Sharp CD-BA250 Service Manual page 40

CD-BA250/CD-BA2600
(1) Focus-HF system check
Although a CD is inserted and the cover is closed, "NO
DISC" is displayed.
Press the OPEN/CLOSE switch (SW1) without inserting a
disc, and try starting the playback operation.
1. Does the pickup move to the PICKUP-IN Switch (SW4)
position ?
2. Does the focus (lens) move up and down ?
(Waveform drawing Figure 40-1).
3. Is the laser lit ?
4. Is the turntable rotating ?
When a disc is loaded, start playback operation.
1. Is focus servo activated ? (Waveform drawing Figure 40-2)
2. Does DRF change from "L" to "H" ?
3. Is the HF waveform normal ?
Figure 40-3)
Stopped
CH1=500mV CH2=10V
DC 10:1 DC 10:1
FDO
1
T
DRF
2
TE
3
CH Position To
-3div -1div 0div
=Filter= =Offset=
Smoothing : ON CH1 : 0.000V
BW : FULL
CH2 : 0.0V
CH3 : 0.00V
CH4 : 0.00V
Figure 40-2
Yes
Yes
Yes
Yes
No
Is the disc rotating ?
Yes
(Waveform drawing
CH3=1V 500ms/div
DC 10:1 (500ms/div)
NORM:20kS/s
CH2
Position
0.20div
+1div +3div
=Record Length= =Trigger=
Main : 100K Mode : AUTO
Zoom : 2K Type : EDGE CH1
Delay : 0.0ns
Hold off : 0.2 s
Stopped
CH1=500mV
DC 10:1
T
FDO
1
TDO
3
=Filter=
Smoothing : ON
BW : FULL
No
Sled motor (M2)
No
Check the focus peripheral circuit.
No
Check the laser diode driver Q1 peripheral circuit.
No
Spindle motor (M1).
No
Pins 7~12, 79 and 80 on IC1
Check the laser diode driver Q1 peripheral circuit.
No
Check the spin system.
If the disc is spinning and a HF waveform is generated,
DRF will go H.
No
If the level is not normal.
– 40 –
CH3=500mV
DC 10:1
=Offset= =Record Length= =Trigger=
CH1 : 0.000V Main : 100K Mode : AUTO
CH2 : 0.0V Zoom : 2K Type : EDGE CH1
CH3 : 0.000V Delay :
Hold off :
CH4 : 0.00V
Figure 40-1
Vp-p=1.0V~1.3V
0.5mV/div,0.5 sec/div
Figure 40-3
500ms/div
(500ms/div)
NORM:20kS/s
CH1
v/DIV
500mV
0.0ns
0.2 s