Toshiba TW40F80 manual Low Voltage Protection, Gate Protector

Page 74

4-4. 200V Low Voltage Protection

4-4-1. Outline

When the video output power supply 200V is stopped by some abnormality occurence, the current inside CPT in- creases abnormally. So the CPT may be damaged. To pre- vents this, a 200V low voltage protection circuit is provided.

4-4-2. Theory of Operation

Fig. 9-14 shows a connection diagram.

Under a normal condition Q340 is always on because of about 210V supplied from the 200V line. Accordingly Q340 col- lector is kept at about 6.2V or the zener voltage of D341 and Q341 is turned off.

If some abnormality occurs and 200V line voltage lowers by less than about 160V. Q340 turns off and its collector voltage rises. So Q341 turns on. With Q341 turned on the voltage at pin 14 of Z801 (expander) exceeds a threshold voltage and pin 16 of Z80 is high level and makes the power relay turn off.

CRT-D Circuit

200V 1

2

Deflection circuit

P405P301

1	R436

2 8

17

R879

Z801

14 GATE PROTECTOR

16

C894

	DPC circuit			-12V
				-12V
	R389		R390
	P350
	Q340
8				Q341
				Q341
17	D340
	R391
		D341	R392	C340
	D315	R346

Fig. 9-14

74

Image 74

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 RemarksSDA On Screen FunctionEEPROMQA02 System Block Diagram Local KEY Detection Method Local key assignment FunctionTo TV set Remote Control Code AssignmentCode Function Custom codes are 40-BFH TV set for North U.S.A Code Function Optional Setting for Each Model OPT0 OPT1 Models HEXService Adjustment Entering to Service ModeTest Signal Selection Executing Self Diagnosis Function Failure Diagnosis ProcedureContents to be Confirmed by Customer Understanding Self Diagnosis Indication Self CheckClearing method of self diagnosis result YES Troubleshooting ChartTV does Not Turned on 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 OneScreen multi-search process Section VI Dual Circuit OutlinePrinciples of Operation 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 Circuit Description Section VII 3-DIMENSION Y/C Separator Circuit OutlineConfiguration Circuit 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 DriveOn period OFF period Operation of Basic Circuit Signal DEF/POWER PCBHorizontal Output Circuit FBTT3~t4 Description of the basic circuit T1~t2T2~t3 T4~t6Curve Correction S Capacitor Amplitude CorrectionLinearity Correction LIN 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 RegulatorHigh Voltage 1. +210V2. +35V Anode High Voltage CircuitCR-BLOCK ED’ ActualFBT CR-BLOCK E H RAY Protection Circuit 23 X-RAY protection circuitOver Current Protection Circuit Functions and Features Block DiagramDiode Modulator Circuit OUTActual Circuit First Half Scanning Period Basic Operation and Current PathLater Half Scanning Period P.T Later Half of Flyback PeriodFirst Half of Scanning Period Section XI Digital Convergence Circuit Outline Prom ResetMemory PLLPicture Adjustment Service Mode Entering/Exiting ModeSfull Initial screenFirst screen Second screen Key function of remote control unit ENTNormal/Full Operation procedureEach Screen Adjustment Method Theater Wide1 Theater Wide 269.5 Case Study When CRT is ReplacedWhen Convergence Unit is Replaced Adjusting Procedure in Replacing Convergence Unit/Main Def TroubleshootingAdjusting Procedure in Replacing CRT Convergence Output Circuit Convergence Block Diagram Convergence Troubleshooting Chart Main Unit