Technology of Q 2500 colour TV set

Technology of Q 2500 colour TV setIn these devices the V output stage ofSTV9379FA is used. For the flyback generatorthis has an independent voltage supply. AUSVM/60V is used that is fed to the I 561 viathe fused resistor R 559 on pin 3.If the V output stage is changed during servicethen ensure it is replaced with the same type.The two IC variants are not compatible.2.6.2 Vertical protection circuitsProtection circuits are used to protect the c.r.t.against burning if the vertical deflection fails.For a d.c. coupled V output stage a fault situationcan theoretically occur in which the deflectionsaw tooth appears to be available, buta faulty d.c. component directs the electronbeam to the upper or lower end of the c.r.t.neck. This could cause the c.r.t. neck to meltand lead to destruction of the c.r.t. neck.To prevent this a V saw tooth is taken fromthe base of the V deflection coils with R 573and a d.c. voltage is applied to the signalboard with R 2651.U40V13VVertical protective circuit via CCUtBasic boardC563C564R563W1731Pin 4R1036Signal boardU5R2594D2594I 2801CCU/Pin94D2661D2586UV+D56126 3FlybackGeneratorD2591D1769R2593C2592/93R2594Q2594R2586UV-4I 561TDA 8177Bild 2 - 15This VPROT signal is fed to the protectivecircuit that consists of the dual operationalamplifier I 2651. Operational amplifier A workson its non-inverting input pin 3, with referencevoltage of 3 V and operational amplifier B onits inverting input pin 6 with 5 V. If the VPROTsignal - Diagram A – does not fall below orexceed the reference values of 3V and 5 V,then the V deflection and the vertical d.c.component through the deflection coils is correct.If the d.c. component is too positive ortoo negative - Diagrams B + C – this is interpretedas a fault. If, for example, the d.c.component of the VPROT signal is too small(5V DiagramB ) pin 7 goes from OP B to H level andthe CCU switches the device off.Document Q 2500 30 © Loewe ProCollege