Adcom GFA7807 owner manual Symptom Possible Reason Possible Solution

RESOLVING PROBLEMS

Use the chart below 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.

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.

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 creates 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 procedure.

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.

12