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Training Manual

Circuit Description and Troubleshooting

Course: CTV-25

Color
Television

BA-4 Chassis

Содержание CTV-25R1

Страница 1: ...S Training Manual Circuit Description and Troubleshooting Course CTV 25R1 Color Television BA 4 Chassis ...

Страница 2: ...ut Stage 17 The Power Output Control 17 Converter 19 The Rectifier 19 The Oscillator 19 Converter Voltage Outputs 29 B Regulation 13 20 TV 33 Regulation 33 Additional Circuits 33 Power Supply Block 27 Models 37 Standby Power Supply 39 Basic Oscillator 39 Additional Components 41 B Regulation 27 TV 45 Regulation 45 Soft Start Circuit 45 Power On Communications Block 47 Degaussing Circuitry 49 Conce...

Страница 3: ...ion Circuit 75 Troubleshootintg 77 Video Block 27 With PIP 79 Picture in Picture PIP Board Signal Flow 79 Picture in Picture Processing 81 Deflection Block 83 Vertical Deflection 85 Horizontal Deflection 89 Protection 93 Troubleshooting 95 Self Diagnostic 99 Timer Standby Light 99 Self Diagnostic On Screen Display 99 Self Diagnostic Circuit 101 ...

Страница 4: ...and provide tips for troubleshooting where needed Some parts of the circuit are used only under certain conditions of operation It is important to know when these additional parts affect the main circuit during operation and how they affect the main circuits if they are defective Provide some voltages from a working production run set that are not supplied in the service manual These can be compar...

Страница 5: ...strial magnetism Prevents adjacent and stray electrons from striking the wrong phos phor Allows more electrons to pass increasing brightness without short ening life Results in a flat screen This reduces annoying room light reflections glare The remainder of this document is divided into four sections explaining the construction of Trinitron tube as an aid to the service technician The Trinitron E...

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Страница 7: ...re tube is said to be in cutoff On the other hand placing the cathode at the same potential as grid one 0Vdc is the same as if grid one were invisible The maximum amount of electrons is attracted toward the positive grid two structure resulting in maximum screen brightness By varying the voltage at the cathode from 0 Vdc to 200Vdc cutoff the amount of electrons available to the gun structure to pr...

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Страница 9: ...es one gun which three electron beams pass through These three beams diverge as they pass out of the gun Electrostatic convergence plates bend the outer electron beams back so they land adjacent to the center electron beam on the corresponding red and blue phosphors Four convergence plates are used to bend the outer electron beams The two center plates are connected to the flyback generated high v...

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Страница 11: ... produces a dark area at the left and right sides of the picture tube Increasing the current through the horizontal windings of the yoke com pensates for this hourglass picture The yoke current is then gradually increased line by line until the middle of the picture for maximum width the curve is reduced as the beam continues to scan downward The result is a straight picture This type of yoke dist...

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Страница 13: ...ents in the picture The resultant compounds that are cre ated coat the inside walls of the picture tube without consequence The Picture Tube Defect Symptoms Several problems can occur in new picture tubes The bench technician can solve some problems and avoid a picture tube replacement result is a longer tube life because of the cleaner environment Defective Picture T ube S ym ptom s Sym ptom Susp...

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Страница 15: ... is d a n g e r o u s a n d m a y c a u s e tu b e im p lo s io n U s e a ll s a fe ty p re c a u t i o n s D o n o t ja r s e t T ra n s p o rt fa c e d o w n P u rity B e a m la n d in g is o ff T h e T V s d e g a u s s i n g c irc u it d id n o t d e m a g n e tiz e a p e rtu r e g rill m e t a l s u p p o rt S a m e c o lo r b lo tc h e s re m a in a t th a t a r e a o f th e s c re e n re g ...

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Страница 17: ...is time inspect the bottom area of the picture tube to make sure the ground strap is touching the black aquadag coating 5 Using a small screwdriver or center punch as a puncturing tool seat it into the center of the soft lead anode button cavity hole The puncturing tool must be able to pass through the anode hole and not touch the anode button s outer metal rim 6 Being careful not to hit the glass...

