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Toshiba MM20E45, Техническое учебное пособие

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10-2

2. X-RAY PROTECTION CIRCUIT–1

In the CPT using a high voltage, if an excessive high voltage
occurs due to abnormal operation of a circuit, X-ray may be
caused. So, a X-ray protection circuit is provided.

Fig. 2 shows the X-ray protection circuit. In operation, if
chopper regulator QH24 is shorted due to some reasons, the
resonant pulse being developed at pin 

 of FBT will

increase  and a high voltage will be higher. At the same time,
the pulse at pin 

 of the FBT also increases. As a result, a

X-ray  protection  circuit detection voltage (ED) rectified
with D471 and C471 increases.

With the ED increased and emitter voltage of Q471 (which
is divided by R463, R465) exceeds D472 zener voltage
(6.2V) + Q471 V

BE

 (0.7V), Q471 turns on and a base current

flows into Q472.

Then, Q472 turns on and a gate voltage is applied to a
thyrister D862. The thyrister D862 turns on and drops base
voltage of Q863 which is driving a relay to zero, so, the relay
is cut off. Since the thylister D862 is connected to the standby
5V line, D862 continues  to on until the main power source
is off. A series of operations shown above is conducted for
an instant time period. The Q471 is set to be not turned on
under normal condition.

Fig. 2

X-ray protection circuit–1

R461

D471

5

FBT

4

C471

R476

Q471

R465

12V

Q472

R431

D473 R432

C474

R464

D472

C867

D862

R875 Q863

Q862

R877

Relay

ICA01 Pin 1

Содержание MM20E45

Страница 1: ...COLOUR TELEVISION MM20E45 TECHNICAL TRAINING MANUAL FILE NO 016 9502 N5MM1 Chassis ...

Страница 2: ...YNC SIGNAL PROCESSING CIRCUIT SECTION VI SYNC SEPARATION CIRCUIT OF TV MODE SECTION VII HORIZONTAL AND VERTICAL OSCILLATION CIRCUIT SECTION VIII VERTICAL DEFLECTION CIRCUIT SECTION IX HORIZONTAL DEFLECTION CIRCUIT SECTION X PROTECTION CIRCUIT SECTION XI OSD STABILIZATION CIRCUIT SECTION XII PICTURE TUBE SECTION XIII POWER SUPPLY CIRCUIT SECTION XIV FAILURE DIAGNOSIS PROCEDURES ...

Страница 3: ...Television reception a monitor running Multimedia PC applications or for playback of video games The 20 FST picture tube features a stripe pitch 0 58mm providing a favourable comparisonstoconventionaldesignswhichgenerallymeasure 0 75 to 0 9mm 2 PC BOARD CONFIGURATION 1 Power V C D PB5226 PB5226 1 Power PB5226 2 V C D 2 Deflection PB5227 3 Signal Video PB5228 PB5228 1 Signal PB5228 2 Video PB5228 3...

Страница 4: ...ans Stand by trans Sound out radiator V out radiator Choke coils Choke trnas H out radiator Signal unit Jack board S VIDEO Tuner Video unit D sub unit D sub connector Front keys Power LED Remote control receiver Flyback trans Def unit V C D unit Rectifier Power radiator ...

Страница 5: ...1 3 4 LOCATION OF CONTROLS 4 1 TV Set RGB TV VIDEO button MENU button ADV button VOLUME CHANNEL POWER indicator REMOTE senser POWER button ...

Страница 6: ...cate locations on your TV set They can be controlled only by the Remote Control Aim at the TV set TIMER button Channel Number buttons CH RTN Channel Return button MTS button POWER button MUTE button SET UP button buttons OPTION button RESET button PIC Picture button TV VIDEO button RECALL button AUD Audio button CHANNEL buttons VOLUME buttons ...

Страница 7: ...ter RGB AUDIO INPUT Jacks provide for direct connection of a personal computer with audio output terminals S VIDEO INPUT Jack provide for direct S video connection from an S VHS VCR or a video disc player VIDEO AUDIO INPUT Jacks provide for direct connection of video devices VCR video disc player camcorder etc with video audio outputs VARIABLE AUDIO OUTPUT Jacks feed volume controlled stereo audio...

Страница 8: ...ion LA7860 S shape capacitor switching Linear coil switching Resonance capacitor switching Drive switching Synchronizing signal switching TC40538P F V conversion IR9331 Horizontal amplitude control chopper Horizontal drive Horizontal output Power unit To be added for MM Model change For MM RGB RF VIDEO L R D L Signal switching AN5862K Resonance capacitor switching L R V C D TA8801 OSD R G B R G B ...

Страница 9: ...dicators P 10 Local Keys 8key 11 Front Surround 12 Sub Bass System 13 Audio Output 5W x 2 14 Speaker Size Nbr 80 x 120 x 2 15 Comb Filter GLS 16 Black Level Expand 17 Horizontal Resolution 500 18 Parental Ch Lock 19 Channel Caption 20 Off Timer 180min 21 Channel Search 22 S Video In Term 1 23 Audio Video In Term 1 24 Variable Audio Out RCA Jack 25 RGB Audio L R 26 Mini D Sub 15pin 27 Rod Ant Adapt...

