The servo circuit of this model is designed to be adjustment-free
and is automaticallyy adjusted inside IC. However, the adjustment
conditions inside IC of the focus bias, tracking balance and
tracking gain can be monitored using the test mode.
1. How to Start the Test Mode,
1) While the main power is OFF, set the OPEN/CLOSE
switch (S109) to the CLOSE (ON) position.
*
Alternately, shorting the test lands near S109 puts the
switch (S109) to the CLOSE (ON) position.
2) Insert the AC plug to the power outlet.
3) Insert a disc and chuck the disc. Press the PLAY button
(S106) to enter the PLAY state.
4) While press the PLAY MODE button (S102), connect
the test land to ground through a 5600 ohm resistor for 1
second.
S) When all the LCDS turn on, it indicates that the test
mode has started up.
*
If the machine cannot enter the PLAY statex
Press the PLAY button to enter the focus search
operation. Perform the step 4) operation while the
machine is performing the focus search operation. Then
the test mode will start.
Note)
● Once the test mode is started and the test land is
grounded through the resistor, key operations of the
machine cannot be accepted.
● While the test mode is established, the OPEN/
CLOSE switch is designed to be ignored.
2. Focus Search Mode
The focus search operation can be checked using this mode.
How to start the focus search mode:
Press the STOP button when the machine is stopped (STOP
mode).
If the STOP button is pressed again, the focus search
operation is stopped.
When a disc is inserted while the machine is in the focus
search mode, the disc does not rotate (focus servo is not
locked ON) but the search operation is repeated.
3. Focus Bias, Tracking Balance and Tracking
Gain Check
Selection of either the focus bias check mode, tracking
balance check mode or the tracking gain check mode can be
made by pressing the PLAY mode key during disc playback.
As the PLAY mode key is pressed, the check mode changes
in the following order.
Check mode OFF - Focus Bias + Tracking Balance
+ Tracking Gain
When the mode display appears on the LCD, and when the
PLAY key is pressed in the STOP mode, the LCD shows the
center value at first. Then the display changes to the set
value which is set by the automatic adjustment when the
disc starts rotation.
Focus Bias
When the machine enters the focus bias check mode, the
following display appears on LCD enabling to check the
focus bias setting level inside IC.
w
Focus bias Bias set value
The bias set value is displayed by hexadecimal notation in
the 64 steps.
Display range of set value 80 to bF
Default value (center value) of setting is displayed as
“9d”. When the value larger than the default value is
displayed, it means that the higher bias value is set to the
machine. When the value smaller than the default value is
displayed, it means that the smaller bias value is set to the
machine,
RF level check
● Test pointi TPRF & VC
“Test disc: TCD-782
Confirm that the RF waveform as shown below appears,
RF Signal Waveform
I
1.2*o.2vp-p
EYE PA~RN
VREF
must be CLEAR and MAX
VOLT/DIW 200mV
TIME/DIW 0.5pS
When the mode display appears on the LCD, and when the
PLAY key is pressed in the STOP mode, the LCD shows the
center value at first. Then the display changes to the set value
which is set by the automatic adjustment when the
disc starts rotation,
@ Focus bias control by the manual control
The focus bias value can be set to any desired value by
pressing the F. Skip key or B. Skip key during the focus
bias check mode.
The 64 steps can be set in the range from 80 to bF.
(Center value: 9d)
Make an attempt to change the focus bias using the F. Skip
key or B. Skip key while observing the RF waveform on
an oscilloscope, and confirm that the RF signal is
maximum at the default value (the value before starting
the manual operation).
When the maximum amplitude is confirmed at the default
setting, the automatic adjustment works satisfactorily.
–25–
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