Electrical Adjustmens - Sony D-EJ750 Service Manual

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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.
VOLUME button : Minimum
HOLD switch : OFF
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ELECTRICAL ADJUSTMENTS
(J401)
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D-EJ750/EJ751/EJ753/EJ755/EJ756CK/EJ758CK
SECTION 4
2 9
8
Focus bias Check
Condition:
• Hold the set in horizontal state.
Connection:
oscilloscope
(AC range)
[MAIN BOARD] (SIDE A)
Q Q
3 6 7 1 3 1 5
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)
VOLT/DIV : 100 mV (With the 10 : 1 probe in use)
TIME/DIV : 500ns
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.
co
.
9 4 2 8
TP630(RF)
0 5 8 2 9 9 4 2 8
RF level
0.45 to 0.65 Vp-p
m
9 9
9 9
7