Toshiba TW40F80 Protection Circuit for V Deflection Stop, Linearity Characteristic Correction

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2-4. V Linearity Characteristic Correction

2-4-1. S-character Correction

(Up-and Down-ward Extension Correction)

A parabola component developed across C306 is integrated by R306 and C305, and the voltage is applied to pin 6 of Q302 to perform S-character correction.

2-4-2. Up-and Down-ward Linearity Balance

A voltage developed at pin 2 of Q301 is divided with resistors R307 and R303, and the voltage is applied to pin 6 of Q301 to improve the linearity balance characteristic.

3. PROTECTION CIRCUIT FOR V DEFLECTION STOP

Q301

2

L462+L463+L464

C306

Q350

	R352	12V 9V
D350		12V 9V
D350
R351		R354
	Q351		BLANKING
C350	Q351	D354	CIRCUIT
		D354

R305

R350

Q353

D353

Fig. 8-9

When the deflection current is not supplied to the deflection coils, one horizontal line appears on the screen. If this condition is not continued for a long time, no trouble will occur in a conventional TV. But in the projection TV, all the electron beams are directly concentrated at the fluorescent screen because of no shadow mask used, and burns out the screen instantly.

To prevent this, the stop of the V deflection is detected when the horizontal one line occurs, and the video signals are blanked out so that the electron beams are not emitted.

When the V deflection circuit is operating normally, a sawtooth wave voltage is obtained across (R305), so Q350 repeats on-off operation in cycle of V sync. In this case, the collector voltage of Q35 is set to develop less than (12V- VBE (Q351)) with R352 and C350 as shown in Fig. 8-9. Accordingly, Q351 and Q353 are continuously turned on. As a result, diode D354 is turned off, giving no influence on the blanking operation.

Next, when the V deflection stops, the voltage across (R305) does not develop, so Q350 turns off, and both the Q351 and Q353 are turned off. Then, the picture blanking terminal pin 13 of ICA05 is set to high through R354 and D354 connected to 90V power line, BLANKING CIRCUIT ON thus cutting off the projection tubes.

Volttage Across

R305

Q350 BASE

Q340 VBE

12V-VBE(Q341)

Q351 Collector

Fig. 8-10

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Image 63

Contents TW40F80 Contents Wide Aspect Conversion Circuit Failure Analysis Terminal FUNCTION, Description and Block DiagramSection XI Digital Convergence Circuit Section X Deflection Distortion Correction CircuitReduction of Parts Count Section FeatureImproved Serviceability Outline Merits of BUS SystemChassis Model SpecificationsVideo 3 Inputs Front ViewIN-VIDEO Rear View100 Remote Control ViewStarsight Newosd FRO. Surr Chassis LayoutConstruction of Chassis RF AGC Major FeaturesSection II TUNER, IF/MTS/S. PRO Module Circuit Block OutlineAudio Multiplex Demodulation Circuit A.PRO Section Audio Processor A.PRO block diagramConfiguration of the audio circuit and signal flow are given Terminal No Name POP TunerOperation of Channel Selection Circuit SDA SCL MicrocomputerMicrocomputer Terminal Function Terminal Name Function In/Out Logic Remarks Microcomputer Terminal Name and Operation LogicOn Screen Function EEPROMQA02SDA System Block Diagram Local key assignment Function Local KEY Detection MethodRemote Control Code Assignment Code FunctionTo TV set Custom codes are 40-BFH TV set for North U.S.A Code Function OPT0 OPT1 Models HEX Optional Setting for Each ModelEntering to Service Mode Test Signal SelectionService Adjustment Failure Diagnosis Procedure Contents to be Confirmed by CustomerExecuting Self Diagnosis Function Self Check Understanding Self Diagnosis IndicationClearing method of self diagnosis result Troubleshooting Chart TV does Not Turned onYES No Picture Snow Noise No Acception of KEY-INNo Indication On Screen Memory Circuit CheckSection IV DVD Switch Circuit DVD Switch Block Diagram Outline Operation ConfigurationSection V WAC Circuit Outline Circuit OperationWide aspect conversion unit block diagram PB6348 Pin function of TC9097F QFP 80 pin Pin FunctionName Function Names and functions of TC9097FVFL2 TC9097F system block diagram Block DiagramE2PROM OK? Wide Aspect Conversion Circuit Failure Analysis ProceduresRaster Horizontal One Adjustment MethodSection VI Dual Circuit Outline Principles of OperationScreen multi-search process System Component Diagram of Dual Unit Video/Color/Deflection Process Section OSD Sub screen process section Sub Screen Process SectionMain/Sub screen superimposing section Main/Sub Screen Superimposing SectionMPC1832GT Main IC Terminal FUNCTION, Description and Block DiagramDiagram QY01QY01 mPC1832GT pin layout QY03 TC9092AF internal block diagram QY03 TC9092AF pin layout CKW QY03 TC9092AF pin list No Pin name Pin functionMRD1 QY10/QY11 M518221-30ZS internal block diagram Section VII 3-DIMENSION Y/C Separator Circuit Outline Configuration Circuit DescriptionCircuit Description Terminal description PZ01 Theory of Operation Section Viii Vertical Output Circuit OutlineCircuit Operation Output CircuitActual Circuit Sawtooth Waveform GenerationOutput Output stage power supply voltage Up-and Down-ward Linearity Balance Linearity Characteristic CorrectionProtection Circuit for V Deflection Stop Character Correction Up-and Down-ward Extension CorrectionUZ11BSB +35V Over Current Protection CircuitTheory of Operation UZ22BSDKetsu Raster Position Switching CircuitBasic Operation of Horizontal Drive SignalSection IX Horizontal Deflection Circuit Outline Horizontal Drive CircuitOn period OFF period FBT Signal DEF/POWER PCBHorizontal Output Circuit Operation of Basic CircuitT4~t6 Description of the basic circuit T1~t2T2~t3 T3~t4Amplitude Correction Linearity Correction LINCurve Correction S Capacitor Linearity coil Left-right Asymmetrical Correction LIN coilEHT White Peak Bending Correction CircuitOutline Operation TheoryBlanking Gate Protector Low Voltage ProtectionHigh Voltage DPC Circuit Regulator High Voltage Generation CircuitAFC ABL1. +210V 2. +35VHigh Voltage High Voltage Circuit CR-BLOCKAnode Actual FBT CR-BLOCK E HED’ 23 X-RAY protection circuit RAY Protection CircuitOver Current Protection Circuit Block Diagram Functions and FeaturesOUT Diode Modulator CircuitActual Circuit Basic Operation and Current Path Later Half Scanning PeriodFirst Half Scanning Period Later Half of Flyback Period First Half of Scanning PeriodP.T Section XI Digital Convergence Circuit Outline PLL ResetMemory PromPicture Adjustment Entering/Exiting Mode Service ModeInitial screen First screen Second screenSfull ENT Key function of remote control unitOperation procedure Each Screen Adjustment MethodNormal/Full Theater Wide1 Theater Wide 269.5 When CRT is Replaced When Convergence Unit is ReplacedCase Study Troubleshooting Adjusting Procedure in Replacing CRTAdjusting Procedure in Replacing Convergence Unit/Main Def Convergence Output Circuit Convergence Block Diagram Convergence Troubleshooting Chart Main Unit