Yamaha M-5000 Owner's Manual page 31

Problem
The sound is suddenly
muted.
There is a lack of bass
and no ambience.
A "humming" noise is
heard.
Cause
The protection circuitry has
been activated because of a
short circuit, etc.
The speakers are not connected
properly.
The + and − wires are connected
in reverse at the amplifier or the
speakers.
Both balanced and unbalanced
cables are being used
simultaneously between two
components.
Remedy
Make sure that the speaker wires are
not touching each other or shorting out
against the rear panel of the unit, and
then turn on the power to the unit.
Make sure that the speakers are
connected properly. If the problem
persists, the cables might be defective.
Connect the speaker wires to the correct
+ and − polarity.
Do not use both balanced and
unbalanced cables simultaneously
between two components. Doing so
would create a ground loop that could
generate static and noise.
See
page
16
16
15
12
31