Страница 10: ...110 0 x 330 0 Video CRT D PB5228 2 119 0 x 210 0 D Sub PB5228 3 28 5 x 41 5 Printed wiring board part code P P M P 23534680B Printed wiring board part code P P M P 23534679B Printed wiring board part code P P 23534681B M P 23534681C 249 x 330 drop Hole draw ing New Hole drawing New 249 x 330 Hole drawing New 249 x 330 Hole drawing New SIGNAL VIDEO V CUT LINE drop D SUB Hole draw ing New POWER V CU...

Страница 11: ...ceivers TMP87CM34N 42pins built inCCD developedbyToshiba is employed With this microcomputer each IC and circuit shown below are controlled 2 1 1 Non volatile Memory IC ICA02 NEC µPD672CX 1 Memorizes data for video and audio signal adjustment values soundvolume wooferadjustmentvalue external input status etc 2 Memorizesadjustmentdataforwhitebalance RGBcut off GB drive sub brightness sub color sub ...

Страница 12: ...IT PICTURE CONTROL AUDIO CONTROL TUNER IF DAC1 DAC2 5 6 7 STB CLK DATA 9 AFT 37 38 SCL SDA Y B G R 25 24 23 22 MEMORY µPD6272CX QA02 DPG MTS H PULSE V PULSE 6 13 MHz TRF1147T 8MHz CLOCK TCR1056 26 27 28 29 31 32 33 34 42 21 HD VD OSC1 OSC0 X1 X0 RST HOLD VDD VSS RESET CIRCUIT 5V GND 35 36 RMT SYNC 1 RELAY 15 MODE 13 14 KEY A KEY B 10 EXIT A QA01 TMP87CM34N 3101 ...

Страница 13: ... input 0 5V 16 17 Y IN 18 B IN 19 G IN 20 R IN 21 VSS GND 22 R 23 G 24 B 25 Y 26 HD H sync pulse input 27 VD V sync pulse input 28 OSC1 29 OSC0 30 TEST For microcomputer shipping test Fixed low level 31 X IN 32 X OUT 33 RESET Negative logic 34 STOP Negative logic 35 RMT Remote controller signal det Negative logic 36 SYNC Sync pulse signal input 37 SCL I2 C BUS CLOCK 38 SDA I2 C BUS DATA 39 TC1 GND...

Страница 14: ...SHARP SHARPNESS O 0 5V 14 BRT BRIGHTNESS O 0 5V 15 CONT CONTRAST O 0 5V 16 VCC POWER SUPPLY 2 DAC QX001 Terminal No Terminal name Function I O Logic 1 VDD INTERFACE POWER SUPPLY 2 DAT T BUS DATA INPUT TERMINAL I 3 CLK T BUS CLOCK INPUT TERMINAL I 4 PRD T BUS PERIOD INPUT TERMINAL I 5 RESET 6 SUB ADDRESS CHANGEOVER TERMINAL O 7 TV RGB TV RGB SWITCH TERMINAL O TV L RGB H L at RGB NO SIG 8 9 MUTE VID...

Страница 15: ...OPTION K22 15H TIMER K23 16H SET UP K24 17H CH RTN K25 18H K26 19H CONTROL UP K27 1AH VOL UP K28 1BH CH UP K29 1CH RECALL K30 1DH CONTROL DN K31 1EH VOL DN K32 1FH CH DN K33 40H K34 41H K35 42H K36 43H K37 44H K38 45H K39 46H K40 47H K41 48H K42 49H K43 4AH K44 4BH K45 4CH K46 4DH K47 4EH K48 4FH Key No Data code Function Conti nuity K49 50H K50 51H K51 52H K52 53H K53 54H K54 55H K55 56H K56 57H ...

Страница 16: ...ey circuit below when one of key among S13 1 to S13 7 is pressed the VIN which corresponds to the switch is applied to input terminal pin 13 Judgement of key input is done by measuring what voltage VIN is at the pin Voltage measuring and key judgement are performed by A D converter in Micom and by the software KEY No Function S13 1 POWER S13 2 CH UP S13 3 CH DN S13 4 VOL UP S13 5 VOL DN S13 6 ADV ...

Страница 17: ... WA 4 WA 3 WA 2 WA 1 WA 0 7 8 9 ACK OUT D 7 D 6 D 5 D 4 D 3 D 2 D 1 D 0 ACK OUT IN IN IN Slave address R W command input 1 0 0 ACK signal output ACK signal output Write data input Fig 2 1 4 2 Read Mode SDA SCL Start bit issue ACK signal output Word address input R W ACK OUT 0 A2 1 A1 0 1 1 5 2 4 3 6 7 8 9 IN IN WA 7 WA 6 WA 5 WA 4 WA 3 WA 2 WA 1 WA 0 0 A2 1 A1 1 0 0 R W ACK OUT D 7 D 6 D 5 D 4 D 3...

Страница 18: ...ST AC Read mode S Slave address 8 bits RW AC Word address 8 bits Data 8 bits AC ST AC Slave address 8 bits AC 2 DPC IC S Slave address 8 bits RW AC Data 8 bits AC ST AC Sub address 8 bits A0H WRITE 8CH SCL terminal SDA termianl Start condition Data transmission Acknowledge signal Stop condition SCL terminal SDA termianl 1 5 2 6 3 7 4 8 9 D7 D6 D5 D4 D3 D2 D1 D0 ...

