Adcom GFP-715 owner manual Servicing, Troubleshooting

8 ADCOM GFP-715 Owner’s Manual

	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 amplifier	Some major appliance, dimmer, halogen or		Make sure all appliances, dimmers and
	itself	fluorescent light is creating interference.		suspect lights are off.
Troubleshooting			or the first component the cable is connected to (i.e. the
			cable box, or VCR). If the hum is no longer present, you
Use the troubleshooting notes above to solve common			must insert a “75Ω ground loop isolator” before reconnect-
situations that don’t require professional attention. If the			ing the line. You should check with your ADCOM dealer to
steps stated in possible solution do not resolve your prob-			obtain one. If the “75Ω ground loop isolator” works only
lem, then please contact your ADCOM dealer or call the			partially or not at all, then please read note 2 to complete
ADCOM customer service department. Any problems not			the troubleshooting procedure.
covered here should be brought to the attention of your			Note 2: Make sure that the power amplifier is at least 6”
ADCOM dealer or ADCOM customer service department.
			from processor or other equipment using microprocessors.
A special note on “hum:” When there is a low-volume			Usually putting another component between them is suf-
“hum” audible throughout your speakers, even with the			ficient to minimize the hum. If this does not reduce the
main volume turned all the way down, you have a com-			hum, turn the system off and disconnect all Inputs from
mon phenomenon known as a “ground loop.” A ground loop			the amplifier. If the hum still persists, then your dealer or
is basically a difference in ground voltages between two			service center must examine the unit/system. If the hum
or more components which are connected electrically and			disappears, try another set of RCA cables. Connect one RCA
which creates multiple current paths where there must only			cable at a time to see if one specific cable is responsible.
be one. This difference in potentials creates a 60Hz low-			If any or all cables cause the hum to appear, then the unit
level sound (approximately a low A), that seems to “hum.”			should be evaluated for proper operation by your dealer or
It can be caused by adding new components to your system,			authorized service center. Please see our website or call us
			for a list of authorized service centers in your area.
but that does not imply there is anything electrically wrong
with any new component. With the advent of audio/video			Servicing
and home theater systems, the problem has become com-
monplace. Generally, the cause is the Cable-TV incoming			ADCOM has	a technical service department to answer
signal line. This new incoming line may add an additional
			questions pertinent to the installation and operation of your
ground at a different potential to the AC line ground of
			unit. In the event of difficulty, please contact us for prompt
your other equipment (refer to note I and 2, to trouble-
			advice. If your problem cannot be resolved through our
shoot a hum problem).
			combined efforts, we may refer you to an authorized repair
Note 1: Cable TV systems can sometimes contribute to			agency, or authorize return of the unit to our factory. To aid
ground loop problems which cause “hum.” To determine			us in directing you to a convenient service center, it would
if your cable system is the contributing factor, disconnect			be helpful if you indicate which major city is accessible to
the Cable-TV incoming signal line (round, 75Ω) at the wall,			your home.