Adcom GFA-7400 User Manual

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.
SYMPTOM |
| POSSIBLE REASON \
| POSSIBLE SOLUTION
Power LED does not
AC Power Cord(O) not plugged in.
Plug in AC Power Cord(0)
glow. No sound
AC Fuse(0)failed.
Replace AC Fuse(O).
Transformer thermal protection engaged
Wait until unit cools down, it will reset.
12VDC triggering malfunctioning
(GFA-7400 Only)
Reset power switch manually Check
connection of 12VDC 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
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.
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 Note 1 and 2 on next page, to
troubleshoot a hum problem).
14

Adcom GFA-7400 Specifications

Power

continuous power per channel into 8 ohms	100 watts
continuous power per channel into 4 ohms	150 watts
power consumption quiescent	96 VA
maximum power consumption	1440 VA
power consumption at 100 watts into 8 ohms	1165 VA
power supply voltage	115 VAC - 50/60 Hz

Distortion

IM distortion SMPTE at 8 ohms	≤ 0.075%
IM distortion SMPTE at 4 ohms	≤ 0.075%
IM distortion CCIF at 8 ohms	≤ 0.025%
IM distortion CCIF at 4 ohms	≤ 0.025%
THD + noise at 100 watts into 8 ohms at 20Hz	0.0012%
THD + noise at 100 watts into 8 ohms at 1kHz	0.0012%
THD + noise at 100 watts into 8 ohms at 10kHz	0.02%
THD + noise at 100 watts into 8 ohms at 20kHz	0.025%
THD + noise at 150 watts into 4 ohms at 20Hz	0.025%
THD + noise at 150 watts into 4 ohms at 1kHz	0.025%
THD + noise at 150 watts into 4 ohms at 10kHz	0.035%
THD + noise at 150 watts into 4 ohms at 20kHz	0.045%

Performance

frequency response at 1 watt into 8 ohms	+0, -0.25 dB
power bandwidth	1.5 Hz to 65 kHz
dynamic headroom into 4 ohms	2.5 dB
signal to noise ratio	≥ 110 dB
gain	29 dB
input sensitivity for 1 watt	0.1 volts
input sensitivity for 100 watts	1.0 volts
input impedance	50 kΩ
damping factor	≥ 400
rise time	4.5 µS

Weight and Dimensions

chassis dimensions	5” (127mm) x 17” (432mm) x 14” (355.6mm)
maximum dimensions	5 3/4” (146mm) x 17” (432mm) x 15” (381mm)
weight	42 lb. (19.1 kg)
packed weight	48 lb. (22.8 kg)