Страница 19: ...C Slave address 8 bits FM 8 bits FL 8 bits CO 8 bits AC AC BA 8 bits Main screen tuner COH FM Variable divider control byte FL Variable divider control byte CO Charge pump sensitivity switching bit and test mode bit BA Band switching bit ...

Страница 20: ...e The operation of key that accompanies display of other than from 1 to 4 makes the mode cancel During servicing in RGB mode changing of the mode of RGB causes cancellation 6 Other service function MUTE key Shipping out preset RECALL key Initializing of memory Address Adjustment contents 161H Video section sub adjustment 1E2H OSD horizontal starting position 120H Deflection section sub adjustment ...

Страница 21: ...TER 118H SPECTRAL 119H WIDEBAND Address Adjustment contents 161H SUB BRIGHT 107H SUB COLOR 163H SUB TINT 108H SUB CONTRAST Address Adjustment contents 1E2H OSD H POSI Address Adjustment contents 120H PICTURE HEIGHT 121H V LINEARITY 122H V S CORRECTION 123H V SHIFT 125H PICTURE WIDTH 126H E W PARABOLA 127H E W CORNER 128H KEYSTONE 12AH V CORRECTION 111H HORIZ POSITION 112H VERT POSITION a Video sec...

Страница 22: ...C501 TA8801ANareselectedbyIC216AN5862KandICR03 AN5862K and are output at pins 5 6 8 of ICR03 AN5862K 4 TV RGB switching pulse output from ICX001 TB1203AP OSD switching pulse output from microcomputer and blanking pulse are input to OR gate circuit And output from OR gate is input to pin 4 of ICR03 AN5862K These operations function as following 3 items In TV mode output from ICR03 AN5862K is turned...

Страница 23: ...splayed on screen 4 Cut off and Drive controls can be adjusted with R952 and R954 1 OUTLINE CRTDrivecircuit isdesigned withitsoutputloadresistance decreased to obtain wide frequency band and heat sink of output transistor is enlarged in size Cut off control and DrivecontrolofTVsignalareadjustedwithvariableresistors on CRT drive circuit otherwise RGB signals are adjusted by biascontrolandgaincontro...

Страница 24: ...tify VGA signal or not horizontal scanning frequency is higher or lower than 28kHz the signal is input or not NO SIGNAL DISCRIMINATION ICH01 QH06 POLARITY DISCRIMINATION ICH01 FREQUENCY DISCRIMINATION ICH04 ICH05 DECODER ICH02 No signal VGA480 VGA400 VGA350 Hor sync Vert sync Low frequency Fig 1 VGA has three modes by number of vertical line These are made to be able identify by polarity of horizo...

Страница 25: ...e Macintosh 13Ó 640 x 480 35 0kHz 67Hz Sync on Green or Composite Sync VESA VGA 640 x 480 37 9kHz 72Hz Negative Negative Table 2 Roughly classified they are of two shapes one is like Macintosh SYNC ON GREEN which is imposed on video signal and the other is the output in TTL level separated from video signal The TTL level method is classified to Composite Sync which combines horizontal and vertical...

Страница 26: ... of sync signal and the logic output is shown in Table 3 ICH02 is Decoder IC TC4028BP and the truth table is shown in Table 4 Input at pin 6 H COMP Input at pin 8 V Output pin 1 2 18 19 H COMP POS H COMP POS H COMP POS NON V POS V NEG H H H L H H L L L L L H H COMP NEG H COMP NEG H COMP NEG NON V POS V NEG H H H L H H H H H L L H NON NON NON NON V POS V NEG L L L L H H L L L L L H Table 3 Logic ou...

Страница 27: ...T1200 8 7 6 5 ICH04 IR9331 F V CONVERTER 1 2 3 4 14 13 12 11 10 9 8 DH04 RH22 560KG RK58 33KG DK17 RH23 1 8KG RK59 12KG RH20 1 4W 47KF RH21 1 4W11KF ICH05 TA75902P or LM2902N 1 2 3 4 5 6 7 F V RH75 8 2K CK17 M680 1SS176 or 1SS133 1SS176 or 1SS133 CH15 16V47 RH11 15K RH10 18K QH03 2SC752Y RH64 33K QK11 2SC1815Y or 2SC17405 Q or 2SC1685Q CK24 M0 015 CH14 M2 2 RH18 1 4W 82KF RH16 1 4W4 7KF RH17 2KB F...

Страница 28: ...l is input to pin 6 of IC through QH03 this performs as a trigger charge of capacitor CH13 which is connected to pin 5 begins Voltage at pin 5 is comparedwithreferencevoltage Vccx2 3 bythecomparater inside IC and the voltage finally reaches the reference voltage to reverse the comparater This reverse operation discharges the capacitor rapidly Next when hor sync signal comes this operation is again...

Страница 29: ...es it is used to switching of circuit operation at some points in the hor deflection circuit As understanding from the above formula at pin 1 the voltage which is proportional to frequency of hor sync signal is obtained QK11 performs the function to prevent picture bending on screen by the increase of F V convert voltage because the period of equalized pulse is seemed as twice of frequency when co...

