Sony CDP-790 - SECTION 2 ELECTRICAL ADJUSTMENT; RF Level Check; RF PLL Free-run Frequency Check; Focus;Tracking Gain Adjustment

SECTION 2
ELECTRICAL ADJUSTMENT
1. Perform adjustments in the order given.
2. Use YEDS-18 disc (3-702-101-1) unless otherwise indicat-
ed.
3. Use the oscilloscope with more than 10MQ impedance.
RF Level Check
Procedure:
oscilloscope
(DC range)
BD board
—$—<<<—.
TP (RF) o
TP (VC) 06
1.
Connect
oscilloscope
to
test
point
TP
(RF)
and
TP
(VC)
on
BD
board.
2. Turn POWER switch on.
Put disc (YEDS-18) in and play back.
4. Confirm that RF level and eye pattern is optimum.
Oputimum eye pattern means that shape “©” can be
clearly distinguished at the center of the wave form.
ed
VOLT/DIV : 200mV
TIME/DIV : 500nS
WAY
RF signal Reference Waveform (eye pattern)
+09
wie \
HN
wn
XXX
We XN XH
NYY
XX
WY
iM
AN)
mee
Wi
Procedure :
A)
RF leve
1.2+0.3Vp-p
oscilloscope
(DC range)
BD board
mcm,
TP (TE QO) o
TP (VC) o
1. Connect test point TP (ADJ) and TP (TES) to ground
with lead wire.
2. Connect oscilloscope to test point TP (TE O) and TP
(VC) on BD board.
3. Turn POWER switch on.
4, Put disc (YEDS-18) in and play back.
5. Confirm that the oscilloscope waveform is symmetrical
on the top and bottom in relation to 0V.
6. After check, remove the lead wire connected in step 1.
Note: Take sweep time as long as possible to obtain best
waveform.
RF PLL Free-run Frequency Check
Procedure:
a counter
Main an ere
TP TP (PCK) a
1. Turn POWER switch on.
2. Put disc (YEDS-18) in and play back.
3. Confirm that reading on frequency counter is 4.3218M Hz.
Focus/Tracking Gain Adjustment
A frequency responce analyzer is necessary in order to
perform this adjustment exactly.
However, this gain cas a margin, so even if it is slightly off.
there is no problem. Therefore, do not perform this adjust-
ment.
Focus/tracking gain determines the pick-up follow-up (ver-
tical and horizontal) relative to mechanical noise and me-
chanical shock when the 2-axis device operate.
However, as these reciprocate, the adjustment is 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.
low or high
Symptoms
* The time until music starts
becmes longer for STOP ~>
PLAY or automatic selection.
(Kd, PPI buttons pressed.)
(Normally takes about 1 sec-
onds.)
* Music does not start and disc
continues to rotate for STOP
—[> PLAY or automatic selec-
tion.
(Kd, PPI buttons pressed.)
*Sound is interrupted during
PLAY. Or time counter display
stops progressing.
*More noise during 2-axis
device operation.
The following is a simple adjustment method.
—Primary Adjustment—
Note: Since exact adjustment cannot be performed,
remember the positions of the controls before perfor-
ming the adjustment.
If the positions after the primary adjustment are
only a little different, returs the controls to the
original position.
oscilloscope
(DC range)
BD board
iene
TP (FE 0)
TP (TE O) oe’
TP (VC)