Adcom GTP-602 manual Troubleshooting, Servicing

Troubleshooting Tip

Your GTP-602’s circuitry is built around advanced microprocessors. The GTP-602 may exhibit occasional anomalies arising from AC line surges, etc. If you experience unexpected behavior, or if the GTP-602 “locks up” and does not respond to control input, reset it by turning the rear panel power switch off. (Do not use the remote control’s “power” button). Wait 10 seconds and then turn the GTP-602 on using the rear panel power switch.

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.

14 ADCOM GTP-602 Owner’s Manual