Страница 30: ...ogic Green Sep Filter Green IN Green GND Comp H Comp H Det H Det Vert Comp H IN Vert IN Vert Det Vert S S Adj Table 6 Priority order of output Sync signals are input as follows TTL level hor sync or compositesynctopin6 TTLlevelversynctopin8 andSync On Green sync to pin 4 Output signals are as follows Positive ver sync at pin 13 Positive hor sync at pin 14 and Negative hor sync at pin 15 When plura...

Страница 31: ...m to circuits Thememoriescontrollingthisdeflectioncircuitareequipped by 1 set for TV mode and by 4 sets for RGB mode In RGB mode 3 sets are used for VGA and reminder 1 set is used for Macintosh and other signal than VGA And when signal is not input in RGB mode micom supplies switching signal so that deflection circuit only operates in TV mode When frequency of input signal is lower than 28kHz mico...

Страница 32: ...from a video signal and feeds it to an H and V deflection circuits Theseparationcircuitconsistsofanamplitudeseparation H and V sync separation circuit and a frequency separation circuit V sync separation circuit which performs the separationbyusingafrequencydifferencebetweenHandV In the N4ES chassis all these sync separation circuits are contained in a V C D IC TA8801AN Fig 1 shows a block diagram...

Страница 33: ...scanning time base of the transistor is set to a negative potential for a long period Thatis thesyncseparationtransistorisreverse biased and becomes non conductive status for the video signal period thus only the sync signal is extracted The sync signal obtained in this stage is fed to the H AFC circuit and V integration circuit 2 2 V Sync Separation Circuit To separate a V sync signal from the co...

Страница 34: ... 0 1µ 330k 0 015µ V SYNC 1µ 12V 18k Vvs 5k VRS V BLK V D 0 01µ 3300p 100µ 0 01µ 160p 22k 30k H LOCK FBP H D 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 V Ref V OSC RAMP G V OUT H LOCK SAW M M H OUT COMP H OSC AFC V I 2nd delay 1st delay 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 To 14pin To 14pin To 14pin To 14pin To 14pin EN 0 01µ H SYNC 22k 0 01µ 0 01µ 0 01µ 4 7µ 1200p 12k VR2 5k VR3 5k 560p VR1 5k 12...

Страница 35: ...age is 2 5V phase of FBP become most delayed condition to hor sync signal The hor phase shift controlled by this terminal is decided by time constant connected to pin 4 and is independent of hor osc frequency of pin 11 80K 180 C1 H SYNC 0 01 1 Fig 2 2 Pin 2 is ENABLE terminal of hor sync signal When this terminal is open voltage of this terminal turns LOW condition by inside bias of IC Atthetime h...

Страница 36: ...to pin 18 always constant when voltage of this terminal is turned to 0V phase difference does not change with the change of hor osc frequency And when the voltage of this terminal is turned to 2 5V phaseofFBPiscontrolledtothedelayedtendencycomparing to hor osc frequency input at pin 1 Longer the period of hor osc frequency is more delayed the tendency is 6 Timeconstantofpin6decidesthephaseshiftcon...

Страница 37: ...o be coincide together by the AFC circuit Thecontrolvoltageofpin8andthehorfree runningfrequency fH are represented by the following expression Fh 2 3 1 11 5CR V8 1 Here V8 Control voltage of pin 8 C External capacitor of pin 11 R External resistor of pin 9 7 Pin 7 is connected with capacitor which smooths AFC comparing waveform Infigure Vsigisthesamesignalasthecomparingwaveform made at pin 22 8 Pi...

Страница 38: ... 13 Pin 13 is a low pass filter giving band limit to hor osc circuit 1 5K 13 1000pF Fig 14 14 Pin 14 is Vcc terminal of horizontal block Since pin 14 has approx 9V regulator inside IC current of approx 60 mA is applied at this pin 15 1 5K Fig 15 16 Pin 16 is hor output terminal The output voltage is approx 5V when the terminal is set in high impedance And output current becomes approx 2mA when the...

Страница 39: ...nt of this pin 920U MAX 22 100 30 5K 3300pF Fig 20 23 Pin 23 is GND terminal of Ver block 24 Pin 24 is ver output terminal The output voltage is approx 5V when the terminal is set in high impedance And output current becomes approx 2mA when the terminal is connected to ground through 100 ohm Internal transistor can accept current of approx 10mA HIGH period of output is 300 µs and it is independent...

Страница 40: ...endedvalueis0 015µF andifthisvalueofcapacitor is increased respective absolute or maximum values of Tvshift Tvd pin 24 output and Tvd vblk pin 25 output can be enlarged keeping the conditions below 2K 0 5V 100 68K 25 Fig 22 26 Pin 26 is V SHIFT terminal The control voltage range is 0 to 2 5V When this terminal voltage is 0V ver output of pin 24 rises at the same time as ver sync signal By controll...

Страница 41: ...e acceptable and the sync is triggered at front edge of sync signal 100 28 330K Fig 26 29 Pin 29 is a terminal to connect ver osc capacitor Using recommended 0 1µF 10 allows ver sync signal ranging from approx 50Hz to 160Hz to be pulled in with no adjustment To shift the pull in range upper or lower the valueofthiscapacitorisselectedtosuitablevalue Supposing this capacitor is increased the pull in...

