SCD-1, SCD-777ES - Sony Audio Service Manual (repair manual). Page 13

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When the disc type has been detected, the servo adjustment values that match it and the playback mode (CD or SACD) when the player

was last turned off will be read from EEPROM (IC735). The disc layer to be played will be judged from the playback mode (CD or SACD)
and the disc type that has been read and  playback operations started.

Table 2-5. Disc Layer to be Played

Play Mode

Disc Loaded

Disc Layer to be Played

CD

CD

CD

SACD (hybrid)

SACD (SL/DL)

*SACD

SACD

CD

*CD

SACD (hybrid)

SACD

SACD (SL/DL)

* : Play Mode is changed automatically

Servo operations and sound signal playback are explained in Section 3, “Playback Operations.”

The laser for SACDs is emitted and the disc judged as SL or DL from the reflected light. Detection is completed in the time it takes to

move from middle of the disc moved in CD layer detection to its innermost part. At this time, the spindle motor rotates at a uniform speed.

The focus drive (FD) signal that drives the focus coil and the PI signal that the disc’s reflected light generates are used in detection. The

PI signal is created from the RF signal and is output in proportion to the disc’s quantity of reflected light. Based on these signal inputs, disc
type is judged using the microprocessor (IC701).

SL discs and DL discs have different reflection rates (see Table 2-4). From these differences, discs are judged as SL or DL. The PI signal

equivalent to the disc’s reflected light is detected as level “V,” and when the value is above the fixed value, the judgment “SL disc” is made.
When it is below the fixed value, the judgment “DL disc” is made.

Table 2-4. Disc Reflection Rates

Disc

Reflection Rate

Single layer

60 – 85%

Dual layer

18 – 30%

Hybrid

15 – 30%

PI

FD

PI

V: Large -> SL

V: Small -> DL

V

V