Technology of Q 2500 colour TV set

Technology of Q 2500 colour TV setThis reset reaches MSP 3410 /pin 21, and thetwo VCP 3230/33 /pin 15.All other IC’s either do not need a reset orgenerate it on switching on the operating voltage.4.1.5 Creation of cycle frequencyThe internal oscillator of SDA 6000 is synchronisedwith a 6 MHz quarz on pins 108 and109. The cycle frequency for the bus systemsis obtained from this frequency by internaldistribution. They are from 70 to 400 kHz respectivelyfor the I²C bus systems. The cyclefrequency is transferred under software controldepending on the current function.4.1.6 Operational commandsThe SDA 6000 receives operational commandsas serial data information by RSIGsignal on pin 9. The local operating commandsare applied to the CCU on pin 126 asvarious voltage values.Pin 126 operates as an ADC with 6 bit resolution.By various voltage dividers on the threeoperating unit buttons, various voltage levelsare produced.The voltage levels are digitised by the ADC,and based on the measured values the CCUissues the appropriate commands.The following voltages are produced by manipulationof the various buttons:•• “+“ button- 0.5 V• “-“ button- 1.1 V• “ “ button - 1.8VThe overtravel contact is connected to pin 93of the CCU.4.1.7 LED displayThe red standby LED is controlled via pin 96of the CCU. In operation the remote controlcommands in RC5 code are acknowledged bytransient illumination of the LED. For standbyoperation the pin is set to the H level andtransistor Q 2853 thereby conducts, whereuponthe LED illuminates. The ON LED iscontrolled via pin 78 with the ON/OFFcommand.When the power supply is switchedon this line is set to the L level, whereby thegreen ON LED also illuminates. SAT standbyoperation is indicated by illumination of thetwo LED’s.4.1.8 ON/OFF functionIf a switch-on command is present, the outputON/OFF, pin 78 of the CCU is set to L level.This blocks transistor Q 8111 in the standbypower supply, whereupon Q 8114 conductsand attracts the relay. The system voltage isable to reach the main power supply, whichbegins to operate.The device starts operating at the selectedprogram location. The output is once again setto H level by an off command.With an ON/OFF command the two transistorsQ 2961 and Q 2966, which form part of themute circuit, are switched, thus suppressinginput and output noises.4.1.9 Protective circuitIn order to avoid excessive high voltage, c.r.t.defects or other serious damage due to faultsin the vertical deflection, caused by excessivebeam current, the device is switched tostandby. In addition, pin 94 of the CCU is setto H level. In normal operation L level is present(see description basic board Section 5.2– 6.2).Document Q 2500 68 © Loewe ProCollege