Sharp XL-DK257N Service Manual page 71

(1) Focus-RF system check.
Although a CD is inserted and the cover is closed, "NO DISC" is displayed.
1. Does the pickup move?
2. Does the focus (lens) move up and down ?
(Waveform drawing Figure 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 2)
2. Is the RF waveform normal ?
(Waveform drawing Figure 3)
Press the Tray1 CD Eject Button without inserting a disc, and try
starting the playback operation.
1
FOO
9
IC1
TRO
2
10
IC1
Figure 1
FOO
1
9
IC1
RFO
5
89
IC1
TEI
4
6
IC1
Figure 2
Yes
Yes
Yes
Yes
No Sled motor (M2A).
No Check the focus peripheral circuit.
No Check the laser diode driver Q1 peripheral circuit.
No Spindle motor (M1A).
No Pins 5, 9, 94 and 95 on IC1, Pins 1, 2, 15 and 16 on IC2.
Check the laser diode driver Q1 peripheral circuit.
No If the level is not normal.
5
IC1
89
7 – 2
XL-DK257N
RFO
Figure 3