Technics SL-PS900 Service Manual

Function
‘connected to +4.8V)
' iconnected to +4.9V)
‘digital system)
4
connected to +4.9V)
«digital system)
“nunal
annected to +4.9V)
> 3etor terminal
ym
Hz) (Not used, open)
ctor (Not used,
+ 4.9V)
tion signal input
8 input
Laat {MSB first)
digital system)
(connected to +4.9V)
- 4+MHz) output
“arminal
inected to GND)
data
r MDATA
Function
‘ing output of focus
: output of focus driver
ing output of tracking
output of tracking
ring output of traverse
output of driver
-ral output
sonnect to GND)
i DIGITAL SERVO SYSTEM
The
newly-developed
digital
servo
system
is
adopted
in
the
servo
circuit
of
the
unit’s
CD
player
instead
of
the
ordinary
analog
servo
system.
1.
The
diagrams
shown
below
represent
differences
between
the
analog
servo
and
digital
servo
systems.
The
HEAD
AMP.
output
signals
(i.e.,
focus
error
and
tracksing
error
output
signals)
are
analog.
These
analog
signals
are
converted
to
the
8-bit
digital
signals
through
the
MN6650.
The
MN6650
performs
the
following
adjustments
automatically;
focus
offset,
tracking
offset,
focus
gain,
tracking
gain,
and
tracking
balance
adjustments.
The
outputs
from
the
MN6650
such
as
the
focus
coil
driving
signal,
tracking
coil
driving
signal,
and
traverse
motor
driving
signal
are
converted
to
analog
signals
again
and
sent
to
the
coils
and
motor
to
perform
proper
servo
control
for
a
disc.
ANALOG SERVO SYSTEM
GSVLY<YGSSg
6
VRs
require
adjustment
r
:
To
EMF
demodulation
Digital
audio
RF
signal
&
D/A
conv.
————=_
playback
>
i
AN8373
:
Focus
coil
Focus error
output signal
Tracking error
output signal Traverse coil
Microcomputer
DIGITAL SERVO SYSTEM
S
Only 1 VR requires adjustment (best eye adjustment)
: To EMF demodulation
RF signal & D/A conv.
AN8800 MN6650 (Digital servo processor)
Digital audio
playback
Focus coil Lens
Tracking coil >(]
Soft
microprogram
ae
processing
Microcomputer
A/D conversion
Focus error
output signal
!
|
I
|
|
|
Tracking error
output signal
Traverse coil
fom rr ae nr ee eel ' '
J (
t ' i]
I ' ‘
‘ ' i)
Lu
| SL-PS900
2. The servo processor IC MN6650 of the newly-developed digital! servo circuit automatically performs the following
adjustments which were originally adjusted manuaily in the conventional analog servo circuit:
(1) Focus offset, (2) Tracking offset, (3) Focus gain, (4) Tracking gain, and (5) Tracking balance. Therefore, you do not
have to perform the above-mentioned electrical adjustments. The unit optimizes the servo for each loaded disc.
[You must perform the best eye (PD balance) adjustment manualy.]
The following flow chart shows the sequence of automatic adjustments.
eFlow chart on automatic adjustment sequence
“Because the microcomputer precisely performs
automatic adjustments as shown in the flow chart,
it will take approx. 5 seconds to finish reading TOC
data if a used disc is eccentric one or its surface is
Temporary adjustment of focus gain warped.
Spindle motor starts rotation
No
Approx.
2.5
sec.
Does focus pull in?
Yes
Focus servo operation: ON
Tracking servo operation: ON
Temporary adjustment of tracking gain
Tracking balance adjustment
Ne Does tracking pull in?
Fine adjustment of focus gain
Yes
Fine adjustment tracking gain

Technics SL-PS900 Specifications

General

Brand	Technics
Model	SL-PS900
Category	CD Player
Language	English