User manual GRUNDIG P 37-730 TEXT SERVICE MANUAL

[. . . ] The regulations and safety instructions shall be valid as provided by the "Safety" Service Manual, part number 72010-800. The high tension for the picture tube and thus the developing Xradiation depends on the precise adjustment of the +A power supply. After every repair of the power supply unit or the horizontal deflection stage it is imperative that the EHT for the picture tube is checked and re-adjusted if necessary. To avoid consequential damages to the chassis or the picture tube the integrated protective circuits are allowed to be put out of operation only for a short time. [. . . ] After switching on, the processor (IC850) transfers the operating data from the internal memory via the I2C-bus to the bus-controlled modules and circuits. By evaluating the different voltage levels, the processor IC850-(27), -(28) knows which button on the keyboard has been pressed. 6 On Screen Display (OSD) For displaying data on the screen, the switching voltage "UData" IC850-(21) supplies a "High" level and blanks the picture tube by CT2832, IC150-(21) 4V . The character generator feeds out the display data via the output ports 16, 17, 18 of the microprocessor at an amplitude of 3. 7 Protection Circuit USchutz The base of the transistor T511 is connected via R511 to the low-end point of the vertical output stage, and via R512, D512, D513 to the reference pulse F from the horizontal output stage. 6V and higher switches the transistor on; via its collector the transistor switches IC850-(22) to ground. If the voltage +D fails there is no direct voltage present at the output of the vertical output stage IC400-(5) and consequently the proctection circuit input IC850-(22) is pulled to ground. When the Zener voltage is exceeded due to too high a beam current the collector voltage decreases to 0V so that the TV switches to standby. 1 Overview: With this TV design the whole signal processing is carried out in a single IC, i. In another path, the demodulated and controlled AF signal is present at IC150-(50) and is fed to the AF-IC TDA 7233. the luminance signal passes though the colour trap integrated in the IC. The delay line provided in the IC is used to correct delay time differences between the luminance and chrominance signal. The colour transient improvement (peaking) which follows is also realized in this IC. From this chroma signal, the burst is separated which is used to synchronise the colour oscillator in phase and frequency. By means of the colour carrier, the colour component signals are then demodulated and leave IC150 as R-Y and B-Y signals at Pin 30 and Pin 31 respectively. Following the PAL delay at CIC105 TDA 4665 the two signals, B-Y and R-Y, are fed back to IC150-(28), -(29) TDA 8362 A where they are clamped. In the matrix, the RGB signals are produced from the amplified signals and the Y-component. When the IC110 identifies the SECAM standard, from the chroma signal at pin 16, a current source at pin 1 is activated and sends a SECAM identification to IC150-(32). As soon as IC 150 too has identified SECAM, this IC sets pin 32 to 5V (1. This direct voltage is superimposed either by a regular clock frequency on PAL, or by bursts at a frequency of 4. The IC110 interprets these as an acknowledgement and switches the difference signal outputs R-Y and B-Y (pins 9 and 10) to 3. The difference signal outputs of IC150-(30), -(31) are thus The difference signals are returned to IC150 via the delay line CIC105. [. . . ] For this, a feedback signal from IC400 is present at IC150-(42) for negative feedback. 17 Non-Interlace Compensation with Teletext (25Hz Modulation) When a teletext (videotext) signal is displayed on the screen, the teletext signal would continuously change by one line upwards and downwards (non-interlaced teletext signal). to avoid the signal changing the line , the teletext IC2810-(13) supplies a 25Hz switching signal to IC150-(43). From this U25Hz switching voltage, a small DC voltage offset is derived for the deflection saw-tooth. [. . . ]