7
D-EJ750/EJ751/EJ753/EJ755/EJ756CK/EJ758CK
Focus bias Check
Condition:
• Hold the set in horizontal state.
Connection:
Procedure:
1. Connect the oscilloscope to the test point TP630(RF) on the
MAIN board.
2. Set a disc. (YEDS-18)
3. Press the
>B
button.
4. Check the oscilloscope waveform is as shown below.
A good eye pattern means that the diamond shape (
◊
) in the cen-
ter of the waveform can be clearly distinguished.
RF Signal reference Waveform (Eye Pattern)
To watch the eye pattern, set the oscilloscope to AC range and
increase the vertical sensitivity of the oscilloscope for easy
watch-ing.
5. Stop revolving of the disc motor by pressing the
x
button.
C412
1
3
4
5
R6
C601
IC601
L602
L409
10
R408
R627
L601
9
D461
C604
C603
C602
R601
C630
C631
C629
C632
C633 C634
C635
R631
TP630
(RF)
R632
R633
R634
R635
R636
R637
R638
R639
R640
R624
C620
C615
C616
C617
C618
R618
R619
R620
R621
R622
R623C619
IC402
C60
L302
R463
C461
C462
R461
R462
C607
C608
C626
C610
C621
C622
R625
C612
R616
17
611
C613
C627
R1
R615
L605
R432
C624
R317
R433
L606
Q409
C438
120
31
60
61
90
91
TP630(RF)
oscilloscope
(AC range)
SECTION 4
ELECTRICAL ADJUSTMENTS
The CD section adjustments are done automatically in this set.
Precautions for Check
1. Perform check in the order given.
2. Use YEDS-18 disc (Part No.: 3-702-101-01) unless otherwise
indicated.
3. Power supply voltage requirement : DC4.5 V in DC IN jack.
(J401)
VOLUME button : Minimum
HOLD switch : OFF
[MAIN BOARD] (SIDE A)
RF level
0.45 to 0.65 Vp-p
VOLT/DIV : 100 mV (With the 10 : 1 probe in use)
TIME/DIV : 500n
s
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