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Discussion Starter #1
I just spend a good part of the long weekend trying to fix my father's stereo system. He has an Adcom GFA-535 amplifier with a GFP-500 tuner. Yes, both are 20 years old. This system was just moved to the cottage, to replace an even older system (Yamaha receiver). Prior to the hardware change, there was a problem with right channel output - non existent. This problem was for both A and B speaker selections. I assumed the Yamaha receiver had simply died. The installation of the Adcom equipment did not rectify the problem.

So... I replaced all the speaker wire, assuming a break somewhere. Crawling through the attic, routing wires down through the walls, up through the basement (I was not a happy camper!). Same problem (Argh!).

I disconnected everything (CD player, cassette tape deck), thinking that something was not connected properly. No fix. Checked the polarity and connections to the speakers - no issues. I reversed the speaker connections - changing from right to left. Got sound from the left, but not the right. Disconnected the speakers too and listened to the headphone sound - left channel only.

I am discouraged. I think that this is a amp/tuner issue, but why did the same problem pre-exist in with the original Yamaha set-up? Could something with the speaker set-up blow something internally in the amplifier? I checked the fuses and they seem okay. What did I miss in my checklist?
 

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This may sound overly-simplistic, but have you checked to see if the balance setting/dial on the amplifier is favouring only the left channel? It's usually the easiest solutions that are overlooked.
 

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Discussion Starter #4
Just doing a little thinking... as there are two sets of speakers connected (A and B), what would speakers with different impedance do to the amp? As the hardware is old, there is no ability to change the impedance capabilities. Could this be the source of my right channel headache?
 

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Sometimes a "dead spot" on a volume control can cause this sort of issue on older equipment. Grab the volume knob firmly and crank it up and down (all the way from min to max) many times (with the AVR off). This may "clean" the dead spot. The amp(s) may be shot and you need a repair or a new AVR.
 

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Here is my logic: If you replaced a Yamaha receiver with the Adcom tuner/amplifier, and the same problem is there, then the problem must be external to the tuner/amp. The odds would be low that the same problem existed in both the Yamaha and Adcom equipment.

Your statement, "I reversed the speaker connections - changing from right to left. Got sound from the left, but not the right. " Your original problem was that you don't have audio on the right, but by reversing the connections, and you still don't have audio on the right, would normally indicate that the speaker is blown.

However, your next statement, "Disconnected the speakers too and listened to the headphone sound - left channel only." seems to be an indication that the problem is upstream (ie. the source). What is it? I am assuming that it is a CD player, or perhaps the output of your tv?

It should be simple enough to determine if a speaker is blown, by simply swapping them around (you know that the left speaker works). I would suggest trying different sources. I once had no audio from one side of my system, and it took me a little longer than it should have to figure it out. I was feeding an optical cable to my receiver for my 5.1 audio. Turns out that the source was not encoding one of the channels. I simply changed channels and heard the audio...
 

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Discussion Starter #8
I've come to the conclusion that the amp and/or tuner must be toast. Coincidence that the previous Yamaha hardware had the same problem? I don't know.

I've pulled all connections off the hardware - including CD Player, tape deck, satellite box (music). Still have the same problem. Tried the "dead spot" volume fix (thanks 57) - unfortunately not a solution.

Looks like I'll be purchasing a new receiver as an early Christmas present!
 

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If there's a balance or any tone controls, or switches, they can also introduce "dead spots". Move everything you can move. The other day I was troubleshooting for an individual with a 1970's Pioneer receiver that the client was trying to put back into service and encountered the same thing. I can't remember which switch on the front was causing the problem (I believe it was the input selector), but a few movements back and forth solved the problem.

Of course, it could also be a faulty amp. I've had one of those too in the 40+ years...
 

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You still have not indicated what your source is. Is it the tuner? Is it the optical input? Is it a specific input? Have you tried different inputs to the amp?
 

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Discussion Starter #11
57 - I will try the dead-spot fix on all dials on the front of the tuner and amp this weekend.

Fooman - I have removed all inputs. All that remains is the tuner/amp connection and a pair of speakers. The FM and AM radio output is left channel only. This was still the case when trying a cassette, CD, and music from the satellite receiver. I've reversed the speaker connections (left to right, right to left), which changes the sound output to the right side - which eliminates a dead speaker and/or the cabling.

I'll give this another "go".
 

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Discussion Starter #12
Last attempt...

I got left and right speaker sound by doing this:

Connect left speaker to Left Speaker - A Channel
Connect right speaker to Left Speaker - B Channel

Changed the output from stereo to mono. Not ideal, but a "fix" until the tuner and amp are replaced.
 

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Hi, Are you able to open it up and clean the headphone jack contacts inside.

If not, just try inserting and removing a headphone jack a few times quickly (while the amp is off). Then see if you get any sound from the bad channel.
 

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Discussion Starter #14
I'm convinced that the tuner/amp are in need of replacement. I've even taken the covers off to see if the connection from the speaker connection to the board was loose (not). Thanks for the suggestion, but I think my patience for a fix has expired.
 

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The h/phone jack is a simple enough test. Just try using headphones - that's all.

The speaker connection goes 'thru' the h/phone jack (to allow speakers to be disconnected if h/phone is in use) and sometimes those contacts can be the culprit.
 
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