Focus Bias AdjustmentFocus/Tracking Gain Adjustment
This adjustment is to be done when the optical pick-up block isA frequency responce analyzer is necessary in order to perform this
replaced.adjustment exactly.
However, this gain has a margin, so even if it is slightly off, there is
Adjustment procedure :no problem. Therefore, do not perform this adjustment.
1. Connect the oscilloscope to test point TP (VC) and Focus/tracking gain determines the pick-up follow-up (vertical andTP (RFO) on
MAIN board.horizontal) relative to mechanical noise and mechanical shock when
2. Put the set into test mode.the 2-axis device operate.
3. Optical pick-up setting to the center by ? or  buttonHowever, as these reciprocate, the adjustment is at the point where
pushing.both are satisfied.
4. Insert disc (YEDS-18) and press � button.Y When gain is raised, the noise when the 2-axis device operates
5. Press the � button. (Tracking servo ON)increases.
6. Adjust RV701 so that the oscilloscope waveform is as shoY When gain is lowered, mechanical shock and skipping occurswn in
the figure below (eye pattern).more easily.
A good eye pattern means that the diamond shape (a) in the cen-Y When gain adjustment is off, the symptoms below appear.
ter of the waveform can be clearly distinguished.
Gain
7. Release test mode after adjustment is completed.FocusTracking
Symptoms
r The time until music starts becomes
Y RF signal reference waveform (eye pattern)
longer for STOP ? � button or
automatic selection.
low low or high
( Â, ? buttons pressed.)
VOLT/DIV : 0.2 V
(Normally takes about 2 seconds.)
TIME/DIV: 500 ns
r Music does not start and disc
1.0 � 1.4 V continues to rotate for STOP ? � � low
button or automatic selection.
( Â, ? buttons pressed.)
r Sound is interrupted during PLAY.
Or time counter display stops� low
progressing.
r More noise during 2-axis device
When observing the eye pattern, set the oscilloscope for AC rangehigh high
operation.
and raise vertical sensitivity.
The following is a simple adjustment method.
[MAIN BOARD]
� Primary Adjustment �
oscilloscope
Note :Since exact adjustment cannot be performed, remember
(DC range)
the positions of the controls before performing the
adjustment.If the positions after the primary adjustment
TP (RFO)are only a little different, return the controls to the origi-
nal position.
TP (VC)Procedure :
1. Keep the set horizontal.
If the set is not horizontal, this adjustment cannot be performed
due to the gravity against the 2-axis device.
2. Insert disc (YEDS-18) and press � button.
3. Connect oscilloscope to TP (FO) and TP (VC) on MAIN board.
4. Adjustment RV702 on MAIN board so that the waveform is as
shown in the figure below. (Focus gain adjustment)
Adjustment Location : Main board (See page 12)
� 10 � |
ACEC
