throughout your speakers, even with the
main volume turned all the way down, you have a com-
mon phenomenon known as a "ground loop." A ground loop
is basically a difference in ground voltages between two
or more components which are connected electrically and
which creates multiple current paths where there must only
be one. This difference in potentials creates a 60Hz low-
level sound (approximately a low A), that seems to "hum."
It can be caused by adding new components to your system,
but that does not imply there is anything electrically wrong
with any new component. With the advent of audio/video
and home theater systems, the problem has become com-
monplace. Generally, the cause is the Cable-TV incoming
signal line. This new incoming line may add an additional
ground at a different potential to the AC line ground of
your other equipment (refer to note I and 2, to trouble-
shoot a hum problem).
Note 1: Cable TV systems can sometimes contribute to
ground loop problems which cause "hum." To determine
if your cable system is the contributing factor, disconnect
the Cable-TV incoming signal line (round, 75Ω) at the wall,
Troubleshooting Tip
Your GTP-860II's circuitry is built around advanced microprocessors. The GTP-860II may exhibit
occasional anomalies arising from AC line surges, etc. If you experience unexpected behavior, or
if the GTP-860II "locks up" and does not respond to control input, reset it by turning the front
power switch off. (Do not use the remote control's "power" button.) Wait 10 seconds and then
turn the GTP-860II
This unit is manufactured under license from Dolby Laboratories Licensing Corporation. It is additionally licensed
under one or more of the following patents: U.S. number 3,959,950, Canadian numbers 1,004,603 and 1,037,877.
Dolby® Pro Logic®, and Dolby Digital® are registered trademarks of Dolby Laboratories Licensing Corporation.
Manufactured under license from Digital Theater Systems, Inc. US Patent Number 5,451,942 and other world-
wide patents issued and pending. "DTS," "dts," "DTS Digital Surround," are trademarks of Digital Theater
Systems, Inc. Copyright 1996 Digital Theater Systems, Inc. All Rights Reserve
| ADCOM GTP-860 II Owner's Manual
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or the first component the cable is connected to (i.e. the
cable box, or VCR). If the hum is no longer present, you
must insert a "75Ω ground loop isolator" before reconnect-
ing the line. You should check with your ADCOM dealer to
obtain one. If the "75Ω ground loop isolator" works only
partially or not at all, then please read note 2 to complete
the troubleshooting procedure.
Note 2: Make sure that the power amplifier is at least 6"
from processor or other equipment using microprocessors.
Usually putting another component between them is suf-
ficient to minimize the hum. If this does not reduce the
hum, turn the system off and disconnect all Inputs from
the amplifier. If the hum still persists, then your dealer or
service center must examine the unit/system. If the hum
disappears, try another set of RCA cables. Connect one RCA
cable at a time to see if one specific cable is responsible.
If any or all cables cause the hum to appear, then the unit
should be evaluated for proper operation by your dealer or
authorized service center. Please see our website or call us
for a list of authorized service centers in your area.
Servicing
ADCOM has a technical service department to answer
questions pertinent to the installation and operation of your
unit. In the event of difficulty, please contact us for prompt
advice. If your problem cannot be resolved through our
combined efforts, we may refer you to an authorized repair
agency, or authorize return of the unit to our factory. To aid
us in directing you to a convenient service center, it would
be helpful if you indicate which major city is accessible to
your home.