Samsung DVD-611/ 511 Service Manual download pdf (Page 57)

Circuit Descriptions

5-12 Samsung Electronics

5-4-3 Operation

1) FOCUSING SERVO

(1) FOCUS INPUT

The focus loop is changed from open loop to closed loop, and the triangular waveform moves the object lens up

and down (at pin 75 of SIC1 during Focus SERVO ON.) At that time, S curve is input to pin 65 of SIC1.

ABAD (pin 39 of RIC1) signal, summing signal of PD A, B, C, D, is generated, and zero cross(2.5V) point occurs

when S curve is focused and ABAD signal exceeds a preset,constant value. The focus loop is changed to

closed loop, and the object lens follows the disc movement, maintaining a constant distance from the disc.

(these operations are same in CD and DVD).

Fig. 5-18

Vref

1.5V

Pin75 of SIC1 (FOD)

Pin65 of SIC1 (FEI)

Pin39 of RIC1 (ABCD)

(2) PLAY

When focus loop closes the loop during focus servo on, both pin 65 and pin 75 of SIC1 are controlled by VREF

voltage (approx. 2.5V), and pin 26, 27 of SIC4 are approximately 4.5V.

2) TRACKING SERVO

(1) NORMAL PLAY MODE

Œ For DVD

Composite : The signal output from PD A, B, C, D of Pick-up, the tracking error signal (pin36 of RIC1) uses the

phase difference of A+C and B+D in RIC1, and inputs to terminal 64 of SIC1. Then, it is output to SIC1 pin 76 via

digital equalizer, and applied to the tracking actuator through SIC4.

Pins 76 of SIC1 is controlled by VREF(approx. 2.5V) during normal play.

Meanwhile, DVD repeats the track jump from 1 to 4 in inner direction at normal play (because data- read speed

from disc is faster than data output speed on screen).

´ For CD, VCD

Receive the signal output through E, F of Pick-up, from RIC1. The tracking error signal is similar to DVD.

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Samsung DVD-611/ 511 Service Manual Page 57