Technology of Q 2500 colour TV set

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Technology of Q 2500 colour TV setHalfpic. A.Halfpic. B50HzSampling rate13.5 MHz.100 Hz principleHalfpicturememory,3.5 MbitHalfpic. A.Halfpic. A100Hz.Halfpic. BSampling rate 27 MHz.Halfpic. B.The following integrated modules are responsiblefor colour saturation, brightness and contrastsetting. Control is via the I²C bus fromthe CCU. The same is true for the white andblack value setting. An automatic black valuesetting is also available. With this cutoff control,signs of ageing, e.g. the c.r.t, are corrected(see description of the RGB outputstages).In the Y signal path there is a peaking circuit.It is used to produce black/white edges onovershoots, which increases the sharpness ofthe picture. The height of the overshoot canbe adjusted with the "Sharpness" operatingfunction.With three output side DACs analogue Y-, R-Y- and B-Y- signals are produced, which arethen output on pins 44, 46 and 48.Finally the Y- and colour difference signals arefed through low-pass filters to filter out interferencepulses and the residue of digitisation.The last IC is the TDA 9332 for the 100 Hzcolour signal processing. It controls the RGBpower output stages to the c.r.t plate.The Y-, R-Y- and B-Y signals output on pins26, 27 and 28 produce RGB signals usinganalogue matrix circuits.The IC carries out further processing of analogueRGB signals (twice), CCU signals(once) and signals from the optional VGA interfaceor online module. Depending on theassociated blank information, both the internallyproduced and the two RGB signals froma selection circuit are switched.The signals reach pins 40, 41 and 42 via theRGB output amplifier and are held there at 4Vss for control of the speed modulator and theRGB output stages.4.2.15 IC functionsThe following paragraphs give a more detaileddescription of the functions of the ICs used forpicture processing.In the descriptions, the processes are shownin a much-simplified form. The operationsnecessary for the execution of the functionsare inevitably much more complex.4.3 VPC 3230Video processorThe VPC 3230 is a recently developed videoprocessor from Intermetall in 0.8 µ CMOStechnology.The functions are contained in an80 pin PLCC housing.Document Q 2500 84 © Loewe ProCollege
Technology of Q 2500 colour TV setVPC 3230 block diagramAV2AV3DVBChroma73CVBS/YAV3/Synch74auf YH-SynchVGA72751BG2R 3FB29U/B45Y/GV/R 6InputinterfaceAGC2 x ADCRGB/YUVInputinterface4 x ADCY/GU/BV/RFB4 linecombfilterNTSCPALRGB/YUV - InterfaceMatrixMultistandardcolourdecoderNTSCPALSECAMYCrCbFBYCrCbMixerYCrCbLinecompress./decompress.LetterboxdetectorI 2 C BusClockGen.I 2271VPC 3230OutputFormatterMemoryControlSynch+ClockGeneration83285457LM0-7FIFOCNTLLL ClockH SynchV Synch62 63 1720.25 MHzI 2 C BusV SynchVGAThe functions in the VPC 3230 can be roughlysummarised into 9 blocks:- Input interface with signal selectionand two precision 8 bit A/D converters- 20.25 MHz clock generator- high quality, adaptive 4 linecomb filter- Multistandard colour decoder for PAL,NTSC and SECAM- Letterbox detector- Output format conversion(Output formatter)- I²C bus interface- Synchronisation block4.3.1 Input interfaceOn signal board Q 2500, the input multiplexeris switched in such a way that a choice can bemade between two pairs of signals. If anFBAS signal, for example, is supplied by areceiver unit or a Y/C signal is fed to an interface,pin 73 for the FBAS/Y signal and pin 72for the chroma signal are switched.So that the signals from the ADC can be correctlydigitised, two conditions must be fulfilled.The d.c. level and the amplitude of thesignals must be adapted to the ADC . The d.c.level is defined by a signal clamp. For thisthere is a clamp circuit in the FBAS/Y paththat clamps the signal to the rear black shoulder.- RGB/YUV interfaceDocument Q 2500 85 © Loewe ProCollege
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