TOSHIBA 20VL56B
Service Manual

1. Video Controller Unit & Display Data Conversion Unit The video controller unit receives the video signals inputted through the tuner, AV port (VIDEO1, VIDEO2, VIDEO3), and converts them into an ITU656 signal through the microcomputer (VCTI) combined with the video decoder that integrates various functions in one chip. Either component YPbPr signal or PC RGB signal is selected by the switching IC and inputted to a scaler (GM2221), which is sent to the LCD module after being modified to an LVDS signal through the integrated LVDS IC.(Only 15VL56B) Or, it is sent to the LCD module as a TTL output.(Only 20VL56B/G) VCTi is the main microprocessor that handles video signal processing and sound signal processing. It also manages the RF signals received from the tuner. The scaler can control timing to fit into the LCD panel, and can also control the size and position of the input signal. 2. Power Supply Unit The power supply unit provides 15V and 5V DC power to the mainboard. The PWM Step- Up DC/ DC Converter circuit is used to generate the 33V used for the tuner. 15V power is directly used by the sound amplifier IC and is also used to generate 5V and 3.3V power through the Step- Down DC/ DC Converter. 5V power is converted to 3.3V and 1.8V power through the regulator, which in turn supplies electrical power for ICs such as VCTI and scaler.

* The information contained in this section subjects to model.

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