Страница 42: ...uit which is consisted of QK13 CK25 and RK50 operates to eliminate sync pulse only for period of ver sync so that in RGB mode top edge of picture does not show AFC bending affected by ver sync when composite sync is input ThesyncsignalsappliedtoOSC IC ICH08arebothpositive Hor sync pulse is supplied to F V convert circuit as well ICH01 M52346SP 14 13 6 8 Vert Hor RGB input Hor sync Vert sync TV mod...

Страница 43: ...ntthoughQH17 SeeFig 29 When the mode is selected with remote unit or key of TV set channel selecting IC sends data which makes voltage at pin13 of DAC ICX001 5V or 0V using T Bus line This voltageatpin13ofDACissuppliedtobaseofQH17through buffer amp QX02 This voltage becomes 5V in RGB mode and 0V in TV mode Fig 30 2 3 Hor Phase Shift Circuit The circuit can adjust hor picture position by utilizing ...

Страница 44: ... 001 RH34 1 4W1KF RH80 18K RH81 39K CH37 50V 10µ CH36 16V 330µ RH79 1 5K RH36 1 4W 750F NTSC fH ADJ RH35 5008 QH15 RN1203 2 1 3 QK13 2SC1815Y or 2SC1740S Q VFV RH82 2R47 RGB fH ADJ 1 2 3 V BLK CH17 50V 1µ ICH08 LA7860 H V OSC VHP 0 5V AFC Fig 32 2 4 Other Circumference Circuit QH15 changes the duty ratio of hor output pulse that is hor drive pulse of ICH08 so that the base current of hor output tr...

Страница 45: ...circuit and pump up circuit circuits are included in IC301 TA8427K ICH08 LA7860 SYNC CIRCUIT V TRIGGER IC302 TA8859AP SAM TOOTH WAVE GAIN CIRCUIT AMP LOGIC CIRCUIT IC301 TA8427K PUMP UP CIRCUIT OUTPUT Microcomputer CENTERING CIRCUIT DEFLECTION YOKE Fig 1 Block diagram of V deflection circuit 1 1 Theory of Operation The purpose of the V output circuit is to provide a sawtooth wave signal with good ...

Страница 46: ...ariations of input pulse width The pulse generation circuit also works to fix the V ramp voltage at a reference voltage when the trigger pulse enters so it can prevent the sawtooth wave start voltage from variations by horizontal component thus improving interlacing characteristics WAVEFORM SHAPE TRIGGER DET PULSE GAIN V LAMP AGC R329 C321 C322 C323 12V DC 0V 14 15 16 Fig 4 C332 12V R329 15 14 13 ...

Страница 47: ...rrent to flow into the deflection yoke R305 C306 DY Q4 These operations are shown in Fig 5 Fig 5 V output circuit InFig 6 a thepowerVccisexpressedasafixedlevel and the positive and negative current flowing into the deflection yoke is a current d current b c in Fig 6 and the emitter voltage of Q3 and Q4 is expressed as e Q3 collector loss i1 x Vce1 and the value is equal to multiplication of Fig 6 ...

Страница 48: ...8 Since pin 7 of a transistor switch inside IC301 is connected to the ground for the scanning period the powersupply pin3 oftheoutputstageshowsavoltage of VCC VF and C308 is charged up to a voltage of VCC VF VR for this period Last half of flyback period Current flows into L462 D1 C308 D308 VCC 27V GND R305 C306 L462 in this order and the voltage across these is VP VCC VF VCC VF VR VF about 58V is...

Страница 49: ...so that user can adjust picture to desired position on screen in spite of various signals which exist as input signals in RGB mode Fig 9 SupplyingcurrenttoQ309fromdeflectionyokeL462causes picture position to move up in reverse supplying current to L462fromQ308causespositiontomovedown Thiscontrol can be done by remote control unit or key on TV set Micom IC sends data to DAC IC ICX001 via T Bus line...

Страница 50: ...y TV The circuit description is as follows 1 DEFLECTION CIRCUIT 1 1 Outline Fig 1 is block diagram Fig 1 TH02 is a transformer corresponding to FBT of ordinary TV set and from which AFC pulse and BLK pulse are taken out Thepowersourceproducedfrompins4to6ofthetransformer let the hor centering circuit which moves raster left and right operate In ordinary TV size and side pincushion distortion are ad...

Страница 51: ...rns off collector current reduces to zero and the deflection current stops to increase 3 t2 t3 Thedrivevoltageturnsoffatt2 butthedeflectioncurrentcan not reduce to zero immediately bacause of inherent nature of the coil and continues to flow gradually decreasing by charging the resonant capacitor C0 At the same time the capacitor voltage or the collector voltage is gradually increases andreachesma...

Страница 52: ...flection scanning a current flowing through the damper diode scans the left halfof the screen the current developed by the horizontal output transistor scans the right half of the screen and for the flybackperiod boththedamperdiodeandtheoutputtransistor are cut off and the oscillation current of the circuit is used Using the oscillation current improves efficiency of the circuit That is about a ha...

Страница 53: ...lowly at the circumference area as shown in Fig 4 In the horizontal output circuit shown in Fig 5 capacitor Cs connectedinserieswiththedeflectioncoilLHistoblockDC current By properly selecting the value of Cs and by generating a parabolic voltage developed by integrating the deflectioncoildcurrentacrosstheScapacitor andbyvarying the deflection yoke voltage with the voltage the scanning speed is de...

