Low Voltage Protection, Gate Protector | Toshiba TW40F80 guide

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

Toshiba TW40F80 manual Low Voltage Protection, Gate Protector

Contents

TW40F80 Contents Terminal FUNCTION, Description and Block Diagram Wide Aspect Conversion Circuit Failure Analysis Section X Deflection Distortion Correction Circuit Section XI Digital Convergence Circuit Outline Merits of BUS System Section FeatureImproved Serviceability Reduction of Parts Count Specifications Chassis Model Front View Video 3 Inputs Rear View IN-VIDEO Remote Control View 100 Chassis Layout Starsight Newosd FRO. Surr Construction of Chassis Outline Major FeaturesSection II TUNER, IF/MTS/S. PRO Module Circuit Block RF AGC Audio Multiplex Demodulation Circuit A.PRO block diagram A.PRO Section Audio Processor Configuration of the audio circuit and signal flow are given POP Tuner Terminal No Name Operation of Channel Selection Circuit Microcomputer SDA SCL Microcomputer Terminal Function Microcomputer Terminal Name and Operation Logic Terminal Name Function In/Out Logic Remarks SDA On Screen FunctionEEPROMQA02 System Block Diagram Local KEY Detection Method Local key assignment Function To 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 HEX Service Adjustment Entering to Service ModeTest Signal Selection Executing Self Diagnosis Function Failure Diagnosis ProcedureContents to be Confirmed by Customer Understanding Self Diagnosis Indication Self Check Clearing method of self diagnosis result YES Troubleshooting ChartTV does Not Turned on No Acception of KEY-IN No Picture Snow Noise Memory Circuit Check No Indication On Screen Section IV DVD Switch Circuit DVD Switch Block Diagram Outline Circuit Operation ConfigurationSection V WAC Circuit Outline Operation Wide aspect conversion unit block diagram PB6348 Pin Function Pin function of TC9097F QFP 80 pin Names and functions of TC9097F Name Function VFL2 Block Diagram TC9097F system block diagram Wide Aspect Conversion Circuit Failure Analysis Procedures E2PROM OK? Adjustment Method Raster Horizontal One Screen 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 section Main/Sub Screen Superimposing Section Main/Sub screen superimposing section QY01 Main IC Terminal FUNCTION, Description and Block DiagramDiagram MPC1832GT QY01 mPC1832GT pin layout QY03 TC9092AF internal block diagram QY03 TC9092AF pin layout QY03 TC9092AF pin list No Pin name Pin function CKW MRD1 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 Operation Sawtooth Waveform Generation Output CircuitActual Circuit Circuit Operation Output 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 Balance UZ22BSD +35V Over Current Protection CircuitTheory of Operation UZ11BSB Raster Position Switching Circuit Ketsu Horizontal 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 FBT T3~t4 Description of the basic circuit T1~t2T2~t3 T4~t6 Curve Correction S Capacitor Amplitude CorrectionLinearity Correction LIN Left-right Asymmetrical Correction LIN coil Linearity coil Operation Theory White Peak Bending Correction CircuitOutline EHT Blanking Low Voltage Protection Gate Protector ABL High Voltage Generation CircuitAFC High Voltage DPC Circuit Regulator High Voltage 1. +210V2. +35V Anode High Voltage CircuitCR-BLOCK ED’ ActualFBT CR-BLOCK E H RAY Protection Circuit 23 X-RAY protection circuit Over Current Protection Circuit Functions and Features Block Diagram Diode Modulator Circuit OUT Actual 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 PLL Picture Adjustment Service Mode Entering/Exiting Mode Sfull Initial screenFirst screen Second screen Key function of remote control unit ENT Normal/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