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Страница 19: ...ive when the TV is ON Video Processing The Y C Jungle IC selects a video signal from one of two external video inputs or the internal tuner video for processing Contrast brightness color level and hue are also controlled in this IC A change in level is received by the Micro IC stored in memory and communicated to this Y C Jungle IC thorough the data and clock inputs The final stage within this IC ...

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Страница 21: ...om the converter stage is applied to a trans former in the voltage output stage The transformer s secondary wind ings are used to make the four voltages The most important voltages are the standby 5V and the B voltage In the 13 and 20 BA 4 chas sis the B is 116Vdc In the 27 TV B equals 135Vdc The standby 5V is used to power the microcomputer The B is used to power the horizontal deflection and hig...

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Страница 23: ... wave The operation of the oscillator consists of three parts 1 A quiescent state 2 When the bottom transistor is ON and the top is OFF 3 When the bottom transistor is OFF and the top is ON The Quiescent State The oscillator starts when DC voltage from fusible resistor R606 is ap plied to the oscillator stage Two initial current paths are taken toward ground within the oscillator stage The first c...

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Страница 25: ...nent Input Output T603 pin 4 C614 R608 R609 R608 R609 IC601 2 base Emitter IC601 2 collector Emitter T602 pin 2 Pin 1 T603 pin 6 Both IC601 transistors receive a change in base bias While current is flowing through T602 pins 2 1 a positive voltage is induced and output T6502 pin 3 This is coupled into the base of IC601 2 turning it ON At the same time a negative voltage is induced and output T602 ...

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Страница 27: ... transistor s C E breakdown voltage specification is not exceeded Protection Thermal R606 fusible resistor Oscillator Frequency The oscillator frequency is predominately a function of T603 inductance and C614 capacitance forming a sine wave at the junction Since the inductance of T603 is changed with a load the frequency of the oscilla tor will be different when the set is turned ON O s c illa t o...

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Страница 29: ...odel KV20M40 Converter IC601 2 E AC DC at R606 Vp p Freq B 7 Vac 8 Vdc 20 Vp p 55kHz 22Vdc 11 Vac 11 Vdc 28 Vp p w spikes 49kHz 108Vdc 22 Vac 25 Vdc 35 Vp p 51kHz 116Vdc 40 Vac 50 Vdc 60 Vp p 54kHz 116Vdc 75 Vac 100 Vdc 100 Vp p 61kHz 116Vdc 110 Vac 150 Vdc 150 Vp p 78 5kHz 116Vdc 120 Vac 166 Vdc 170 Vp p 104kHz 116Vdc When beginning to increase the AC voltage to the set under test the AC current ...

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Страница 31: ...27 NOTES ...

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Страница 33: ...Source 12Vdc is applied to several stages at plug in Stage Purpose Q604 Q605 switched 9V regulator Applies 9Vdc to the Jungle IC to power ON the TV RY601 Degaussing Relay Permits the degaussing relay to operate at plug in TV power is OFF Q203 Audio mute Insures audio mute at power OFF IC002 Standby 5Volt regulator Powers and resets Micro IC001 See below IC001 Vcc Power At plug in Micro IC001 is po...

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Страница 35: ...ntains The user s picture and sound preferences The last active TV station information and The TV operating parameters height width linearity OSD position etc Each time the user s preferences and channel are changed the Micro IC001 loads these changes into memory IC003 Micro IC001 and Memory IC003 communications occur during these times Micro Memory Communications When Direction Purpose Plug In To...

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Страница 37: ...symmetrical square This waveform is applied to a tank circuit consisting of C614 and T603 which is resonate at about 60kHz in this TV set The output at T603 is a bell shaped curve shown in the diagram below The oscillator frequency input to this tank circuit is above resonance at point A Therefore the output of T603 is not at maximum By changing the frequency of the oscillator the secondary power ...

