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JVC CA-C55BK - Laser Pickup Maintenance and Replacement; Laser Diode Life, Drive Current, and APC Adjustment; Laser Pickup Replacement Procedure

JVC CA-C55BK
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Maintenance
of
Laser
Pickup
(1)
Life
of
the
laser
diode
(Fig.
1)
When
the
life
of
the
laser
diode
has
expired,
the
following
symptoms
will
appear.
1.
The
level
of
RF
output
(EFM
output:
amplitude
of
eye
pattern)
will
be
low.
'
XT-C55BK
|
|
i
Is
RF
output
0.5£0.15Vp-p?
Replace
it.
(Note)
To
observe
RF
for
examination
of
the
laser
deterioration,
not
the
lead
of
C823
but
pin7
of
IC830
(one
2.
The
drive
current
required
by
the
laser
diode
Bide
GEOR
OS)
must
Be
Dad:
will
be
increased.
In
such
a
case,
check
the
life
of
the
laser
diode
following
the
flowchart
below.
Is
the
laser
diode
drive
current
less
than
120mA?
Replace
it,
(2)
Measurement
of
laser
diode
drive
current
(Fig.2)
Replace
the
jump
wire
(W212)
shown
below
with
the
resistor
(1).
>
Disconnect
right
lead
of
R830
and
R843
to
connect
W212,R830
and
R843
as
followings.
Measure
the
voltage
across
the
resistor
(1Q)
with
©
(Fig.
1)
a
milli-voltmeter.
When
the
voltage
is
more
than
120mV,
it
shows
that
the
life
of
the
laser
diode
has
ae
ENA-149
7101
(3)
Semi-fixed
resistor
on
the
APC
PC
board
The
semi-fixed
resistor
on
the
APC
printed
circuit
board
which
is
attached
to
the
pickup
is
used
to
adjust
the
laser
power.
Since
this
adjustment
should
be
performed
to
match
the
characteristics
of
the
whole
optical
block,
do
not
touch
the
semi-fixed
resistor.
If
the
laser
power
is
lower
than
the
specified
value,
the
laser
diode
is
almost
worn
out,
and
the
laser
pickup
should
be
replaced.
If
the
semi-fixed
resistor
is
adjusted
while
the
pickup
is
functioning
normally,
the
laser
pickup
may
be
damaged
due
to
excessive
current.
FRONT
Nem
mee
we
eee
eee
ee
Ke:
P---ccfrccccccc
(
(Fig.2)
Replacement
of
Laser
Pickup
Turn
off
the
power
switch
and,
disconnect
the
power
cord
from
the
ac
outlet.
Check
the
eye-pattern
at
pin10
of
IC830
(lead
of
C823).
Replace
the
pickup
with
a
normal
one.
(Refer
to
”Pickup
Removal”
on
the
previous
page)
Plug
the
power
cord
in,
and
turn
the
power
on.
At
this
time,
check
that
the
laser
emits
for
about
3seconds
and
the
objective
lens
moves
up
and
down.
Note:
Do
not
observe
the
laser
beam
directly.
(No.20474)
3-19

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