Adcom THX GFA-7000 - Manual (Page 13)

TROUBLESHOOTING
RESOLVING PROBLEMS
Use the chart below to solve common situations that don’t require professional attention. If
the steps stated in POSSIBLE SOLUTION do not resolve your problem, 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 common
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”, hence the name.
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 commonplace. 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 Note1 and 2 below to
troubleshoot a hum problem).
SYMPTOM POSSIBLE REASON POSSIBLE SOLUTION
Power LED does not
glow No sound
AC Power Cord(O) not plugged in. Plug in AC Power Cord(O).
AC Fuse(O) blown. Replace AC Fuse(O).
Transformer thermal protection engaged Wait until unit cools down, it will reset.
Power LED glows,
but no sound
Preamp or source unit is not on Make sure whole system is on.
Connections in rear of amp are loose. Verify all connections on rear of amp
One channel not
producing sound
INPUT(O) orOUTPUT(O) connector
disconnected or loose.
Verify both connections on that channel
Speaker disconnected. Verify connection at speaker.
Internal protection engaged Bring to Dealer or Service Center
Hum from all speakers
at any volume
Ground loop (difference in ground voltages
between components).
If Cable TV is present (see Note 1)
If Cable TV is not present (see Note 2)
Hum from all speakers
(hum goes up or
down with volume)
Problem with source unit (CD, tape, etc.),
or RCA cable connecting that source unit
to the preamp.
Try different source (tuner, tape, etc)
and/or different RCA cable
Hum from the amplifier
Itself
Some major appliance, dimmer, halogen or
fluorescent light is creating interference
Make sure all appliances, dimmers and
suspect lights are off
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, 75Q) 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 "750. Ground Loop Isolator” before reconnecting the line. You should check with your Adcom Dealer to
obtain one. If the “75Q 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 the Preamp and/or Processor. Usually putting another
component between them is sufficient 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 amplifier. 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 preamp or processor should be
evaluated for proper operation by your Dealer or Authorized Service Center.
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