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Страница 39: ...ly blooming as the B fluctu ates To avoid this Q602 monitors the ABL voltage from the flyback trans former secondary A bright scene causes this ABL voltage to decrease Q602 inverts this change and a positive going change is applied to the error regulator IC602 pin 1 This results in a reduction of T603 output shifting the operating point away from the top of the bell curve This reestablishes regula...

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Страница 41: ...lugged in This standby 7 5 is regulated down to standby 5V Standby 5 voltage is used to power the Micro and Infrared receiver so it can respond to a power ON command from the user When the Micro receives a power ON command first the degaussing circuitry becomes active While this circuit operates the power relay is energized This relay delivers AC power to the converter stage which outputs B 12Vdc ...

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Страница 43: ...ses Q5001 s cur rent flows from T5001 pin 1 3 through the drain to source of Q5001 thor ough R5011 to ground In itia l C u rre n t P a th to G ro u n d In p u t O u tp u t T 5 0 0 1 S B T P in 1 P in 3 Q 5 0 0 1 D ra in S o u rc e R 5 0 1 1 G ro u n d Current flowing thorough transformer SBT T5001 pins 1 3 induces volt ages into the other windings A positive voltage leaves T5001 pin 4 through C500...

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Страница 45: ...e decreases the power available at the SBT T5001 secondary and the voltage is reduced Current Limiter The current through Q5001 is limited by reducing its gate voltage Since Q5001 and R5011 are in series the current flowing through R5011 rep resents the current in the FET If the current through R5011 drops 0 6Vdc Q5002 begins to conduct Its conduction reduces the FET gate voltage limiting its curr...

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Страница 47: ...43 NOTES ...

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Страница 49: ...ansformer T602 sets the converter frequency The secondary output of the Power Input Transformer T603 is deter mined by the converter frequency input to its primary The converter oscillator waveform is applied to a tank circuit consisting of C614 and T603 which is resonate at about 60kHz in this TV set T603 s output is a bell shaped power curve shown in the diagram The oscillator frequency input to...

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Страница 51: ...nformation from memory 7 Micro Jungle IC Tuner Audio processor Communications Data and clock are used to notify the other ICs to return to the former TV condition at power down Data and clock communications signals are high rise time waveforms with harmonics To avoid communications interference with the picture the microprocessor only communicates with other ICs during the vertical interval time a...

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Страница 53: ...reset After the reset line goes HIGH IC001 can respond to the Power ON command Immediately the degaussing output line at IC001 pin 13 goes HIGH to start degaussing This HIGH is applied to Q601 s base turning the tran sistor ON Current flowing through Q601 also flows through the RY601 relay coil energizing the degaussing relay AC current from the 120Vac line can pass through the relay into the dega...

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Страница 55: ...51 NOTES ...

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Страница 57: ... applied to Q604 and Q605 It remains LOW as long as the set is ON The LOW is applied to the base of switch Q604 turning it OFF With Q604 turned OFF its collector voltage is allowed to rise to the zener voltage of D611 9Vdc The zener voltage comes from pull up resistor R649 connected to the 12 volt source The 9Vdc back at the zener diode s cathode is connected to the base of regulator Q605 The posi...

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Страница 59: ...55 NOTES ...

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Страница 61: ...Memory The user settings stored in memory will include TV station last station used CC channel block favorites Input Selection Video 1 Video 2 or TV input Picture settings Brightness color sharpness etc if not at default level Volume level tone balance speaker ON OFF The waveform of the VTIM signal is shown preceding the IC003 memory data and clock signals TV ON Active channel Channel 1 IC301 pin ...

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Страница 63: ...37 Bi directional Data All waveforms at 5V div Time base 200usec div Channel UP Command This third scope shot shows that additional data and clock are added to the communications line when the channel up was pressed Similar data is present when other buttons such as video selection volume and display are pressed TV ON Remote Channel Up button pressed Channel 1 IC301 pin 5 VTIM Channel 2 IC001 pin ...

