Clear-Com MS-222 - Symptom #4: Hum or Buzz in System; Symptom #5: System Feedback; Symptom #6: LowDistorted Audio and Persistent Call Light

TROUBLESHOOTING
/ Clear-Corn
MS-222
2-Channel
Main
Station
Symptom
#4:
Hum
or buzz
in system.
CAUSE:
Inductive
pickup
caused
by close
proximity
of
Main
or Remote
station
to
power
lines
or transformers.
REMEDY:
Relocate
offending
unit.
CAUSE:
10 Ohm
chassis
ground
resistor
(R224)
is open.
REMEDY:
Check
the DC
resistance
for 10
Ohms
between
the chassis
and
pin-1
of
any
intercom
connector.
R224
is located
on
the Rear
Panel
Connector
Printed
Wiring
Board.
If this
condition
happens
it Is
because
the
system
ground
came In
contact
with something
-HOr
with
respect
to
the Main
Station
Earth
ground.
Should
this occur,
we
recommend
you
carefully
check
the system
ground
and
AC distribution
In the
area.
NOTE:
THIS
IS A POTENTIALLY
DANGEROUS
SITUATION;
IF IT
OCCURS,
A
SHOCK
HAZARD
MAY
EXIST
BETWEEN
THE
METAL
BOOM
OF
A HEADSET
AND
GROUND.
CAUSE:
inductive
pick-up
by headset
mic; check
by switching
mic
on and
off.
REMEDY:
Move mic
away from
"hum
field".
Symptom
#5:
System
feedback.
CAUSE:
Acoustical.
REMEDY:
Volume
too high
at one
station.
REMEDY:
Two or
more speaker
stations
have
mics
on simultaneously.
REMEDY:
Headset
mis-wired.
Rewire
headset
connector.
REMEDY:
Headset
laying on
table
and microphone
on. Turn
mic off.
REMEDY:
Headset
quality.
Some headsets
have poor
isolation
between
the
microphone
and earphone.
Adjust
sidetone.
CAUSE:
Electrical.
REMEDY:
Check
Termination.
REMEDY:
Check
sidetone
levels.
REMEDY:
A headset
extension
cord was
used.
Headset
extension
cords must
be
used
with great
care
and are
not recommended.
Symptom
#6:
Audio
sounds
low and
distorted
and
the Call
light stays
on.
CAUSE:
An
ultrasonic
oscillation
is
present.
REMEDY:
Headset
mis-wired.
Rewire headset
connector.
REMEDY:
A
headset
extension
cord
was used.
Headset
extension
cords
must be
used
with
great
care
and
are
not recommended.
11/90
Rev.
1.0
Page
22