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Appendix A: Service Information
If you think your HM-4 4-Way Headphone Amplifier has a
problem, please check out the following troubleshooting tips and
do your best to confirm the problem. Visit the Support section of
our website (www.mackie.com/support) where you will find lots
of useful information such as FAQs and other documentation.
You may find the answer to the problem without having to part
with your HM-4 4-Way Headphone Amplifier.
Troubleshooting
No power
• Our favorite question: Is it plugged in? Make sure
the included power adapter is securely fastened
to both the HM-4 and AC outlet.
• Is the power LED on the front panel illuminated?
No sound
• Are the phones level knobs turned all the way down?
Verify that all the phones level knobs on the HM-4
are properly adjusted.
• Is the level knob for the input source turned all the way
down? Verify that all the volume controls in the system
are properly adjusted. Look at the level meter to ensure
that the mixer is receiving a signal.
• Is the signal source working? Make sure the connecting
cables are in good repair and securely connected at both
ends. Make sure the output level control on the mixing
console is turned up sufficiently.
• Make sure the mixer does not have a mute on or a
processor loop engaged. If you find something like this,
make sure the level is turned down before disengaging
the offending switch.
Poor sound
• Is it loud and distorted? Make sure that you're not
overdriving a stage in the signal chain. Verify that
all level controls are set properly.
• Be sure all connections are secure.
6
HM-4 4-Way Headphone Amplifier
Hum
• Use balanced connections throughout your system
for the best noise rejection.
• Whenever possible, plug all the audio equipment's line
cords into outlets which share a common ground.
The distance between the outlets and the common
ground should be as short as possible.
Repair
For warranty service, refer to the warranty information
on page 9.
Non-warranty service is available at a factory-authorized
service center. To locate the nearest service center, visit
www.mackie.com/support/service-locator. Service for
HM-4s living outside the United States may be obtained through
local dealers or distributors.
If you do not have access to our website, please call our Tech
Support department at 1-800-898-3211 (normal business hours,
Pacific Time), to explain the problem. They will tell you where
the nearest factory-authorized service center is located in your
area.
Please write the serial numbers here for future reference
(i.e., insurance claims, tech support, return authorization,
make dad proud, etc.)
Purchased at:
Date of purchase:
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