Pioneer YPM-2106ZF Service Manual - Page 32

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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.

AGCI

Surface defects

RFI

HOLD

Fig.7 : HOLD OUTPUT WAVEFORM

(When surface defects are present)

RFO

20k

30k

12k

10k

PEAK 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

MIRR

A/D

CIRCUIT

40k

DFCT

A/D

CIRCUIT

200k

20k

A/D

CIRCUIT

20k

200k

C3T

C212

0.1µF

OFF Track

ON Track

RFI

MIRR

Fig.8 : MIRR OUTPUT WAVEFORM

(When an access is made)

MIRR

HOLD