Toshiba TW40F80 Amplitude Correction, Linearity Correction LIN, Curve Correction S Capacitor

Page 70

Amplitude Correction

To vary horizontal amplitude, it is necessary to vary a sawtooth wave current flowing into the deflection coil. These are two methods to vary the current; a method which varies LH by connecting a variable inductance L in series with the deflection yoke, and a method which varies power supply voltage (across S-character capacitor) for the deflection yoke.

As the DPC circuits is used in the this chassis, the later method which varies the deflection yoke power supply volt- age by modifying the bus data is used.

4-1-2. Linearity Correction (LIN)

t2	t1		t2	t1
θ2	θ1	t2 = t1	θ2	θ1	t2 > t1
		θ2 < θ1			θ2 = θ1

(a) S-character correction

(b)

Fig. 9-7

(1) S-curve Correction (S Capacitor)

Pictures are expanded at left and right ends of the screen

even if a sawtooth current with good linearity flows in

the deflection coil when deflection angle of a picture

tube increases. This is because projected image sizes

on the screen are different at screen center area and

the circumference area as shown in Fig. 9-7. To sup-

press this expansion at the screen circumference, it is

necessary to set the deflection angle q1 to a large value

(rapidly deflecting the electron beam) at the screen

center area, and to set the deflection angle q2 to a small

value (scanning the electron beam slowly) at the cir-

cumference area as shown in Fig. 9-7.

In the horizontal output circuit shown in Fig. 9-8, ca-

pacitor CS connected in series with the deflection coil

L is to block DC current. By properly selecting the

TR

Cs

D Co

Vcc

(a) H output circuit

LH

Deflection coil

H

value of CS and by generating a parabolic voltage de-

veloped by integrating the deflection coild current

across the S capacitor, and by varying the deflection

yoke voltage with the voltage, the scanning speed is

decreased at beginning and end of the scanning, and

increased at center area of the screen. The S curve cor-

rection is carried out in this way, thereby obtaining

pictures with good linearity.

(b) Sawtooth wave current

(c) Voltage across LH Fast deflection

Slow deflection

(d) Synthesized current

Fig. 9-8

70

Image 70

Contents TW40F80 Contents Terminal FUNCTION, Description and Block Diagram Wide Aspect Conversion Circuit Failure AnalysisSection X Deflection Distortion Correction Circuit Section XI Digital Convergence CircuitOutline Merits of BUS System Section FeatureImproved Serviceability Reduction of Parts CountSpecifications Chassis ModelFront View Video 3 InputsRear View IN-VIDEORemote Control View 100Chassis Layout Starsight Newosd FRO. SurrConstruction of Chassis Outline Major FeaturesSection II TUNER, IF/MTS/S. PRO Module Circuit Block RF AGCAudio Multiplex Demodulation Circuit A.PRO block diagram A.PRO Section Audio ProcessorConfiguration of the audio circuit and signal flow are given POP Tuner Terminal No NameOperation of Channel Selection Circuit Microcomputer SDA SCLMicrocomputer Terminal Function Microcomputer Terminal Name and Operation Logic Terminal Name Function In/Out Logic RemarksEEPROMQA02 On Screen FunctionSDA System Block Diagram Local KEY Detection Method Local key assignment FunctionCode Function Remote Control Code AssignmentTo TV set Custom codes are 40-BFH TV set for North U.S.A Code Function Optional Setting for Each Model OPT0 OPT1 Models HEXTest Signal Selection Entering to Service ModeService Adjustment Contents to be Confirmed by Customer Failure Diagnosis ProcedureExecuting Self Diagnosis Function Understanding Self Diagnosis Indication Self CheckClearing method of self diagnosis result TV does Not Turned on Troubleshooting ChartYES No Acception of KEY-IN No Picture Snow NoiseMemory Circuit Check No Indication On ScreenSection IV DVD Switch Circuit DVD Switch Block Diagram Outline Circuit Operation ConfigurationSection V WAC Circuit Outline OperationWide aspect conversion unit block diagram PB6348 Pin Function Pin function of TC9097F QFP 80 pinNames and functions of TC9097F Name FunctionVFL2 Block Diagram TC9097F system block diagramWide Aspect Conversion Circuit Failure Analysis Procedures E2PROM OK?Adjustment Method Raster Horizontal OnePrinciples of Operation Section VI Dual Circuit OutlineScreen 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 sectionQY01 Main IC Terminal FUNCTION, Description and Block DiagramDiagram MPC1832GTQY01 mPC1832GT pin layout QY03 TC9092AF internal block diagram QY03 TC9092AF pin layout QY03 TC9092AF pin list No Pin name Pin function CKWMRD1 QY10/QY11 M518221-30ZS internal block diagram Configuration Circuit Description Section VII 3-DIMENSION Y/C Separator Circuit OutlineCircuit Description Terminal description PZ01 Section Viii Vertical Output Circuit Outline Theory of OperationSawtooth Waveform Generation Output CircuitActual Circuit Circuit OperationOutput Output stage power supply voltage Character Correction Up-and Down-ward Extension Correction Linearity Characteristic CorrectionProtection Circuit for V Deflection Stop Up-and Down-ward Linearity BalanceUZ22BSD +35V Over Current Protection CircuitTheory of Operation UZ11BSBRaster Position Switching Circuit KetsuHorizontal Drive Circuit SignalSection IX Horizontal Deflection Circuit Outline Basic Operation of Horizontal Drive On period OFF period Operation of Basic Circuit Signal DEF/POWER PCBHorizontal Output Circuit FBTT3~t4 Description of the basic circuit T1~t2T2~t3 T4~t6Linearity Correction LIN Amplitude CorrectionCurve Correction S Capacitor Left-right Asymmetrical Correction LIN coil Linearity coilOperation Theory White Peak Bending Correction CircuitOutline EHTBlanking Low Voltage Protection Gate ProtectorABL High Voltage Generation CircuitAFC High Voltage DPC Circuit Regulator2. +35V 1. +210VHigh Voltage CR-BLOCK High Voltage CircuitAnode FBT CR-BLOCK E H ActualED’ RAY Protection Circuit 23 X-RAY protection circuitOver Current Protection Circuit Functions and Features Block DiagramDiode Modulator Circuit OUTActual Circuit Later Half Scanning Period Basic Operation and Current PathFirst Half Scanning Period First Half of Scanning Period Later Half of Flyback PeriodP.T Section XI Digital Convergence Circuit Outline Prom ResetMemory PLLPicture Adjustment Service Mode Entering/Exiting ModeFirst screen Second screen Initial screenSfull Key function of remote control unit ENTEach Screen Adjustment Method Operation procedureNormal/Full Theater Wide1 Theater Wide 269.5 When Convergence Unit is Replaced When CRT is ReplacedCase Study Adjusting Procedure in Replacing CRT TroubleshootingAdjusting Procedure in Replacing Convergence Unit/Main Def Convergence Output Circuit Convergence Block Diagram Convergence Troubleshooting Chart Main Unit