Reference - Sony CFD-V27 Service Manual

Focus Bias Check
This check is to be done when the optical block replaced.
Check Procedure:
1. Connect the oscilloscope to test point TP (VC) and TP (RF) on
MAIN board.
2. Put the set into test mode.
3. Opitical pick-up setting to the center by + or – button pushing.
4. Insert disk (YEDS-18) and press ^ button.
5. Press the MODE button. (Tracking servo ON)
6. Check that the oscilloscope wavewform is as shown in the figure
below (eye pattern).
A good eye pattern means that the diamond shape ( ) in the
center 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 sensivity.
[MAIN BOARD] (Conductor side)
VOLT/DIV : 0.2V
TIME/DIV : 500ns
0.9Vp-p – 1.3Vp-p
Oscilloscope
(DC range)
TP
(RF)
+
–
TP(VC)
— 15 —
5-4.

REFERENCE

Focus/Tracking Gain Check
Adjustment Location : MAIN board (Component side)
A frequency response analyzer is necessary in order to perform this
check exactly.
However, this gain has a margin, so even if it is slightly off, there is
no problem.
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.
Gain
Symptoms
• The time until music starts
becomes longer for STOP
CD ^ or automatic
selection (0 , ) buttons
pressed). (Normally takes
about 2 seconds.)
• Music does not start and disc
continues to rotate for STOP
CD ^ or automatic
selection (0 , ) buttons
pressed.)
• Sound is interrupted during
PLAY. Or time counter
display stops progressing.
• More noise during 2-axis
device operation.
Check Procedure:
1. Keep the set horizontal.
2. Inset disk (YEDS-18) and press ^ button.
3. Connect an oscilloscope to TP (FE) and TP (VC) on the MAIN
board.
4. Check that the waveform is as shown in the figure below. (Focus
waveform)
(See page 16)
Focus Tracking
low low or high
— low
— low
high high