Troubleshooting a down channel in your Home Theater
These steps can also be used to help isolate which device is the cause of static, popping, or other audio issues.
Before going through the following procedures make sure your problem occurs with all your source devices (blu-ray player, cable box, etc.). If it doesn't, start by trying a new interconnect cable(s) for that source device. If the issue still occurs with only that source device try a known working source device to determine if the issue lies with the source or the input on your pre-amp.
Step 1:
Start by swapping your connections, from the problem channel - to a known working channel, at the input of the amplifier only. For example, if your front left channel has no audio you will want to swap the RCA with the right channel. Again, note that you are ONLY swapping the RCAs at the inputs of the amplifier.
After doing so, does the problem stay with the original speaker or did it move?
Step 2A:
If the problem still occurs with the original speaker, your problem lies with either the amplifier, speaker or speaker wiring. To tell if the problem is with the amp channel, switch the speaker and speaker wire with a known working speaker/speaker wire at the output of the amplifier; if the problem goes away the amp channel is good and the problem is with either the speaker or speaker wire. Obviously, at this point you would want to check your speaker wire connection at the speaker and then try new speaker wire if necessary (this is almost never the cause but don't rule it out).
Step 2B:
If the problem moves, your amplifier, speaker, and speaker wire are good and the issue is upstream from the amplifier. Start by completely replacing the RCA (or XLR) cable with a known working one. If the problem still occurs, the issue is with your pre-amp (assuming you read my preamble).