Daewoo DDT-21H9ZDF(21"), Руководство по обслуживанию

Страница: 74 / 116

73
CIRCUIT OPERATIONAL DESCRIPTION
M5709 is divided into RF block and Servo block. RF block consists of RF amp, attenuator, AGC(Auto Gain
Controller), Programmable equalizer/filter circuit. In RF block, the disc pit signal read from the optical pick-up
is input differentially into two RF signals for DVD(for CD, it is input into single RF signal)and the attenuator
adjusts the kind of disc and the difference of reflection and the AGC amplifies the signal in a fixed pattern and
it is input into programmable equalizer/filtter and in this section frequency range and phase of the RF signal is
adjusted and then sent to the output terminal.
RF Block Diagram
Servo block consists of Focus Error(FE), Tracking Error(TE), Center Error Detection circuit, Mirror, Defect
Detection circuit and Dual Auto Laser Power Controller(APC). On focus error and tracking error dection circuit,
the disc signal read from the optical pick-up is output to the signal with adjusted bias, gain, offset through the
operating process and on center error dection circuit, the error detection signal which protect the lense from
getting outside of center of track is come out. And while track jumping, it extracts the mirror signal to check the
number of crossing track by the signal generated when crossing between the tracks and on defect detection
circuit, the signal defect due to the foreign substances or scratch of the reflceted side of a disc can be
detected. Dual APC is the part which maintains the intensity of outcoming radiation from laser diode at a fixed
level to protect it from the change in level; if its intensity changes, there will be the problem in reading the RF
data.
a) Focus Block Diagram