Sony CTV-25R1 Manual
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Sony CTV-25R1 Manual

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Training Manual
®
Color
Television
BA-4 Chassis
Circuit Description and Troubleshooting
Course: CTV-25
R1

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Summary of Contents for Sony CTV-25R1

  • Page 1 Training Manual ® Color Television BA-4 Chassis Circuit Description and Troubleshooting Course: CTV-25...

  • Page 2: Table Of Contents

    Table of Contents Additional Circuits Introduction Power Supply Block - 27” Models The Trinitron Picture Tube ® Standby Power Supply The Trinitron Electron Gun Operation Basic Oscillator The Trinitron Screen Additional Components Picture Tube Defect Symptoms B+ Regulation - 27” TV Picture Tube Handling and Vacuum Disposal Regulation...
  • Page 3 TV Reception Reception from Power ON Channel Change Audio Mute Auto Station Programming Video Inputs Video Output Spot Elimination Circuit Troubleshootintg Video Block - 27” With PIP Picture in Picture (PIP) Board Signal Flow Picture in Picture Processing Deflection Block Vertical Deflection Horizontal Deflection Protection...

  • Page 4: Introduction

    Purpose The purpose of this book is to: • Show through diagrams and explanation how the Sony Trinitron Picture tube now works because it has evolved since inception in 1968. • Provide organized, simplified diagrams that provide an insight to understanding the necessities of the circuit’s operation. This is an essential aid to rapidly determining the cause of a failure.

  • Page 5: The Trinitron

    Red, Green and Blue are the primary colors for light. ney. The outer cathodes are angled slightly to send electrons through In 1968 the Sony Trinitron picture tube was a departure from the tradi- the gun structure. Their final targets are the red and blue phosphor at tional three-gun color picture tube.
  • Page 7 Five Grid Structures 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 The electron gun consists of the cathode and several metal rings called electrons is attracted toward the positive grid two structure, resulting in grids.
  • Page 9 There is no CV control in newer Sony TV sets. The CV control end of the picture tube’s high voltage resistor is grounded so there is still a differ- In a TV, high voltage drops during bright scenes because of heavy cur- ence in convergence plate potiential.

  • Page 11: The Trinitron Screen

    The Trinitron Screen Improvements in deflection yoke construction have compensated for the reduced top/bottom deflection (Y-axis). Along the X-axis, the weaker In front of the electron gun are the: magnetic field causes the picture to look like an hourglass. This is be- •...

  • Page 13: Picture Tube Defect Symptoms

    In diagram 6 you can see the slits have a more important purpose. When Picture Tube Defect Symptoms all three beams are turned ON, the narrow AG slots prevent adjacent Several problems can occur in new picture tubes. The bench technician electron beams from landing on the wrong color phosphor.
  • Page 15 * O n ly th e h e a te r p in s s h o u ld h a v e r e s is t a n c e . A ll o th e r p in s h a v e D e f e c t i v e P ic t u r e T u b e S y m p t o m s in fin ite (∞...

  • Page 17: Picture Tube Handling And Vacuum Disposal

    5. Using a small screwdriver or center punch as a puncturing tool, seat Picture Tube Handling and Vacuum Disposal 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 Once you have determined that the CRT is inoperative, air should be let touch the anode button’s outer metal rim.

  • Page 19: Overall Block Diagram

    the last station viewed and the Jungle IC is instructed to select the last Overall Block Diagram video input used before the set was turned OFF. The communications data and clock lines are always active when the TV A TV set consists of several stages or blocks: is ON.

  • Page 21: Power Supply - 20" Tv & Smaller

    The power output control. Power Supply Block – 20” TV & smaller The purpose of this stage is to maintain/regulate the B+ voltage. The input to the power control stage is the B+ voltage. Variations in the B+ In the smaller BA-4 chassis TVs, power is applied to most of the TV voltage will change the converter’s oscillator frequency.

