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HM-54
HM-54
Appendix A: Service Information
Warranty Service
Details concerning Warranty Service are spelled out in
the Warranty section on page 15.
If you think your HM-54 has a problem, please do
everything you can to confirm it before calling for
service. Doing so might save you from the deprivation of
your headphone amp and the associated suffering.
These may sound obvious to you, but here are some
things you can check. Read on.
Troubleshooting
No Power
• Our favorite question: Is it plugged in?
• Make sure the power cord is securely seated in the
IEC socket [6] and plugged all the way into the AC
outlet.
• Make sure the AC outlet is live (check with a tester
or lamp).
• Is the POWER [5] switch on? Make sure the
POWER switch on the front panel is in the ON
position (up) and the power LED is lit.
• Are all the lights out in your building? If so, contact
your local power company to get power restored.
• If the power LED is not illuminated on the front
panel, and you are certain that the AC outlet is live,
it will be
necessary to have your HM-54 serviced.
There are no user serviceable parts inside. Refer to
“Repair” at the end of this section to find out how to
proceed.
Bad Channel
• Is the input LEVEL control [4] for the channel
turned up?
• Is the signal source turned up? Make sure the signal
level from the selected input source is high enough
to drive the line-level inputs on the HM-54.
• Try the same source signal in another channel, set
up exactly like the suspect channel.
Bad Output
• If you are listening to a PHONES OUTPUT [8] on
the rear panel, make sure that nothing is plugged
into the corresponding PHONES out on the front
panel.
• If only one side of the stereo headphones is working,
make sure you have a signal at both inputs. There
must be a signal present at both inputs [7][9][10]
to get a signal in both sides of the headphone
output.
Bad Sound
• Is the input connector plugged completely into the
jack?
• Is it loud and distorted? Make sure the input LEVEL
[4] control for the channel is set correctly. Reduce
the signal level on the input source if possible.
• If possible, listen to the signal with headphones
plugged into the input source device. If it sounds
bad there, it’s not the HM-54 causing the problem.
Noise/Hum
• If connecting an unbalanced source to the balanced
inputs on the HM-54 using a TS-to-TS 1/4" cable, it
could cause a ground loop. Refer to “Unbalancing
a Line” for more info on connecting an unbalanced
source to a balanced input.
• Sometimes it helps to plug all the audio equipment
into the same AC circuit so they share a common
ground.