SCD-1, SCD-777ES - Sony Audio Service Manual (repair manual). Page 16

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The tilt servo is not used in playing CDs. Although the tilt servo will be turned ON when disc type is being detected, when CD playback

begins, the tilt motor will be set to the reference position and the servo turned OFF. When SACDs are played, the tilt servo is always on.

The expander’s TILT _OUT signal (Pin td of IC712) is input to the tilt motor driver (Pin 2 of IC505), controlling the ON and OFF of tilt

servo operations.

The SKEW-IN and SKEW-OUT signals detected with the optical block’s skew sensor are converted to voltage value with the I-V amp

(IC003), and tilt error (TIE/TIERR) signals amplified with the tilt amp (IC004) are generated.

The TIE signal is compared with the reference voltage using the tilt comparator (IC506). If it is below the specified value, tilt drive output

is muted. If the TIE signal is above the specified value, Q508 is turned OFF and the tilt motor driver (IC505) is driven.

At this time, the TIERR signal, which is the actual error signal, is input to the tilt motor driver (IC505), driving the tilt motor.

The CD-PD1 and CD-PD2 signals detected with the optical block are input to the RF amp (IC001). The CDRFDC signal calculated within

the RF amp is output from the CDRFDC terminal (Pin yf of IC001), subjected to DC cutting, and input to the CDRF terminal (Pin yd of
IC001). This signal is equalized (EQ) and subjected to auto gain control (AGC) within the RF amp and is then output from the SIGO terminal
(Pin tj of IC001).

The RF signal input to the ARP’s RFIN1 terminal (Pin q; of IC702) is subjected to A/D conversion. EFM decoding and de-interleaving

are done using 16-bit DRAM (IC707), and a 16-bit sound signal is output from the DADT terminal (Pin <z/n of IC702). In addition, sub-code
signals are also decoded within ARP.

The 16-bit sound signals are encoded in Digital Audio Interface format within the ARP, and signals for digital output are output from the

DOUT terminal (Pin <z/. of IC702). The DOUT signal is output to the coaxial digital output terminal via the buffer (IC729), switch (IC732),
waveform restorer (IC990). It is then output again to the optical-digital output terminal through the optical transceiver (IC991).

When an SACD is played, the switch (IC732) is changed with the expander’s MODE terminal (Pin td of IC711), and the DOUT signal is

muted.

In addition, when CD DIGITAL OUT switch (IC1004) input is detected with the display microprocessor’s KEY 0 terminal (Pin rf of

IC1001), the switch (IC732) is similarly changed with the expander’s MODE terminal (Pin td of IC711), turning digital terminal output for
CDs ON or OFF.

The 16-bit sound signal output from the ARP’s DADT terminal is input to the digital filter’s DATAI (Pin rk of IC301 ) terminal through

the inverter (IC725) and transmitter (IC771). Using the expander’s MODE signals (Pin td of IC711), digital filter operations are switched to
correspond to CDs or SACDs. When a CD signal is played, Variable Coefficient digital filter processing is done.

In keeping with the Variable Coefficient digital filter mode set with the CD FILTER button (S1005), digital filter cut-off characteristics are

set and processed with the serial data input (Pin ed of IC301) from the microprocessor.

In the digital filter, the input digital sound signal is subjected to x64 oversampling and noise shaping. The 8 pieces of pulse code data for

every 4 bits (NSDOR1 to 4 and NSDOL1 to 4) are output to the pulse generator (IC302).

The pulse code data output from the digital filter is input to the synchronous time accuracy controller (S-TACT) pulse generator (IC302),

and pulse waveform output with low digital operation noise is generated. From this, +/- sound output for one channel and the four comple-
mentary outputs for each (for two channels, a total of eight) is input to the current pulse D/A converters (IC101 and IC201).

Because the voltage pulse signals output from the pulse generator do not include voltage fluctuations from switching, they are converted

to current pulse signals that have switched the rated current source stabilized with the current pulse D/A converters (IC101 and IC201).

The +/- sound output is synthesized and subjected to high-pass noise cutting with ladder filters (C107 and C207). They are then restored

to voltage output via the I/V conversion amps (IC102 and IC202) and subjected to differential synthesizing again.