Страница 54: ...cturesatleftandrightsidesofthescreen left side expanded right side compressed WhenahorizontallinearitycoilLI withacurrentcharacteristic as shown in figure is used left side picture will be compressed and right side picture will be expanded because the inductance is high at the left side on the screen and low at the right side The left right asymmetrical correction is carried out in this way and pi...

Страница 55: ...fhoroutputtransistor varies with the resonant frequency of retracing period And thisfrequencydependsontheinductanceofdeflectionyoke the primary inductance of transformer TH02 corresponding to FBT and the resonant capacitor The value of this flyback pulse is in proportion to voltage of power source and is in reverse proportion to scanning frequency Sincethismodelismulti scanning itchangespowervolta...

Страница 56: ...shown by solid line in Fig 8 to flow via primary winding of TH02 and moves raster right In reverse rotatingtheslidertopin1ofRK17allowsthecurrent as dotted line to flow and moves raster left This shifting value varies with frequency of input signal This is the reason why output voltage of chopper regulator varies with frequency of input signal and voltages obtained across CH61 and across CH62 chang...

Страница 57: ...and effective Fig 9 The chopper regulator can be controlled to obtain the best quality of picture That is as shown in Fig 10 size is enlarged by increasing d c voltage and correction of pincushion distortion is enhanced by increasing parabola element which is added modulation with ver sync like dotted line in Fig 10 0 Fig 10 Output voltage of regulator D S G RK06 DK04 CK10 DK03 CK11 RK81 TK01 1 3 ...

Страница 58: ... ratio of Ton and Toff output can be stabilized The current iL in the time when FET is on is AndjustbeforeTrisoff maximumvalueiL2ofiLbecomes After FET turns off the current flowing to flywheel diode is expressed as below As output current Io is equal to average of iL Ton 5 2L 2 Io iL1 iL1 iL2 When Io becomes small iL1 becomes small To control circuit stably current iL of choke coil is required to ...

Страница 59: ...ged in CK11 Inperiodthatthesecondarypulseisnegative throughDK01 CK11 is rapidly charged to the peak value of pulse by supplying current as solid line in Fig 9 In the next when positive pulse comes pulse generated across the secondary of transformer and voltage stored in CK11 Fig 12 d d are superimposed andareaddedtogateofFET Bythisway the gate voltage does not depend on duty ratio and becomes cons...

Страница 60: ...cuit employs timer IC ICK01 TA7555P CHOPPER REGULATOR ICK01 TA7555P 7 6 5 2 3 QK05 QK14 QK07 16 ICH08 LA7860 T BUS ICX00 DAC ICA01 MICOM 11 ICK09 IC302 TA8859AP RH35 NTSC fH ADJ ICH04 IR9331 ICH13 ICH05 ICK02 5 6 7 5 6 7 ICK09 Correction voltage of pincushion distortion F V conversion voltage RK73 1 15 2 13 12 14 4 10 9 8 Adjusting voltage of H SIZE I C BUS 2 ICK02 3 2 1 RK07 RK23 RK08 RK09 QH26 T...

Страница 61: ...ntentionally the regulation is not so effectivelyperformedastoeliminatevoltagerippleperfectly Iftheperfectregulationisdone powerconsumptionsupplied to FBT increases so much when white peak current flows and big burden is applied to chopper regulator in control operation For designing of compact circuit the distortion is corrected with less extent of regulation and picture quality is kept QK10 is a...

Страница 62: ...ut stage of chopper turns on in period that this pulse is HIGH Therefore to raise output voltage of chopper it is necessary that the period of high level of pulse at pin 3 is made wide And it will be understood that this is accomplished by increasing control voltage at pin 5 Since pulse at pin 3 is always fallen down to LOW level at front edge of reset pulse of pin 4 it is surely kept in LOW level...

Страница 63: ...ng over as explained in the section HOR OSC CIRCUIT isdoneatfrequencyofarround28kHz andQH15 is used for the element Not only duty ratio is switched over but also amount of current is changed This is caused by that the base current gradually decreases from the initial value in therateofslopewhichisdecided byinductanceofsecondary winding of drive trans Since period of flowing current is long when fr...

Страница 64: ...he explanation is omitted here Error amp consists of pins 1 to 3 of ope amp IC407 Pins 5 to7arethebufferamptodetecthighvoltagefromFBT High voltage can be adjusted by rotating variable resistor R451 C406 is used to adjust amount of ripple element of high voltage to detect Fig 19 CHOPPER REGULATOR FOR HV CONTROL QH24 180V 5 ICH20 TA7555P Deflection Circuit Video Out X Ray Port 1 X Ray Port 2 70 140V...

Страница 65: ...se peak value of flyback pulse Therefore the circuit is designed so that the reference voltage of error amp is for a moment reduced just before the relay opens and high voltage is kept down Focus pack of FBT unlike in TV produces focus voltage Fv and screen voltage Fs by dividing high voltage Accordingly in this model high voltage does not remain for a long time after power switch is turned off 20...

