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S
®
Training Manual
Direct View Television
BA-5 Chassis
Models: KV-13FM12 KV-13FM13 KV-13FM14 KV-20FV12 KV-20FS12 KV-24FV12 KV-27FS12 KV-27FS16 KV-27FV16 KV-32FS12 KV-32FS16 KV-20FS12
Circuit Description and Troubleshooting Course: CTV-27
Sony Service Company A Division of Sony Electronics Inc ©1999 All Rights Reserved Printed in U.S.A.
S is a trademark of Sony Electronics
Circuit Description and Troubleshooting:
Models: KV-13FM12
KV-13FM13 KV-13FM14 KV-20FV12 KV-20FS12 KV-24FV12 KV-27FS12 KV-27FS16 KV-27FV16 KV-32FS12 KV-32FS16
Prepared by: National Training Department Sony Service Company A Division of Sony Electronics Inc. Course presented by _____________________________________ Date ___________________________________________________ Student Name ___________________________________________
Table of Contents
Features
Audio Features Video Features Convenience Features Input/Output Feature Glossary
1
1 1 2 2 2
Inrush Current Protection Switching Power Supply
Startup Regulation IC601 Internal Protection Operating the Supply without a Load Troubleshooting
13 15
15 15 17 19 21
Board Descriptions Overall Block
A board MA or MB Boards CA or CB boards VA or VB Boards D Board
3 5
5 5 5 5 5
+135 OCP and H Protect
Latch and Hold Down H Protect +135 Volt OCP
23
23 23 23
Deflection Block
Horizontal Pincushion Vertical Dynamic Focus and Quadra-pole
25
25 25 25 25
Power Supply and Self-Diagnostics
Protection Self Diagnostics
7
7 9
Power ON/Degaussing
AC Input Standby Supply Power ON Degaussing Shutdown
11
11 11 11 11 11
Horizontal Deflection
Troubleshooting
27
27
Vertical Deflection
Troubleshooting
29
29
Video Path 24" and Under
Digital Comb Filter
31
31
Y/C Processing
31
Audio with K Board
Audio Iinputs and Processing Audio Amp
41
41 41
RGB Drive
IK Pulses and Video Blanking Tube Bias Troubleshooting
33
33 33 35
Appendix - Excerpt from CTV-26 Standby Power Supply
Converter Operation Regulation Over Current Protection (OCP) Over Voltage Protection (OVP) Secondary Output Checking Q621
i
i i iii iii iii iii
Video Path 27" and Above
Inputs and Monitor Out Comb Filter Y/C Processing PIP
37
37 37 37 37
Audio without K Board
Audio Amp Volume Control and Muting
39
39 39
1
Features
Overview
The following section discusses the various features for BA-5 models. These features will be separated into four categories: Audio, Video, Convenience and Input/Output. The BA-5 chassis covers the following models:
The following table shows the type of surround sound and audio output power:
Surround KV-13FM12 KV-20FS12 KV-20FV12 KV-24FV12 KV-27FS12 KV-27FS16 KV-27FV16 KV-32FS12 KV-32FS16 N/A N/A Matrix SRS 3D Matrix Matrix SRS 3D Matrix Matrix Power Output 3W 3W x 2 5W x 2 10W x 2 5W x 2 5W x 2 15W x 2 5W x 2 5W x 2
KV-13FM12 KV-13FM13 KV-13FM14 KV-20FS12 KV-20FV12 KV-24FV12
KV-27FS12 KV-27FS16 KV-27FV16 KV-32FS12 KV-32FS16
The 13" models are identical except they are different colors. The FM12 is gray, FM13 is white and the FM14 is blue. These models will have the same features as the FM12 listed in the following section.
Video Features
All models contain the following video features FD Trinitron WEGA TV Dynamic Picture Processor Auto White Balance
· · · All 20" and above models use Velocity Modulation to enhance the picture. All 27" and above use Dynamic Focus, Magnetic Quadra-pole and Trinitone Color Temperature Adjustment circuits. The KV-27FV16 contains a 3D Digital Comb filter to enhance the picture quality. It also has Enhanced 16:9 Mode.
