Sony PMC-107 Service Manual page 17

Focus Bias Adjustment
This adjustment is to be done when the optical pick-up block is
replaced.
Procedure :
CD board
TP (RF)
TP (VC)
1. Connect the oscilloscope between TP (RF) and TP (VC).
2. Insert disc (YEDS-18) and push the fl button.
3. Adjust RV701 so that the oscilloscope waveform is maximum as
shown in the figure below (eye pattern).
• RF signal reference waveform (eye pattern)
When observing the eye pattern, set the oscilloscope for AC range
and raise vertical sensitivity.
Adjustment Location : See page 19.
oscilloscope
(DC range)
VOLT / DIV : 0.2 V
TIME / DIV : 500 nS
1.3 ± 0.2 V
0V
– 17 –
REFERENCE
Focus/Tracking Gain Adjustment
A frequency response 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 raised, the noise when the 2-axis device operates
increases.
• When gain is lowered, it is more susceptible to machanical shock
and skipping occurs more easily.
When gain adjustment is off, the symptoms below appear.
Symptoms
• The time until music starts becomes longer
for π m fl on automatic selection.
, ±
(≠ buttons pressed.)
(Normally, takes about 2 seconds.)
• Music does not start and disc continues
to rotate for π m fl or automatic
selection.
, ±
(≠ buttons pressed.)
• Sound is interrupted during PLAY. Or
time counter display stops progressing.
• More noise during 2-axis device
operation.
Gain
Focus Tracking
low low or high
– low
– low
high high