Sharp MD-M3 Service Manual page 59

(2) Tracking system check
Check the TE waveform at pin 18 on IC1.
If the waveform shown in Figure 59-1 appears and soon after
NO DISC appears.
"IL" is possible, but play is not possible.
"IL" is not possible.
(3) Spin system check
Press the LID switch without inserting a disc, and then try
starting the play operation.
1. The turntable rotates a little. (Waveform drawing 59-2)
2. The turntable doesn't rotate.
The tracking servo is not activated.
Check the peripheral circuits at pins 18 and 19 on IC1, pin 23 on
IC2, and CNS2.
A normal jump operation cannot be completed or the beginning of
the track cannot be found.
Check the around pin 23 on IC2.
Data cannot be read. Check the VCO-PLL system.
T
Stopped
CH1=10V CH2=1V
DC 10:1 DC 10:1
TE
2
DRF
T
1
=Filter= =Offset=
Smoothing : ON CH1 :
BW : FULL
CH2 :
CH3 :
CH4 :
The spin driver circuit is OK.
Check around pin 25 on IC2, pins 7 and 8 on IC3, and CNS3.
T
Stopped
CH1=200mV CH2=500mV
DC 10:1 DC 10:1
T
FDO
2
SPDO
1
=Filter= =Offset=
Smoothing : ON CH1 :
BW : FULL CH2 :
CH3 :
CH4 :
– 59 –
MD-M3/M1
100ms/div
(100ms/div)
NORM:100kS/s
=Record Length= =Trigger=
0.0V Main : 100K Mode : NORMAL
0.00V Zoom : 2K Type : EDGE CH1
0.00V Delay : 2.924ms
0.00V Hold off : 0.2us
Figure 59-1
1999/04/07 09:51:15
500ms/div
(500ms/div)
NORM:20kS/s
=Record Length= =Trigger=
0.000V Main : 100K Mode : NORMAL
0.000V Zoom : 2K Type : EDGE CH2
0.00V Delay : 2.924ms
Hold off : 0.2us
0.00V
Figure 59-2