Adcom GTP-740 - Manual (Page 44)

5.0 TROUBLE SHOOTING
Your GTP-740’s circuitry is built around advanced microprocessors. The GTP-740
may exhibit occasional anomalies arising from AC line surges, etc. If you experience
unexpected behavior, or if the GTP-740 “locks up” and does not respond to control
input, reset it by turning front power switch off. (Do not use the remote control’s
“power” button.) Wait 10 seconds and then turn the GTP-740 on. This will reset the
internal control circuitry and solve almost all problems.
SYMPTOM
Power LED does not light
Power LED glows
but no sound
POSSIBLE REASON
AC Power Cord not plugged in
AC Fuse failed
Power amp or source unit is not on
Ball Switch (rear panel) is on
No sound from one channel Connections in rear of amp are loose
Input or Output connector
disconnected or loose
POSSIBLE SOLUTION
Plug in AC Power Cord
Replace AC Fuse
Make sure whole system is on
Put Ball System switch in Off position
Verify all connections on rear of amp
Verify both connections on that channel
Hum from all speakers
(any volume)
Hum from all speakers
(increases or decreases with
change in system volume)
Speaker disconnected
Ground loop present
(difference in ground voltages
between components)
A major appliance, dimmer,
halogen or fluorescent light may be
creating interfereruie
Problem with source unit (CD, etc.)
Problem wiffi cable connecting that
source to the Tuner/pre-amp
Verify connection at speaker
If cable TV is present, see Note 1
If cable TV is not present, see Note 2
Make sure all appliances, dimmers and
suspect lights are off
Try different source to verify
Try different cable to verify
Note 1; Cable TV systems can contribute to ground loop problems which, in turn, cause “hum.” To determine whether your cable system is
the contributing factor, disconnect the cable TV incoming signal line (the round, 75 ohm cable) before it first connects to your system. If the
hum disappears, you should insert a ”75 ohm Ground Loop Isotator” between the cable down Jead and your system. Check with your
ACCOM Dealer to obtain one. If the isolator does not fully cancel the hum, please read Note 2 to complete the troubleshooting procedure.
Note 2; Make sure that the power amplifier is at least 6" from ttie Tuner/Pre-amp. Usually, putting another component between these two
units is sufficient to minimize the hum. If this does not work, turn the system off and disconnect all input cables from the amplifier. Turn the
system on again. If the hum persists, your Dealer or Service Center should dteck the amplifier. If the hum disappears, try another set of
RCA cables. (Remember to turn your entire system off whenever you change cables. You may also need to wait a few moments after
turning the amplifier off until the power supply discharges to avoid nasty “thumps" when you disconnect or connect cables.) Connect one
RCA cable at a time to see if the hum returns and. if it does, which specific cable is responsible. Replace that cable. If the hum persists with
any (or all) cables, then your GTP-740 should be checked by your Dealer or Authorized Service Center
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