  • Page 23: Converter

    The Quiescent State Converter The oscillator starts when DC voltage from fusible resistor R606 is ap- plied to the oscillator stage. Two initial current paths are taken toward In the past, the word “converter” referred to a rotating machine consist- ground within the oscillator stage.
  • Page 25 A magnetic field is created when current flows through pins 1-2 of PRT When the collapsing magnetic field in T603 has depleted its energy, the transformer T602. This induces a negative voltage that outputs the trans- cycle repeats, starting with the charging of C614. The result is a square former at T602/pin 3.
  • Page 27 Protection 2 – D690 & D691 Oscillator Frequency The oscillator transistors (IC601) are protected from a base to emitter The oscillator frequency is predominately a function of T603 inductance failure. A transistor’s base to emitter junction can be punctured (open) or and C614 capacitance, forming a sine wave at the junction.
  • Page 29 When beginning to increase the AC voltage to the set under test, the AC What to Expect When Increasing the AC Voltage to the TV current will increase sharply until the B+ reaches the correct voltage for Observe: Normal on a 20” BA-4 chassis TV AC Current (degaussing coil Current will rise to 1 amp at about 12Volts AC, then that set (116Vdc or 135Vdc) and then drops gradually as AC voltage is...
  • Page 31 NOTES...

  • Page 33: Converter Voltage Outputs

    +12 Vdc Source Converter Voltage Outputs +12Vdc is applied to several stages at plug in Stage Purpose Once the converter oscillator is running, current is induced into the sec- Q604, Q605, switched +9V Applies +9Vdc to the Jungle IC to power ON ondary windings to power the set.
  • Page 35 IC001 Memory Data Retrieval After reset, one of IC001’s first programs is to retrieve data from the external EEProm memory IC003. Data and clock are output IC001/pins 36 and 38 to request a reading of all the memory information. The memory information is serially output IC003/pin 5 and stored in Micro IC001’s resident memory (internal RAM).

  • Page 37: B+ Regulation - 13" & 20" Tv

    T603 transformer, including the B+. This regulation method allows the B+ voltage from T603’s secondary winding to be main- Measured using a Sony model KV20M40 TV connected to 120Vac. tained at a constant level. Additional circuits Resistor R699 samples the B+ voltage from PIT T603 and applies it to a voltage divider (R626 and R625).
  • Page 39 through its emitter-base junction, R628 and C625, to ground. Q603 turns ON increasing the voltage at error regulator IC602/pin 1. This results in a decrease in T603 output to offset the no load condition at power OFF. Reduce picture blooming Picture blooming can occur when a bright scene is called for.

  • Page 41: Power Supply Block - 27" Models

    Power Supply Block – 27” Models 13” and 20” Sony Electronics BA-4 chassis In the 13” and 20” Sony Electronics BA-4 chassis TV sets, the converter oscillator runs when the set is plugged in. Only the “Set +9V” is switched ON to turn ON the TV.

  • Page 43: Standby Power Supply

    Current flowing thorough transformer SBT T5001/pins 1-3 induces volt- Standby Power Supply ages into the other windings. A positive voltage leaves T5001/pin 4, through C5004 to Q5001’s gate. This positive voltage keeps the FET This standby power supply is new to the consumer TV line. It contains a ON.

  • Page 45: Additional Components

    When FET Q5001 is turned OFF, its drain voltage rises above the 164Vdc- Additional Components supply voltage (to about +300Vdc). This is because magnetic energy There are several additional components used in this circuit that have stored in the SBT T5001 winding collapses. The reversed current flow not been discussed: applies a positive voltage to charge C5003 via D5003: Additional Components...
  • Page 47 NOTES...

  • Page 49: B+ Regulation - 27" Tv

    Therefore the output of T603 is not at maximum. By changing the fre- B+ Regulation – 27” TV quency of the oscillator, the secondary power output of the PIT T603 can be adjusted to provide sufficient load current while maintaining the same The primary purpose of this stage is to regulate the B+ voltage that out- B+ voltage.

