Technology of Q 2500 colour TV set

Technology of Q 2500 colour TV setTo compensate for this a rotation panel (rastercorrection) is incorporated into the 81 cm devicewith chassis Q 2500. As the effect on theraster is less on smaller and 4:3 tubes therotation panel is not required.For the raster correction a circular coil is attachedto the cone of the c.r.t. If a uniformcurrent flows through it, the electron beamrotates around its own axis. As the createdmagnetic field overlays the field of the deflectioncoils, the picture can be rotated about itscentral point.2.10.2 CircuitFor raster correction the DAC on pin 25 of thevideo/deflection processor TDA 9332 is used.The voltage produced can be adjusted by theuser via “rotate picture“ and in service mode.It flows via W 1021, pin 3 to the rotation panelW 1, pin 3.R16U12ROTW01123R21R23R11C16C30C23R12C11C17I 01C10+89-C01R36Q26Q28C27 C472 1W31R38 R41R42Q47Q48I 01A+1-C0232C31C124I 0111R39In this way the inverting input of the operationalamplifier on pin 9 of I1C is controlled onthe rotation panel. At maximum anticlockwiserotation approximately 3.2 V is applied and atmaximum clockwise rotation 3.3 V. The operationalpoint is adjusted on pin 10 by R21 andR23. According to the voltage difference betweenpin 10 and pin 9 the push-pull stageQ26 and Q28 is controlled. On the base connectionsthere is a voltage of 0.6 to 10.6 V.The output voltage of the push-pull stage isapplied to pin 2 of the correction coil and atthe same time is fed to the inverting input ofoperational amplifier I1A via R 38 and R41.This also controls the second push-pull stageQ 48/Q 47. The two OPVs and push-pullstages counteract each other. This means thata current can flow to earth via Q 26, throughthe correction coil (from pin 2 to pin 1 on W31)and via Q48. On pin 8 of the OPV there is avoltage of 10.6V at maximum clockwise rotationand on the other output pin 1, 0.6 V. Otherwisethe current flows via Q 47 through thecorrection coil (in this case from pin 1 to pin 2on W 31) and via Q28 to earth.In this way the current can be adapted to therequired correction with respect to directionand size. This correction can, however, alsoact in reverse, if the coil is rotated on the deflector.The control electronics for the rotation coil isfixed firmly to the Q 2500 chassis. However,the rotation coil and control electronics shouldbe considered as a unit. In the event of a faultthe coil is then changed as a complete unit.Document Q 2500 41 © Loewe ProCollege