Yamaha RX-V781 Owner's Manual page 136

Problem
No sound from the playback device (connected to the
unit with HDMI).
No sound from the playback device (when HDMI
Control is used).
No sound from the TV (when HDMI Control is used).
Only the front speakers work on multichannel audio.
Noise/hum is heard.
The sound is distorted.
Cause
The TV does not support HDCP (High-bandwidth Digital Content
Protection).
The unit is set not to output audio input through HDMI jacks from the
SPEAKERS terminals.
The number of devices connected to the HDMI OUT jack exceeds the
limit.
The TV is set to output audio from the TV speakers.
TV audio is selected as the input source.
The TV is set to output audio from the TV speakers.
A TV that does not support ARC is connected to the unit only with an
HDMI cable.
(If the TV is connected to the unit with an audio cable)
The TV audio input setting does not match the actual connection.
(If you are trying to use ARC)
ARC is disabled on the unit or TV.
The playback device is set to output 2-channel audio (such as PCM) only.
The unit is too close to another digital or radio frequency device.
The cable connecting the unit and playback device is defective.
The volume of the unit is too high.
A device connected to the unit's output jacks is not turned on.
En
Refer to the instruction manuals for the TV and check the TV's specifications.
In "Audio Output" in the "Setup" menu, set "Amp" to "On" (p.118).
Disconnect some of the HDMI devices.
Change the audio output setting on your TV so that the playback device audio is output
from the speakers connected to the unit.
Select an appropriate input source with the input selection keys.
Change the audio output setting on your TV so that the TV audio is output from the
speakers connected to the unit.
Use a digital optical cable to make an audio connection (p.33).
Use "TV Audio Input" in the "Setup" menu to select the correct audio input jack (p.117).
Set "ARC" in the "Setup" menu to "On" (p.118). Also, enable ARC on the TV.
To check it, use "Audio Signal" in the "Information" menu (p.127). If necessary, change
the digital audio output setting on the playback device.
Move the unit further away from the device.
If there is no problem with the connection, replace with another cable.
Turn down the volume. If "ECO Mode" is set to "On", set it to "Off" (p.125).
Turn on all devices connected to the unit's output jacks.
136
Remedy