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