Troubleshooting Tip
Your GTP-860’s circuitry is built around advanced microprocessors. The GTP-860 may exhibit
occasional anomalies arising from AC line surges, etc. If you experience unexpected behavior,
or if the GTP-860 “locks up” and does not respond to control input, reset it by turning the front
power switch off. (Do not use the remote control’s “power” button.) Wait 10 seconds and then
turn the GTP-860 on. This will reset the internal control circuitry and solve most problems.
RESOLVING PROBLEMS
Use the chart on the opposite page 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.
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 cre-
ates 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.”
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 I and 2, to troubleshoot
a hum problem).
Note 1:
Cable TV systems can sometimes contribute to ground loop problems which cause “hum.” To determine if your
cable system is the contributing factor, disconnect the Cable-TV incoming signal line (round, 75Ω) at the wall, or the first
component the cable is connected to (i.e. the cable box, or VCR). If the hum is no longer present, you must insert a “75Ω
Ground Loop Isolator” before reconnecting the line. You should check with your ADCOM Dealer to obtain one. If the “75Ω
Ground Loop Isolator” works only partially or not at all, then please read Note 2 to complete the troubleshooting proce-
dure.
Note 2:
Make sure that the power amplifier is at least 6” from the Preamp and/or Processor. Usually putting another
component between them is sufficient to minimize the hum. If this does not reduce the hum, turn the system off and
disconnect all Inputs from the amplifier. If the hum still persists, then your Dealer or Service Center must examine the
amplifier. If the hum disappears, try another set of RCA cables. Connect one RCA cable at a time to see if one specific
cable is responsible. If any or all cables cause the hum to appear, then the preamp or processor should be evaluated for
proper operation by your Dealer or Authorized Service Center.
32 | ADCOM GTP-860 OWNER’S MANUAL