Hitachi C28W440N, Service Manual

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1. INTRODUCTION
This is a
110° chassis capable of driving 28-29”,32”,33” tubes at appropriate currents. The chassis have,
Frequency Controlled Tuning (PLL), and control system for multi-standard
(Pal,Secam,BG,DK,L/L’,I/I’,NTSC,M,N ) TV receivers with on-screen-display (OSD) for all relevant
control functions. The system is based on the ‘one-chip’ I
2
C bus controlled video processing/deflection
IC TDA8885 which also controls sound.
German stereo and Nicam is detected and processed by the MSP 3410 G. Dolby sound is processed by
MSP 3452 G, virtual dolby by MSP 3411G, BTSC Stereo by MSP 3420G (or MSP 3440G ) IC’s by
option. All sound processors also control the sound volume, balance, tone and spatial stereo effect.
The user-interface is menu based control system with cursor keys. Only for some functions the colour
keys are needed: This means that some of the functions can also be operated from the local keyboard
(i.e. Vol -, Vol +, P -, P+ and Menu).
Teletext is done by the microcontroller on-chip teletext module.Fastext/Toptext(8page),One page are
optional.
2. SMALL SIGNAL PART WITH TDA8885
The TDA8885 combines all small signal functions required for a colour TV receiver.
2.1.
Vision IF amplifier
The IF-amplifier contains 3 ac-coupled control stages with a total gain control range, which is higher
then 66 dB. The sensitivity of the circuit is comparable. The video signal is demodulated by means of
an alignment-free PLL carrier regenerator with an internal VCO. This VCO is calibrated by means of a
digital control circuit, which uses the clock frequency of the m-Controller/Teletext decoder as a
reference. The frequency setting for the various standards (33.4, 33.9, 38, 38.9, 45.75 and 58.75 MHz)
is realised via the I²C-bus. To get a good performance for phase modulated carrier signals the control
speed of the PLL can be increased by means of the FFI bit. The AFC output is generated by the digital