Pioneer YPM-2306ZF Service Manual - Page 30

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YPM-2306ZF

2) RF Amplifier and RFAGC Amplifier

The photo-detector outputs (A + C) and (B + D) are

added, amplified and equalized on this LSI and then

output to the RFI terminal as the RF signal. (The eye

pattern can be checked by this signal.)

The RFI voltage low frequency component is :

RFI = (A + B + C + D) × 3.2

RFI is used on the FOK generator circuit and RF offset

adjusting circuit.

R207 is an offset resistor for maintaining the bottom

reference voltage of the RFI signal at 1.5 VDC. The D/A

output used for the RF offset adjustment (to be

described later) is entered via this resistor.

After the RFI signal from Pin 77 is externally AC cou-

pled, entered to Pin 76 again, then amplified on the

RFAGC amplifier to obtain the RFO signal.

The RFAGC adjustment function (to be described later)

built-in the LSI is used for switching feedback gain of

the RFAGC amplifier so that the RFO output may go to

1.5 ± 0.3Vpp.

The RFO signal is used for the EFM, DFCT, MIRR and

RFAGC adjustment circuits.

CN101

10k

A+C

B+D

10k

C216 3pF

R204

R205

10k

C217

27pF

R206

R207

1.8k

12k

RFI

D/A

10k

16k

10k

16k

Fig.3 : RFAMP, RFAGC AND FOK CIRCUIT

3) RFOK Circuit

This circuit generates the signal that is used for indicat-

ing the timing of closing the focus or state of the focus

close currently being played. This signal is output from

Pin 2 as the FOK signal. It goes high when the focus

close and in-play.

The RFOK signal is generated by holding DC level of the

RFI at its peak with the succeeding digital section, then

comparing it at a specific threshold level. Thus, the

RFOK signal goes high even if the pit is absent. It indi-

cates that the focus close can take place on the disc mir-

ror surface, too.

This signal is also supplied to the micro computer via

the low pass filter as the FOK signal and used for the

protection and the RF amplifier gain switching.

C215

C213

0.1µF

3900pF

AGCI

RFO

12k

10k

FOK

A/D

CIRCUIT

TO EFM

CIRCUIT

FOK