User manual DAEWOO CP-490 SERVICE MANUAL

[. . . ] S/M No:CP490P-010 Colour Television CHASSIS : CP-490 MODEL : DTR-14D3VG DTR-14D3TM DTR-16D3VG DTR-20D3VG DTR-20D3TM DTR-21D3TMW DTR-21D3VGW DTR-21D3TGW DAEWOO ELECTRONICS CO. , LTD. CONTENTS Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Safety Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Circuit block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Alignment Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] · Pre-amplifier and mute The pre-amplifier output signal available at the deemphasis pin can be used for SCART application. At this pin the deemphasis capacitor has to be connected. The output level is 500m Vrms for a AM swing of 50kHz A pre-amplifier with DC feedback has been provided. The DC component of the deemphasis signal is always 3V, also during sound mute. When no video signal is identified the deemphasis output is automatically muted. · Audio switch Anaudio switch has been provided for full SCART function. The audio switch is controlled by the I2C bus Source Select INA/INC. for positive modulation, MOD, the external sound input is automatically selected for an external AM sound demodulator. · Volume controlled amplifier The volume control is active for both internal and external audio signals. The nominal gain is +9dB and minimal 71dB, which gives a total control range of 80dB minimal. In the Fixed Audio Volume mode, FAV, the deemphasis signal is fed directly to the sound output buffer. This feature is mainly for further stereo processing where a fixed audio level is required. This saves an external buffer at the deemphasis pin. · Automatic Volume Levelling (AVL) The Automatic Volume Levelling(AVL) circuit is an automatic gain control on the volume which regulates the audio level to a constant sound level with non-standard TV signals (i. e. The regulated output level can be adjusted by means of the volume control. The AVL function can be activated via I2C-bus and is available for the TDA8840/1/2/6/6A. By means of the external AVL capacitor the time constant can be chosen. The AVL circuit works properly for an AVL input signal range of approx. This is the so called "boost range" and is 20dB. Within the "boost range" any desired stabilised output level can be adjusted by means of the volume control. The characteristic is automatically adapted for selected crystals as 4. 43MHz (PAL) and 3. 57MHz(NTSC) standards by means of the 0/6dB attenuator controlled by the XA bit. An external AVL capacitor, connected to pin 45, acts as a "memory" capacitor and integrates the audio peak signal. [. . . ] In addition, even after the latch circuit start operating, the constant voltage regulator (Reg) circuit is in operation and the circuit current is at high level. As a result, VIN terminal voltage rapidiy decreases. When VIN terminal voltage become lower than the shutdown voltage, VIN(OFF), (4. 9V typical), it starts increasing as the circuit current is below 500µA. When it reaches the ON-state voltage, VIN(ON) (8V typical), Vin terminal voltage starts decreasing because the circuit current increases again. [. . . ]