| ADCOM GFP-715 Owner’s Manual8
9ADCOM GFP-715 Owner’s Manual |
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,
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.
ServicingADCOM 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.
SYMPTOM POSSIBLE REASON POSSIBLE SOLUTION
Power LED does not AC Power Cord(s) not plugged in. Plug in AC Power Cord(s).
glow. No sound AC Fuse(s) failed. Replace AC Fuse(s).
Transformer thermal protection engaged. Wait until unit cools down. It will reset.
I2V DC triggering malfunctioning. Reset power switch manually. Check
connection of 12V DC trigger at source.
Power LED glows, Preamp or source unit is not on. Make sure whole system is on.
but no sound Connections in rear of amp are loose. Verify all connections on rear of amp.
One channel not INPUT(s) or OUTPUT(s) connector Verify both connections on that channel.
producing sound disconnected or loose.
Speaker disconnected. Verify connection at speaker.
Internal protection engaged. Bring to Dealer or Service Center.
Hum from all speakers Ground loop (difference in ground voltages If Cable TV is present (see Note 1).
at any volume between components). If Cable TV is not present (see Note 2).
Hum from all speakers Problem with source unit (CD, tape, etc.), Try different source (tuner, tape, etc.)
(hum goes up or or RCA cable connecting that source unit and/or different RCA cable.
down with volume) to the preamp.
Hum from the amplier Some major appliance, dimmer, halogen or Make sure all appliances, dimmers and
itself uorescent light is creating interference. suspect lights are off.