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Страница 65: ...Jungle IC These models must be identified to the Jungle IC so it knows to route composite video V out to the filter and receive luminance Y color C information from the filter as a departure from the internal video process ing path Data from the Micro identifies the presence of the external comb filter This data comes from ID codes found in the Micro and memory IC The technician can access them fr...

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Страница 67: ...ulses are input or there will be no OSD IK Sense Circuit The Jungle IC adjusts the levels of each R G and B signal to maintain a level of white balance The current drawn by each picture tube cathode is monitored as long as the TV set is ON The monitoring process results in three pulses that reside in the vertical blanking invisible area of the picture Each pulse corresponds to the three cathodes o...

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Страница 69: ...ts a 1 second positive pulse that is applied to TU101 pin 17 to mute just the audio This insures no audio noise is heard when changing stations The mute output from IC001 pin 5 also goes HIGH when the volume down button is pressed and the level has reached its lowest limit IC001 pin 5 also goes HIGH when the mute button is pressed This is summa rized in the following chart A u d io M u t e fr o m ...

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Страница 71: ...67 NOTES ...

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Страница 73: ...g signals from the Jungle IC301 are applied to IC001 pin 2 Both timing signals are necessary to position the OSD characters on the screen If one were missing there would be no OSD or CC text The OSD characters generated from IC001 pins 50 52 are accompanied by switching signals applied to IC301 pin 29 These switching signals must go HIGH to displace the input video and enable the OSD R G and B tha...

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Страница 75: ...71 NOTES ...

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Страница 77: ...IC701 to be applied to the picture tube cathodes F i n a l P a r t s i n t h e V i d e o O u t p u t S t a g e P a r t L o c a t i o n P u r p o s e Y C J u n g l e I C 3 0 1 M a i n A b o a r d S e p a r a t e s v i d e o i n t o Y C c o m p o n e n t s w h e n t h e r e i s n o e x t e r n a l c o m b f i l t e r U s e s t h e Y B W s i g n a l t o a d j u s t t h e R G B o u t p u t v o l t a g...

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Страница 79: ...owed to pass Color bar pattern on TV screen Digital scope is set for peak waveform presentation The 3 IK pulses are difficult to see in this digital picture but are present to the right of the open vertical area The vertical lines in the waveform represent the horizontal scan lines Channel 1 CN301 pin 4 2v div Channel 2 D301 Cathode 1V div Time base 2msec div The output IK signal is applied to IC3...

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Страница 81: ...o f r e s id u a l h o riz p u ls e s a t th e b o tto m N o rm a l p ix 2 V p p P in s 7 9 N e g p u ls e s B la n k e d P ix 1 8 0 V p p IK p u ls e s N o rm a l P ix 1 8 0 V p p o f R G o r B s ig n a l w ith a 1 2 0 V p p IK n e g p u ls e A m p lify th e 3 2 V p p IK te s t s ig n a l a n d 0 2 V p p h o riz o n t a l s ig n a l to th e p ic tu re tu b e IC 7 0 1 P o s itiv e p u ls e s B la ...

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Страница 83: ... as in the 20 BA 4 chassis A V Switcher Inputs Outputs Inputs Outputs Tuner 1 V 1 is the main picture video to the Jungle IC Tuner 2 optional V 2 is the video signal to the PIP board Video 1 Composite or S Video Video 2 optional Video 3 optional Picture in Picture PIP Board Signal Flow PIP Board Input Outputs Input Output Video 1 from the A V switcher IC Luminance Y R Y V and B Y U PIP insertion s...

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Страница 85: ...signal at connector CN302 12 and 13 2 9V at CN302 1 which becomes 5Vdc on the board 3 Input video signal at CN302 2 2Vp p 4 The P board uses the child pictures sync to sample and store the child picture The main picture s vertical and horizontal pulses are used to determine where the beam is at any given moment so the Picture in Picture can be output for main picture insertion at the proper locati...

