I have a dead channel in this wonderful receiver. Has anyone ever diagnosed a similar problem? Any ideas regarding how to proceed?
Thanks for those suggestions. I will certainly give that recommended procedure a try.
If the unit is producing sound on one channel but not the other, this would at least indicate that the unit is not going into protect mode. You could have issues in more than just the output transistors. To determine if the problem is in the output stage or pre-stage, you can do couple of tests. You will need to have access to another amplifier source with a speaker of sorts. A amplified computer speaker works well. You want to check sound coming out of both the "Tape 1 rec out" jacks and the "pre-out" jacks ( you will need to remove the U jumpers from the plugs to check.
If you're using the computer speaker, they usually have a 3.5mm stereo jack to connect for audio. You will need to adapt that plug to a Y adapter that has two RCA male plug ends to plug into the jacks on the rear of the unit. For testing, be sure to use one plug at a time to check L/R output !
First test is to plug your test speaker/amp into the "pre-out"..If you have audio on both channels, then stop with testing and the test has determined your problem is in the final stages/bias/pre/output...If you still do not have audio in the one channel at the "pre-out" , check the audio on the "tape 1 rec out" jacks. If you have audio on both jacks there, then you have an issue in the AF control/ volume or something in the switching stages. If audio is still missing , then you have something the switching stages or the front-end circuitry.
The basic checks or repairs are to check the headphone jack, speaker selector switches and cleaning the volume and balance controls. A dirty/oxidized control by itself can cause loss of audio on one channel...
Sounds like you have bad output transistors. Download the service manual from this site and locate the output transistors then check the web on how to test them. I have had a couple of these units and two had no sound from the left or right channels or distorted sound when you turned up the volume and it turned out to be bad output transistors. If your not comfortable working on this unit take it to a good tech in your area. good luck.
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