Sony PS-X65 - Page 6

~PS-X65 |
5. Drop-point and End Detection (see Fig. 5 and 6):
When S504 (AUTO START) is turned on, the
tonearm moves toward the disk.
The presence of a drop-point on the disk is deter-
mined by counting slits of the movable shutter ro-
tating with the tonearm.
The end of a disk is also detected by counting
slits of the movable shutter. After detecting the end,
the tonearm returns.
Slits are counted as follows. The light emitted
by D401 and D402 strike on the movable shutter.
If the light from D401 (D402) passes a slit, it turns
on Q301 (Q302). The outputs of Q301 and Q302
are fed to the Schmitt circuit consisting of IC103,
where the waveforms are shaped. The shaped outputs
are applied to terminals (32) and (33) of IC102.
Also, whether the tonearm is moving forward
or backward is determined by comparing the phases
of the signals from terminals (32) and (33) of IC102.
ee ee ee ex = ae Slit of movable
shutter
fixed slit A — — — = fixed slit B
phase difference: 90°
slit
B
eo
eae
(FORWARD)
*
aa
a
|
slitB
(BACK)
Fig. 5
0401
Fig. 6