  • Page 51: Power On/Communications Block

    Below is a list of the sequence of operation and their purpose: vertical timing (VTIM) signal from the jungle IC. In previous Sony TV sets, the 60Hz VTIM signal was crucial to the start- Power ON Sequence ing operation of the microprocessor. If there was no VTIM signal into the...

  • Page 53: Degaussing Circuitry

    AC current from the 120Vac line can pass through the relay into the Degaussing Circuitry degaussing coil. The 120Vac input must first pass through several parts before reaching the degaussing coil: Concept Parts between the AC Line and the Degaussing Coil Part Purpose The picture tube has three electron beams that are targeted to exact...
  • Page 55 NOTES...

  • Page 57: Power On

    Power OFF Power ON Additional circuits connected to IC001/pin 6 are used during power OFF to insure proper turn OFF. This is because only the Set +9Vdc is re- Power ON moved at power OFF while the remaining converter voltages are present Once the Micro has received Standby +5Vdc at plug in, the external to many circuits.
  • Page 59 NOTES...

  • Page 61: Communications

    Communications Before normal communications can begin, start-timing pulses are needed. Then Data and Clock (I C) communications will run as long as the set is powered ON. Start Once the TV is powered ON, Set +9Vdc is available to the Y/C Jungle IC301 at pin 44.
  • Page 63 Missing VTIM Timing Signals Unlike previous Sony TV sets, in the BA-4 chassis if the VTIM timing signal from IC301 were missing, data and clock would still output the Micro IC001/pins 36-39 and the set would appear to function normally except there would be no on screen display (OSD).

  • Page 65: Video Processing Block

    Jungle IC so it knows to route the separate Y and C inputs differently. interference and irregularities, as well as separate the Y from the C. Different digital filters are used in different models of Sony TVs. In the 27” screen BA-4 chassis, there maybe an additional video input and video output jack.

  • Page 67: Video Output

    Video Output The video processing continues from within the Y/C Jungle to the picture tube. The Y/C jungle IC takes the composite video or S video and con- verts this information into separate R, G and B voltage levels. These voltages are amplified by the video output stage and applied to the pic- ture tube cathodes.

  • Page 69: Tv Reception

    Channel Change audio mute TV Reception By pressing the channel + or – buttons on the front panel or remote control, IC001 responds with data from pin 37 for the tuner to change a Reception from Power ON station. At the same time, Micro IC001/pin 5 outputs a 1 second positive Station Information pulse that is applied to TU101/pin 17 to mute just the audio.
  • Page 71 NOTES...

  • Page 73: Video Inputs

    OSD and Closed Caption Video Inputs Before the OSD circuit can function within IC001, it needs timing signals. Horizontal pulses from the horizontal output transistor Q502/collector are The Y/C Jungle IC not only performs luminance (Y) and chroma (C) pro- applied to IC001/pin 17.
  • Page 75 NOTES...

  • Page 77: Video Output

    Video Buffers Video Output These three buffer transistors provide current drive to sink the current from IC701. A short in one of these transistors would stop that color (and activate blanking via the IK circuit). An open transistor will cause that The video output stage utilizes the parts listed below to produce and color to go to a high brightness (with retrace lines).

  • Page 79: Spot Elimination Circuit

    When the picture tube warms up and draws current, these three pulses Color bar pattern on TV screen. Digital scope is set for peak waveform all appear next to each other at the common cathode IK pin 5 of IC701. presentation.
  • Page 81 Troubleshooting The IK circuit may keep the set in blanking because: I K S I G N A L P A T H • The picture tube is old and the amplitude of the IK feedback pulses is C o m p o n e n t S ig n a l I n S ig n a l O u t P u r p o s e...

  • Page 83: Video Block - 27" With Pip

    Picture in Picture (PIP) Board Signal Flow Video Block – 27 with PIP PIP Board Input / Outputs An A/V switch to accommodate the second tuner and the Picture in Pic- Input Output ture (PIP) board are the only sections have been added into the 27” BA- Video 1 from the A/V switcher IC Luminance (Y), 4 chassis.