Страница 66: ...hes This phenomenon tends to happen because d c elementbecomeslargebydecreasingofpowervoltageunder lower frequency and results in short period of damper Therefore it is necessary that in high voltage side period of base current flowing is made long Damper period TD becomeslong becaused c elementexistslittleinDeflection side Because drive pulse is commonly used in High voltage side and in Deflectio...

Страница 67: ...n due to damage of associated parts etc or hazard such as excessive heat etc may occur This model has a protection circuit whitch cuts off the relay under abnormal conditions by detecting a current of the 180V line Fig 1 shows the overcurrent protection circuit If a load of the 180V line is short circuited and the current increases excessively a voltage drop will occur across R876 When base emitte...

Страница 68: ...reases With the ED increased and emitter voltage of Q471 which is divided by R463 R465 exceeds D472 zener voltage 6 2V Q471 VBE 0 7V Q471 turns on and a base current flows into Q472 Then Q472 turns on and a gate voltage is applied to a thyrister D862 The thyrister D862 turns on and drops base voltage of Q863 which is driving a relay to zero so the relay iscutoff SincethethylisterD862isconnectedtot...

Страница 69: ...e turn on to let operation of hor deflection circuit stop Turning on of QH45 make short to ground the trigger pulse which is supplied from QK14 to chopper regulators of deflection circuit and high voltage circuit and for the reason the both circuits stop operation to prevent X ray radiation Once this circuit operates the situation is held until power switch is turned off Fig 3 5 6 4 D471 R469 D474...

Страница 70: ... no problem in hor sync signal but Vp which is used as ver sync signal has problem cause by the fact that hor osc circuit inside V C D IC is not in synchronization If Vp is used in ver sync signal as it is screen picture trembles up and down This is the failure cause by variation of the timing that Vp pulse appears For the countermeasure switching over circuit in Fig 1 is employed Fig 1 IC501 TA88...

Страница 71: ...cuit But since the timing is later than the ver sync signal taken from integral of SYNC OUT pulse influence of Vp pulse does not appear and the said failure of trembling does not happen When ver sync signal is lost from SYNC OUT pulse due to radio wave interference like ghost the way to choose is to rely on Vp pulse Since operation frequency of ver deflection circuit variesconsiderablybythenoiseof...

Страница 72: ... not happen In this way complex switching circuit is added to manage V C D IC for TV well IC501 TA8801AN H Osc H Out AFC H sync signal Mono Multi ICH08 LA7860 H Drive Deflection Out H Osc H Out AFC False sync signal a IC501 TA8801AN H Osc H Out AFC H sync signal Mono Multi ICH08 LA7860 H Drive Deflection Out H Osc H Out AFC False sync signal b Mono Multi Fig 3 Loop of AFC circuit ...

Страница 73: ...ctionsdoesnotbecomeasillustrated correct by cutting magnet Z2007A PC23102959 by 15mm SECTION XII PICTURE TUBE 25 1mm Purity magnet DY CPT Fig 12 1 VIN 5 START O V P T S D REGULATOR LATCH TON OSC R2 TOFF R1 TR1 C1 R3 C2 7 SS 6 AMP C3 3 4 GND Ios O C P R4 DRIVE 1 2 D S Fig 12 2 20V FS D T Items Model MM20E45 CPT type name A51JRU76X QI PC 2312610 DY type name TDY 8211A PC 23231117 CPM type name MGA 1...

Страница 74: ...ts and partial resonant operation FILTER CIRCUIT AC Fuse STANDBY POWER SUPPLY DEGAUSSER RELAY 3 TERMINAL REG WITH RESET RECTIFIER CIRCUIT MAIN SWITCHING POWER SUPPLY Microcomputer system Chopper regulator 3 TERMINAL REGU V901 CRT HEATER 182V line 30V line 20V line QH24 following to T461 FBT IC301 T401 TH03 V OUT IC601 AUDIO OUT IC501 ICR02 ICR03 12V 12V 9V 5V ICV01 H001 etc H001 TUNER IF etc ICH08...

Страница 75: ...ig 12 3 Block diagram of STR M6511 Terminal No Symbol Name Function 1 D Drain terminal MOS FET drain 2 S Source terminal MOS FET source 3 GND GND terminal GND 4 IOS Overcurrent terminal Overcurrent detection signal input 5 VIN Power supply terminal Control circuit power supply input 6 Amp Feedback terminal Voltage regulator control signal input 7 SS Soft start terminal Soft start voltage output Ta...

Страница 76: ... smoothed with DQ05 and CQ15 Thus obtained voltage is fed to the VIN terminal pin 5 Since the voltage does not reach the specified voltage level afteroperationofthecontrolcircuit theVIN terminalvoltage beginstodrop Butastheoperationstopvoltageissettoalow voltage of 10V TYP the subwinding voltage reaches the setting value before the VIN terminal voltage reaches the settingvalue thus thecontrolcircu...

Страница 77: ...C2 drops with a slope determined by multiplication of C2 and R3 When the voltage across C2 drops to about 3V the oscillator outputisinvertedagainandtheMOSFETisturnedon Atthe same time C2 is rapidly charged up to about 5V again Operations described in the previous page are repeatedly conducted and the on off operations of the MOS FET is also repeated In this way C3 is charged with a voltage shown i...