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Страница 87: ...ompensate High Voltage Horiz Output Flyback Transformer FBT Makes primary drive signal Develops picture tube accelerating high voltage Makes remainder of tube and vertical output voltages Horiz HP AFC Protection Horiz Output Resistive Voltage Dividers Transistors Jungle IC Micro Compares huge horiz output pulses HP and video sync for AFC lock of H oscillator Excessive B current or FBT voltages are...

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Страница 89: ...signal from IC541 pin 3 is used in the protection circuit This 30Vp p signal from pin 3 is reduced to 5Vp p and monitored by Micro IC001 to prove the vertical stage is working Deflection yoke The deflection yoke translates the electrical current flowing through its coils into a magnetic field that positions the election beam vertically Current flowing through the deflection yoke coil is returned t...

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Страница 91: ...87 NOTES ...

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Страница 93: ...01 The increased current at the secondary is necessary to drive the low gain higher power and horizontal output tran sistor Q502 Horizontal Output Q502 is the output transistor that drives two inductive loads and two circuits The deflection yoke Develops a magnetic field in order to move the electron beam from left to right on the screen The flyback transformer Develops high focus screen and 13Vol...

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Страница 95: ...e FBT and horizontal out put transistor If the current becomes excessive Q571 conducts ground ing out the DC voltage from the Jungle IC301 pin 18 This ground causes IC301 pin 34 to send data to Micro IC001 pin 37 The data instructs IC001 to shut OFF the TV allowing the horizontal output transistor to cool down Automatic Brightness Limiting ABL The purpose of this circuit is to prevent sudden brigh...

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Страница 97: ...Vp p pulse that is reduced by R549 and limited by zener diode D001 to 5Vp p IC001 pin 17 receives and monitors this 5 volt vertical pulse to prove the Vertical stage is operating If IC001 detects a loss of these vertical flyback pulses for two seconds IC001 will turn the TV OFF As part of IC001 s diagnostic program after the set is turned OFF but not unplugged the Timer Standby light will blink fo...

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Страница 99: ...the 3 4Vdc from IC301 pin 18 is grounded out This causes IC301 to send shutdown data from pin 34 to IC001 pin 37 IC001 responds by shutting OFF the TV set when pin 6 is brought HIGH After the TV is shutdown the Timer Standby light blinks two times pauses and repeats for as long as the set is plugged into 120Vac Troubleshooting The self diagnostic part of Micro IC001 causes the Timer Standby light ...

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Страница 101: ...Place your DVM at Q571 collector Turn the TV ON This voltage should not rise above 10Vdc If this voltage is HIGH suspect Q571 R571 and other resistors in the area If these protection parts test OK there is a heavy current demand on the B line The problem may be a short at the FBT secondary wind ings Timer Standby light blinks four times A vertical deflection failure or horizontal drive failure is ...

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Страница 103: ...H The number of times the TV has failed is held in memory As long as there is failure information present the standby light will blink when the set is tuned OFF Unplugging the TV set will clear the memory informa Self Diagnostic On Screen Display A dormant intermittent problem is difficult to detect The BA 4 chassis Control Tuning System IC001 has a program to record the number of times the TV has...

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Страница 105: ...e control Press buttons 8 then press ENTER Self Diagnostic Exit Shutting off power to the set retains the memory information and allows you to return to the TV picture Self Diagnostic Circuit The self diagnostic program is contained in the Control Tuning System IC001 The number of problems is detected by the program is stored in IC001 This number remains in IC001 s resident memory as long as the T...

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Страница 107: ...wo four and five blinking light failures to be stored in memory the Timer Standby light would blink two times pause and repeat when the TV shut down The number of failures has nothing to do with how many times the light blinks Display By using the TV s remote control you can access this failure information stored in memory Once IC001 receives the self diagnostic access com mand at pin 12 IC001 pow...

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