  • Page 85: Picture In Picture Processing

    Processing Picture In Picture Processing The Picture in Picture circuit board needs the following signals to oper- Overview ate. These signals are present all the time when the set is ON, whether the Picture in Picture section is being turned on or not. These signals The purpose of the Picture in Picture circuitry on the small P board is to are: digitally compress the normal 525 line transmitted picture into a small...

  • Page 87: Deflection Block

    Deflection Block There are several sections to a TV’s main horizontal and vertical Deflec- tion stage: Deflection Sections Name Sections Purpose Horizontal Y/C Jungle Horiz. oscillator. Output Drive Horiz. amplifier. Output Horiz. amplifier to drive the horizontal deflection yoke. Pincushion Y/C Jungle (E/W = Hourglass shaped pictures occur in east/west) Pincushion...

  • Page 89: Vertical Deflection

    provide sufficient current to power IC541/pin 6 during retrace time. Di- Vertical Deflection ode D542 blocks this pulse and prevents it from increasing the +13 volt source. The vertical deflection stage consists of: The vertical flyback signal from IC541/pin 3 is used in the protection circuit.
  • Page 91 NOTES...

  • Page 93: Horizontal Deflection

    Horizontal Output Horizontal Deflection Q502 is the output transistor that drives two inductive loads and two circuits: The horizontal deflection stage consists of several sections: • The deflection yoke – Develops a magnetic field in order to move the • Horizontal Oscillator electron beam from left to right on the screen.
  • Page 95 Automatic Brightness Limiting (ABL) Voltage divider R533, R534 and R532 bias this ABL line with a positive voltage that is applied to Jungle IC301/pin 3. A lower ABL voltage de- The purpose of this circuit is to prevent sudden bright scenes from short- creases the level and gain of the RGB waveform.

  • Page 97: Protection

    Vertical Output Failure Protection Pulses from the vertical output IC are monitored for activity by IC001. Two signals are output when the vertical output stage is receiving the The TV’s protection circuitry either blanks the video or turns the TV OFF. drive signal and amplifying.

  • Page 99: Troubleshooting

    Troubleshooting Normal Operating Voltages Component Input Output The self-diagnostic part of Micro IC001 causes the Timer / Standby light D574 120Vp-p at anode 109.2Vdc at cathode to blink, identifying a problem area. This can be used as an aid in trouble- IC521 Pin 6 = 9.7Vdc Pin 7 = 1.34Vdc...
  • Page 101 4. The normal voltage should be less than 0.5Vdc. If it is less than Timer / Standby light – blinks four times 0.5Vdc before the TV turns OFF again, there is a problem in the A vertical deflection failure or horizontal drive failure is indicated. protection circuit at Q300 or IC301.

  • Page 103: Self Diagnostic

    Self-Diagnostic On Screen Display Self Diagnostic A dormant intermittent problem is difficult to detect. The BA-4 chassis Self-Diagnostic is new in the series BA-4 TV chassis. It uses a blinking Control Tuning System IC001 has a program to record the number of light or OSD to notify you if there is a failure caused by the following: times the TV has failed in the first three categories listed above.

  • Page 105: Self-Diagnostic Circuit

    Clearing the Self-Diagnostic Memory Some of the reasons for the failure could be in this checklist. Method Steps Failure Checklist A. Unplug the TV from AC. Removing AC power clears the Times Standby Possible defect memory at any time. Light Blinks B.
  • Page 107 protect itself. The Timer/Standby light blinks two times, pauses and to appear and enable the OSD. Since IC301/pin 29 is an analog input, repeats to indicate the failure. 0Vdc input leaves the main picture at normal brightness. 2Vdc input If flyback (FBT) pulses were abnormally high, perhaps as a result of reduces the picture to half brightness and 5Vdc blanks or mutes the an open resonate capacitor (C508 in this set), the TV would similarly picture.

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