Страница 78: ...is also turned on Forthisperiod aresonanceoccurswithatransformerLP and CQ09 2p LC and CQ12 controls delay time of the on time for the transistor thereby setting a parameter for the bottom point of the resonant voltage and reducing on loss considerably in addition to reduction of switching noises Fig 13 10 DQ03 works as a clamp diode to suppress a negative charge voltage of the integration circuit ...

Страница 79: ...inal voltage drops In this way when the latch circuit is operating the VIN terminal voltage increases and decreases between 10V TYP and 16V TYP thereby preventing the VIN terminal voltage from excessive increase or protecting QQ01 Fig 13 16 shows VIN terminal waveforms when the latch circuit is working Releasing of the latch circuit is conducted by lowering the VIN terminal voltage to a value less...

Страница 80: ...a 182V error amplifier by adding a 20V zener diode DQ13 and 22V DQ14 A voltage detected by QQ08 is converted into a DC voltage and applied to pin 6 of QQ01 throughaphotocouplerQQ03tovarytheoscillatorfrequency and on time thereby stabilizing the secondary side rectified output voltage 3 2 Rectification Circuit The 182V line voltage is rectified and smoothed by DQ08 and CQ20 CQ16 RQ15 CQ17 LQ06 CQ18...

Страница 81: ...urned on Then the relay on offtransistorturnsoffandopenstheACrelay thusthepower supply circuit stops the oscillation 3 4 Overcurrent Protection Circuit The overcurrent protection circuit is also provided to open the AC relay SR81 and to stop oscillation of the power The 182V line load is always monitored with R876 When the voltage of R876 exceeds the bias of Q870 VBE about 1 0V Q870 and D870 turn ...

Страница 82: ...S 1 No On screen Display RGB Mode No on screen display Check waveforms at pins 20 24 28 of ICR02 Check voltage at pin 4 of ICR03 0V Check waveforms at pins 5 6 8 of ICR03 Check CRT drive circuit Replace ICR02 Replace ICX001 Replace ICR03 NG NG NG ...

Страница 83: ...rcuit NG NG OK 1 9V Check pin 3 of IC302 is 12V Replace IC302 NG Check pin 62 output of Q501 with synchronous scope 5V OK NG NG Check voltage of pin 21 ICH08 CH18 and RH99 Replace Q501 Check repair and replace FQ03 DQ10 CQ27 CQ37 LQ15 and TQ01 Check and repair L462 R303 R304 R305 R306 in vertical output circuit Check and repair QH42 D307 IC302 RH61 and R320 Check and repair CH18 or RH99 Check and ...

Страница 84: ...d at pin 16 of ICH08 Is drive pulse generated at pin 3 of ICH20 Is voltage at pin 7 of IC407 higher than 5V Check and repair FQ01 DQ08 CQ21 TQ01 Q404 QH24 QH30 and QH25 Check and repair ICH08 and 12V power supply Check and repair QH24 Check and repair IC407 ICH20 and associated circuit Check and repair FBT L401 and pattern from QH24 Check and repair Q401 T401 and associated circuit Check and repai...

Страница 85: ...or of QH30 higher than 30V Is voltage at both ends of CH55 higher than 30V Check and repair chopper regulator ICK01 ICK02 TK01 QH25 and associated circuit Check and repair DY LH04 CH65 P401 and pattern Check and repair drive circuit QH33 TH03 QH30 and associated circuits Check and repair TH02 and pattern NG NG NG ...

Страница 86: ...turned on check 180V line voltage with oscilloscope Less than 205V With SW turned on check 20V line voltage with oscilloscope Less than 35V With SW turned on check voltage across C471 with oscilloscope Less than 42V Check C867 D862 D878 Q863 R875 R877 and repair Higher than 205V Higher than 42V Higher than 35V Check over current protection circuit H deflection circuit and D870 Q870 R870 R873 R876 ...

Страница 87: ...ircuit Check and repair D862 Check and repair D471 R472 Check and repair around pin 5 of FBT OK OK NG X RAY Protection Circuit 2 Failure Diagnosis Procedures X ray protection circuit does not work when X 2 and R 2 terminals are connected Check voltage at D474 cathode 37 39V Check and repair DH15 QH45 R473 R474 and associated circuit Check and repair DH14 Check and repair D474 R469 Check and repair...

Страница 88: ... Check F801 Check standby power supply across C840 Check micro computer power supply Q840 output and reset voltage Check voltage at pin 33 of QA01 Check voltage at pin 33 with Q862B Q863C opened Check Q862 Q863 and repair Proceed to PROTECTION CIRCUIT DIAGNOSIS PROCEDURES Replace F801 Check C840 D840 D843 T840 and repair Check Q840 and 5V load reset circuit and repair Check Q862 SR81 and repair Ch...

Страница 89: ...k voltage across CQ41 with 7V load opened Check CRT heater and repair Check voltage across CQ27 with 30V load opened Check IC301 and repair Check voltage across CQ24 with 20V load opened Check IC601 and repair Check CQ29 FQ04 DQ11 TQ01 and repair Check CQ41 CQ42 FQ05 DQ15 TQ01 and repair Check CQ27 CQ37 FQ03 DQ10 TQ01 and repair Check CQ24 FQ02 DQ09 TQ01 and repair 0V 15V 15V 0V 7V 0V 0V 7V 30V 0V...

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