Adcom GFA-7605 - Manual (Page 10)

10
Since the fuse has a ceramic body and you cannot visually
examine the fuse element it is therefore suggested that
you replace it with an identical substitute or bring the fuse
to your ADCOM dealer so they may check its integrity. To
replace the fuse, insert it in the back of the fuse-holder
cap. Place the cap into the fuse-holder. Place the
screwdriver in the recessed slot, gently press in and turn
1/8-turn clockwise.
(5) AC Power Cord
The AC cord provides power to operate all the GFA-
7605/7607’s circuits. Its plug can be connected to a
standard wall outlet provided the outlet supplies a voltage
compatible with the power requirements printed on the
rear panel of the GFA-7605/7607.
DESCRIPTION OF UNIT : FRONT PANEL
(6) On/Off Switch
The On/Off Switch controls power to the power
transformer and circuits of the GFA-7605/7607. Whenever
the GFA-7605/7607 is energized the Power LED (7)
will glow. To turn the GFA-7605/7607 on, press the
push-button. It will remain in the “engaged” position while
the unit is energized. To turn the GFA-7605/7607 off, press
the push-button in and release and it will move to the
“disengaged” position.
(7) Power LED
This LED will glow whenever the On/Off Switch (6) is
turned on and the GFA-7605/7607 is energized. The Power
LED indicates that there is AC voltage being fed to the
amplifier, but it does not signify that all the amplifier’s
circuits are in operation. If, for example, one of the
Thermal Protection LEDs (9) glows, that amplifier channel
will not produce sound even though the Power LED may
still glow. When the GFA-7605/7607 is turned off, the
Power LED will take some time to fade out completely. It
may take up to 30 seconds to fully extinguish.
Additionally, the internal power transformer is provided
with a thermostat which will interrupt power into the
transformer if its temperature exceeds 125°C. This high
temperature will seldom, if ever, be encountered unless
the amplifier is subjected to abnormal conditions, such
as operation into loads of less than 3 ohms at very high
listening levels, etc. If the AC Fuse (4) has not failed, the
Power LED is out, and the Thermal Protection LED (9) does
not glow, this would indicate that the thermostat within
the transformer has opened.
Once the temperature within the transformer decreases
to a normal level, the thermostat will reset itself
automatically and normal operation will resume. If you
are to avoid tripping the thermostat in the transformer
continually, you must reduce the sound level demands,
correct the load impedance of the loudspeakers, or both.
(8) Thermal Protection LEDs
The GFA-7605/7607 are provided with a thermal protection
circuit which will shut down the individual amplifiers
if its heatsink temperature reaches 85°C. The Thermal
Protection LEDs will light whenever the thermal protection
circuit in its respective channel has been triggered and the
amplifier is inoperative. The thermal protection circuitry
will typically be triggered by very high power demands
into impedances much lower than the amplifier is capable
of driving at those levels. If any amplifier channel’s
output through the loudspeaker(s) ceases abruptly, and
its Thermal Protection LED glows, you will know that its
heatsink temperature has become unacceptably high
and the circuitry is protecting the amplification devices.
Please note that the Power LED (7) will remain on and the
amplifier will still be energized. Once the temperature
of the heatsink(s) drops to a safe operating level, that
amplifier will automatically resume operation.
Activation of the Thermal Protection circuitry in any
of the amplifiers in the GFA-7605/7607 is an indication
that the amplifier has been over-driven or that the
load the loudspeakers are presenting to the amplifier
is unreasonably low. If you wish to prevent recurrent
activation of the thermal protection circuitry, you must
reduce the volume-level demands or correct the load
impedance condition which may be causing activation of
this circuitry.
(9) Distortion Alert LEDs
The Distortion Alert circuit is a unique ADCOM distortion
detection system which reads all forms of non-linear
distortion such as THD, IM, slew-induced, “clipping,” etc.
The Distortion Alert LEDs will light when distortion reaches
approximately 1% regardless of impedance, voltage/