Adcom GFA-7700 - Manual (Page 6)

6
12VDC Triggering (4a)
The GFA-7700 is a very high power amplifier and as such must be directly connected to the wall outlet
or an appropriate surge protector or AC line conditioner. It must never be connected to the “switched”
outlets on the rear panel of a pre-amplifier. Usually this would mean that when you turn on/off
your pre-amplifier you would have to turn on/off your power amplifier separately. We have however
provided the ability to control the OFF/ON function of the GFA-7700 by a 12Volt DC output jack on the
rear of certain ADCOM pre-amplifiers and tuner pre-amplifiers. When using this feature the front panel
Power Switch must be left in the in “on” position. To connect you will need a monaural mini phone plug
to monaural mini phone plug cable of appropriate length (not included) to reach from the rear panel of
the amplifier to the rear panel of the pre-amplifier. Contact your dealer for information on using this
feature with ADCOM and other brand pre-amplifiers. Although 12VDC is optimal, the circuit will operate
from approx. 5 to 30VDC. Center conductor (tip) is positive (+).
AC Fuse (4b)
The AC Fuse protects the electronic circuits of the GFA-7700. Normally, this fuse
will fail only if there is an overload within the GFA-7700. It may, however, fail if the
amplifier attempts to deliver very high power into very low-impedance loudspeakers.
In either case, BE SURE TO REPLACE THE AC Fuse ONLY WITH AN EXACT REPLACEMENT
FUSE. The proper fuse values are:
Fuse Rating BUSS ® Littlefuse ®
For 115 volt operation ....... 15 Amp 250 Volt .......... AGC-5/250V.................. (3AG) 312005/250V
For 230 volt operation ....... 8 Amp 250 Volt ............ AGC-3/250V.................. (3AG) 312003/250V
WARNING
Before attempting to replace a failed fuse, be certain to unplug the AC Power Cord from the AC wall
outlet to prevent possible electrical shock. Replace the AC Fuse only with one identical in type and
rating as printed on the rear panel. DO NOT USE ANY SUBSTITUTE FUSES WITH DIFFERENT RATINGS OR
VALUES. Failure to observe this precaution may cause serious damage to the amplifier circuits, MAY
CREATE A FIRE HAZARD, AND MAY VOID THE WARRANTY.
If the Power LED (7) does not glow, it may be an indication that the AC fuse has blown. If you are using
the 12VDC Triggering feature (above) it may be possible that there is a problem with that connection.
To determine if the problem is caused by a malfunction in the 12VDC system, remove the small plug
inserted into the 12VDC Triggering jack. Press the front panel power switch to turn off the amp, and
immediately re-press the power switch. If the problem is caused by the 12VDC triggering circuit the
amp will turn on and the LED will glow. DO NOT attempt repair of the 12VDC system. If you are not
sure, or the amplifier displays other symptoms, please consult the RESOLVING PROBLEMS section on
page 13. To remove the fuse-holder cap, you will need a 1⁄4” standard flat-blade screwdriver. Place the
screwdriver in the recessed slot in the cap. Turn the cap 1/8-turn counter-clockwise, until the cap pops
out towards you. Grasp the cap with your fingers and pull it completely out. The fuse is inserted in the
back of the cap; gently pull it free.
Since the fuse has a ceramic body, 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.
AC Power Cord (5)
The AC cord provides power to operate all the GFA-7700’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-7700.