Technology of Q 2500 colour TV set

Technology of Q 2500 colour TV setLM = Leakage current measurementCut - off measurementMRMGMBCut - off measurement pulseLMMRLMMGR - ChannelG - ChannelLMMBB - ChannelThis means that the traditional adjustmentcontroller and the associated adjustment workis no longer required.Directly after the vertical picture return, measurementsare taken of the leakage current ofthe c.r.t. systems at ultra blank and then, oneafter the other, the cathode currents of thethree systems after input of a specific blankvalue.These pulses are fed with the respective RGBsignals via the output stages of the c.r.t. systems.From the output stage IC's the respectiveblank currents of the control circuit invideo IC I 2521 on the signal board are suppliedvia its pin 44.From a comparison between the establishedblank current and a reference value, whichrepresents the specified current, a differenceis obtained, which controls the cathode currentvia the video output stages as a controlleroutput. It is dynamically stabilised just abovec.r.t. blocking current, up to control tolerances.As small leakage currents in the output stagesof the c.r.t.s could lead to distortion of the cutoff control, measurement of the leakage currentis carried out during the vertical flybackbefore measurement of the three blankingcurrents.35TDA 9332Cut - off circuit principle36 37RGBInsertion38White PointandBrightnessControlBeamCurrentLimterC2534Fromcathoderay tubePCB43A consequence of a change to the UG2-voltage is that the cut off control opposes thischange. Only a transient effect can be detectedon the screen, as long as the control3429OutputAmplifierandBufferContinuousCathodeCalibration404142RGBW1051Cut off44BCLDocument Q 2500 39 © Loewe ProCollege