Yamaha CX-A5100 Owner's Manual page 162

Problem
The unit cannot be controlled using the remote
control.
External devices cannot be controlled using the
remote control.
The remote control does not learn new functions.
Cause
The unit is out of the operating range.
The batteries are weak.
The unit's remote control sensor is exposed to direct sunlight or
strong lighting.
The remote control is set to control external devices.
The remote control IDs of the unit and the remote control are not
identical.
The remote control is set to control the unit.
The corresponding remote control code is not set properly.
The batteries of the remote control of the unit and/or the external
device are weak.
The distance between the two remote controls is not appropriate.
The signal coding or modulation of the other remote control is not
compatible with the remote control.
Memory capacity is full.
En
Remedy
Use the remote control within the operating range (p.5).
Replace with new batteries.
Adjust the lighting angle, or reposition the unit.
Press SOURCE/RECEIVER to set the remote control to control the unit (the key
lights up in orange).
Change the remote control ID of the unit or the remote control (p.146).
Press SOURCE/RECEIVER to set the remote control to control external devices
(the key lights up in green).
Set the remote control code again (p.149). Even if the remote control code is
registered properly, some products may not respond to the remote control.
Replace with new batteries.
Place the remote controls at a proper distance (p.152).
Learning is impossible in this case.
Clear unnecessary assignments to free some memory space for new functions
(p.158).
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