TECHNICAL
DESCRIPTION
©
Cyrus
Audio
Ltd
Jun
2014
6
CD
t
Service
Manual
Issue
1
PCB
assemblies
The
following
is
a
brief
description
of
the
internal
PCBs
found
in
the
CD
t.
The
servo
PCB
is
mounted
directly
onto
the
CD
mechanism,
this
includes
the
CD
loader
motor
and
sled
drivers,
the
servo
driver
and
CD
decoder.
The
main
PCB
is
mounted
in
the
base
of
the
chassis
and
contains
the
power
supplies,
optical
and
coaxial
SPDIF
output
and
the
user
interface
microcontroller.
Disc
reading/decoder
module
and
servo
PCB
The
disc
reading
laser
pickup
is
mounted
in
a
motor
driven
slot
loader,
which
receives
its
operating
commands
via
the
servo
PCB.
The
heart
of
the
servo
PCB
is
the
CD
decoder
Integrated
Circuit
IC401.
This
is
controlled
by
software
running
on
the
main
board
micro
controller
IC701
via
an
I
2
C
Bus.
The
microcontroller
sends
high
level
commands
(e.g.
Read
TOC,
Play
track
1)
to
the
servo
PCB
via
a
communication
bus.
Disc
loading
is
controlled
by
the
microcontroller
on
the
servo
PCB.
When
a
disc
is
inserted
into
the
player
the
first
thing
that
needs
to
happen
is
that
the
Table
of
Contents
(TOC)
of
the
disc
is
read.
This
information
contains
the
start
and
end
location
of
each
track
on
the
disc
for
disc
navigation
purposes.
In
order
to
read
the
TOC
the
laser
is
switched
on
by
the
decoder
IC,
and
a
focus
ramp
is
initiated.
If
focus
is
found
then
the
disc
motor
is
switched
on
for
a
short
time,
then
the
PLL
is
switched
on
and
the
disc
is
accelerated
to
full
speed.
Once
the
speed
had
been
achieved
and
the
PLL
is
locked
onto
the
data,
the
radial
loop
is
switched
on
and
the
subcode
will
be
read
from
the
disc
and
fed
to
the
decoder.
The
focus
and
radial
positions
of
the
laser
spot
are
controlled
by
the
decoder
by
looking
at
the
diode
signals
coming
from
the
optical
pick
up
(OPU).
These
are
D1,D2,
D3
and
D4
for
focus,
R1
and
R2
for
radial.
The
error
signal
from
these
diodes
is
used
to
generate
a
PDM
signal.
This
signal
is
then
filtered
with
a
low
pass
filter
and
amplified
by
the
motor
driver
(BA5984FP)
to
move
the
actuators.
Power
for
the
laser
diode
is
supplied
directly
from
the
decoder
IC
which
monitors
laser
output
and
adjusts
the
power
accordingly.
There
is
a
single
system
clock
on
the
servo
board,
8.4672MHz.
This
is
self
‐
generated
by
the
decoder
IC.
There
are
2
main
power
supplies
to
the
servo
board,
+5V_CD
for
the
signal
processing
electronics
and
+5V_MOTOR
to
IC402
supplying
motor
and
sled
power.
The
+5V_CD
supply
is
sub
regulated
to
+3V3
and
sub
‐
sub
‐
regulated
to
+1.8V
on
‐
board
for
the
decoder
and
other
electronics.