XL-DAB (serv.man2) - Sharp Audio Service Manual (repair manual). Page 9

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XL-DAB151PH
3 – 2
Although a CD is inserted and the cover is 
closed, "NO DISC" is displayed.
(1) Focus-RF system check.
Press the Tray CD Eject Button without inserting  a disc, 
and try starting the playback operation.
1. Does the pickup move to the PICKUP-IN Switch
position?
No
No
No
No
No
Sled motor.
     
Yes
2. Does the focus (lens) move up and down?
(Waveform drawing Figure 1)
3. Is the laser lit ?
Check the focus peripheral circuit.
     
Yes
Check the laser diode at U5 pin 80 and R128 peripheral circuit. 
     
Yes
4. Is the turntable rotating?
Spindle motor.
Pins 64,65 on U5 and Pins 1,2,26,27. Check the
laser diode on U5 Pins 80 and R128 peripheral circuit.
When  a disc is loaded,  start playback operation.
1. Is focus servo activated?
(Waveform drawing Figure 2)
FO
1
65
U5
Figure 1
1
65
U5
FO
RA
2
64
U5
Figure 2
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