Adcom GFA7707, 7705 manual Troubleshooting, Resolving Problems

Troubleshooting

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.

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 likely have a common phenomenon known as “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 potential creates a 60 Hz low-level sound (approximately a low A#), that appears 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 from the AC line ground of your other equipment.

Symptom

Power LED does not glow No sound

Power LED glows, but no sound

One channel not producing sound and/or

Thermal LED Blinking

Hum from all speakers at any volume

Hum from all speakers (hum goes up or down with volume)

Hum from the amplifier itself

Possible Reason

AC Power Cord (4 ) not plugged in AC Breaker ( 3b ) opened

12V Trigger Connected but not activated

Preamp or source unit is not on

Connections in rear are loose

Input ( 1 ) or Output ( 2 ) connectors disconnected or loose

Speaker disconnected/ shorted Internal protection engaged

Ground loop (difference in ground voltages between components)

Problems with source unit (CD, tape, etc.) or RCA cables connecting that source unit to the preamp

Some major appliance, dimmer, halogen or fluorescent light is creating interference

Possible Solution

Plug in AC Power Cord (4 )

Reset AC Breaker ( 3b )

Turn on 12V Source Unit

Make sure whole system is on

Verify all connections on rear of amp

Verify both sets of connections on that channel

Verify connections at speaker/ cable in- tegrity. Bring to Dealer or Service Center

If cable TV is present (see Note 1)

If cable TV is not present (see Note 2)

Try different source (tuner, tape, etc.) and/or different RCA cable

Make sure all appliances, dimmers and suspect lights are off

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 to which 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 six inches 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 call your Dealer or Service Center. If the hum disappears, re-connect one RCA cable at a time to see if the specific cable or component is responsible. If any or all cables cause the hum to appear, subsitute with replacement cable(s). If hum continues to persist then the preamp or processor should be evaluated for proper operation by your Dealer or Authorized Service Center.

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