Pioneer YPM-2306ZF Service Manual page 32

YPM-2306ZF
7) DFCT (Defect) Circuit
The DFCT signal is used for detecting defects on the
mirrored disc surface. It allows monitoring from the
HOLD pin (Pin 35). It goes high when defects are found
on the mirrored surface.
The DFCT signal is generated by comparing the RF
amplified signal (which is obtained by bottom holding
the RFO signal) at a specific threshold level by the suc-
ceeding digital section.
Stains or scratches on the disc can constitute the
defects on the mirrored disc surface. Thus, as long as
the DFCT signal remains high in the LSI, the focus and
tracking servo drives are held in the current state so
that a better defect prevention may be ensured.
76
AGCI
Surface defects
RFI
HOLD
Fig.7 : HOLD OUTPUT WAVEFORM
(When surface defects are present)
32
RFO
75
20k
30k
12k
10k
PEAK DETECT
BOTTOM DETECT
BOTTOM DETECT
S/H LPF
Fig.6 : DFCT, MIRR AND 3T DETECTION CIRCUIT
8) 3TOUT Circuit
The 3TOUT signal is generated by entering disturbance
to the focus servo loop, comparing phase of fluctua-
tions of the RF signal 3T component against that of the
FE signal at that time, then converting the signal to DC
level. This signal is used for adjusting bias of the FE sig-
nal (to be described later). This signal is not output
from the LSI, thus its monitoring is not available.
9) MIRR (Mirror) Circuit
The MIRR signal shows the on track and off track data,
and is output from Pin 43.
When the laser beam is
On track : MIRR = "L"
Off track : MIRR = "H"
This signal is used on the brake circuit (to be described
later) and also as the trigger to turn on track counting
when jumping take place.
The MIRR signal is supplied to the micro computer, too,
for the protection purpose.
40k
40k
MIRR
A/D
CIRCUIT
40k 40k
DFCT
A/D
CIRCUIT
200k
20k
3T
A/D
CIRCUIT
20k
200k
73
C3T
C212
0.1µF
OFF Track ON Track
RFI
MIRR
Fig.8 : MIRR OUTPUT WAVEFORM
(When an access is made)
3
MIRR
2
HOLD