– 7 –
SECTION 4
ELECTRICAL CHECKING
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
AVLS switch
: NORM
HOLD switch
: OFF
Checking Location:
– MAIN board (Side A) –
Focus bias Check
Condition:
• Hold the set in horizontal state.
Connection:
Procedure:
1. Connect the oscilloscope to the test points TP601 (RF) and
TP404 (GND) on the MAIN board.
2. Set a disc. (YEDS-18)
3. Press the
u
button.
4. Check the oscilloscope waveform is as shown below.
A good eye pattern means that the diamond shape (
◊
) in the
center 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 : 500 ns
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.
oscilloscope
(AC range)
+
–
MAIN board
TP601 (RF)
TP404 (GND)
2 k
Ω
RF level
0.35 to 0.55 Vp-p
TP601
(RF)
TP404
(GND)
