Sony ICF-CD820 - Cd/am/fm Stereo Clock Radio, Service Manual

Page: 12 / 33

– 12 –
Focus 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 gain determines the pick-up follow-up (vertical and hori-
zontal) 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 posi-
tions of the controls before performing the adjustment. If the posi-
tions after the primary adjustment are only a little different, return
the controls to the original position.
Connection:
• The time until music starts becomes longer for
STOP
→
PLAY or automatic selection.
(
=
,
+
buttons pressed.)
(Normally takes about 2 seconds.)
• Music does not start and disc continues to
rotate for STOP
→
PLAY 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
Symptoms
low
–
–
high
Procedure:
1. Keep the set horizontal.
If the set is not horizontal, this adjustment cannot be per-
formed due to the gravity against the 2-axis device.
2. Insert the disc (YEDS-18) and press
^
button.
3. Connect the oscilloscope TP (FE) and TP (VREF) on MAIN
board.
4. Adjustment RV502 on MAIN board so that the waveform is
as shown in the figure below.
• Incorrect Examples (DC level changes more than on adjusted
waveform)
MAIN board
TP (FE)
TP (VREF)
+
–
oscilloscope
)
(
VOLT/DIV: 100 mV
TIME/DIV: 2 mS
100 mV
0 V
VOLT/DIV: 100 mV
TIME/DIV: 2 mS
200 mV
0 V
VOLT/DIV: 100 mV
TIME/DIV: 2 mS
75 mV
0 V
low focus gain
high focus gain