Marantz MM9360 - Manual (Page 8)

8
7. REPAIRS
Only the most competent and qualified technicians should
be allowed to service your unit. Marantz and its factory
trained warranty station personnel have the knowledge and
special equipment needed for repair and calibration of this
precision instrument.
In the event of difficulty, call the toll-free telephone num-
ber listed on the face of the warranty to obtain the name
and address of the Marantz Authorized Service Center
nearest you. Please include the model, serial number of
your unit together with a copy of your purchase receipt and
a full description of what you feel is abnormal in its behav-
ior.
8. TROUBLESHOOTING
8.1 No Audio Output
1.) Power LED not lit:
Unit may be in stand-by mode if connected to com-
patible Marantz product's stand-by output control. Line fuse
is blown or power outlet is dead.
IF LINE FUSE HAS FAILED, REPLACE ONLY
WITH SAME TYPE AND RATING FUSE.
2.) Power LED is lit but Protect LEDs stay on:
Amp module is in protect mode. Speakers have
been internally disconnected from amplifier output and con-
nected to ground until the protect fault is corrected. Out-
put overcurrent, overvoltage and undervoltage faults will
reset in about eight seconds once the fault condition is
removed, while excessive DC offset or high frequency faults
take about 30 seconds to reset.
Low Speaker Impedance: The amplifier may go
into self-protect at high output levels if the actual speaker
load impedance is much less than 4 ohms. To calculate
speaker impedance for a given combination of direct-
coupled speakers, use Ohm's law as applied to series and/
or parallel resistor networks, where each speaker (for this
purpose) can be thought of as a single resistor, using DC
resistance measurements.
Simply stated, speakers connected in series will
add together their impedance. Conversely, two speakers
connected in parallel will result in half the impedance, three
parallel speakers a third the impedance, four speakers a
fourth, and so on, assuming the speaker impedances are
all the same. Don't use mismatched impedances in paral-
lel. When using paralleled speakers, the available ampli-
fier power for that channel is evenly divided among speak-
ers, so 100 watts driving two parallel speakers of equal
impedance provides 50 watts to each speaker, etc.
3.) Thermal LED and Protect LEDs stay on:
An amplifier module is in thermal protect mode
and needs to cool. The fan will continue to run while in
thermal protect, and other modules will continue to func-
tion.
4.) Power LED lit but no Signal LED activity
There is no input signal applied or input level controls are
turned down.
8.2 Distorted Sound
1.) Clip LED is flashing regularly
Amplifier is being overdriven. Turn down the input level
control, or reduce the output level from the signal source.
2.) Clip LED is not flashing at all
Amplifier input signal may be exceeding input headroom,
which is greater than +12dBu, or 3.4V rms (measured us-
ing continuous 1kHz sine wave). Incoming signal level
higher than +12.8 dBu will cause distortion in the ampli-
fier. Turning down the input level controls will not elimi-
nate distortion if the input headroom is exceeded. Turn
down the output level of the device driving the amplifier
instead.
Additionally, an input signal may already be distorted be-
fore it gets to the amplifier. Check to see if a piece of
equipment in the signal chain before the amp is clipping.
For best performance, the amplifier should be operated
with input levels fully CW. Also check for damaged speaker
drivers that could cause distorted sound.
8.3 Hum or Buzz Noise
Be sure that the power cord’s 3-prong plug is connected to
a properly earth-grounded outlet. Lifting the grounding third
prong may not improve hum or buzz and can create a po-
tential shock hazard.
Hum is usually caused by ground currents flowing between
different pieces of equipment. Ground currents can be
minimized by using a single point AC ground for the sound
system, and by using balanced connections with quality
cable throughout the audio path.
Buzz, as well as certain audible high frequency tones, can
be caused by environmental emissions such as lighting
dimmers, neon lights, or computer equipment. Use bal-