Audio Features
· All models contain the Auto Mute function. Auto Mute mutes the audio when no signal is received. This prevents loud static from being heard when no station is received. The display will also indicate No Signal in the lower left-hand corner. All models are Stereo with Auto SAP except for the 13" inch models. The 13" inch models are mono and contain only one speaker. All 24" and under manuals contain a headphone jack. All "V" models contain the Steady Sound Auto Volume, BBE enhancement and Dynamic Acoustic Chamber (DAC) features.
Auto Pedestal Clamp Vertical Aperture Compensation
· · ·
· Convenience Features
All the BA-5 models contain the following Convenience features: Speed Surf Tuning Advanced On-screen Menu Channel Label Video Label Multi Language Display Favorite Channel or Favorite Preview
· · The KV-20FV12, KV-24FV12 and all 27" and above models have the Preset Program Palette feature. The KV-27FV16, KV-27FS16 and the KV-32FS16 contain 2 tuner PIP. This includes the Freeze Memo feature.
Feature Glossary
Clock Timer (2 events) Sleep Timer (15/30/45/60/90) V Chip Parental Control XDS/Closed Captioning Auto Channel Programming Customer Tilt Control
Auto Mute Mutes the audio output when the tuner receives no signal. This keeps the loud volume from occurring due to static. Auto SAP If activated, Auto SAP automatically switches to the SAP audio if SAP audio is present. BBE Audio Enhancement Shifts the phase of the audio signal to improve TV sound. Dynamic Acoustic Chamber (DAC) A speaker enclosure that uses the cabinet to improve sound quality. SRS 3D A digital signal-processing algorithm that simulates surround sound using only two speakers. Dynamic Focus Automatically adjusts the focus to improve focus on certain parts of the screen. Magnetic Quadra-pole Controls the electron beam magnetically to enhance picture resolution. Trinitone Color Temperature Adjustment Enables the user to adjust the color temperature to warmer or cooler to match the program. Enhanced 16:9 Mode - This mode uses vertical compression to enhance "anamorphic" widescreen video from DVDs. Advanced On Screen Menu A new colorful On-Screen Menu that is more intuitive and easier to use. Preset Program Palette Picture types that are preset. These include Vivid, Standard, Sports and Movie. Freeze Memo Allows you to save an item on the screen in the PIP window while the main picture continues in real time. Y/Pb/Pr - Delivers optimum picture quality by supplying separate connections for luminance (Y), blue color difference (P B ) and red color difference (P R ). Ideal for DVD players and Digital Television (DTV) set top receiver/decoders. Speed Surf Tuning Allows faster channel scanning when you hold down the Channel Up/Down buttons.
Input/Output
S Video * KV-13FM12 KV-20FS12 KV-20FV12 KV-24FV12 KV-27FS12 KV-27FS16 KV-27FV16 KV-32FS12 KV-32FS16 * Rear/Front · The KV-27FV16 contains a Monitor Out jack. -/-/1/1/1/1/1/1 1/1/Y/Pb/Pr N/A N/A N/A N/A 1 1 1 1 1 Composite * -/1/1 1/1 1/1 2/1 2/1 2/1 2/1 2/1 Fix/Var. Out N/A N/A Yes Yes Yes Yes Yes Yes Yes
2
3
Board Descriptions
24" and Under
Board Name A K CB MB Description Power Supply, A/V Inputs, DGC, Tuner, Pincushion, H Deflection, V Deflection, Audio Amp, Switches, LEDs Audio Processor and SRS Processor CRT Drive and N/S Amp Syscon, Y/C Jungle, Comb Filter,
27" and Over
Description A Power Supply, A/V Inputs, DGC, Tuner, Pincushion, H Deflection, V Deflection, Audio Amp K Audio Processor and SRS Processor CA CRT Drive and N/S Amp MA Syscon, Y/C Jungle, Comb Filter, Sub tuner D Dynamic Focus and Quadrapole Focus HA* Front A/V Inputs and Menu Switches HB* IR detector HX All Switches except KV27FV16 B Board* 3D Comb Filter, P Board PIP Processing VA Velocity Modulation and Quadrapole *Found in KV27FV16 only. Board Name
The differences in layout between the 24" and below and the 27" and above models are the addition of the B, P and D boards for the added circuits. The switches, IR detector and front video input have been moved from the A board to the H boards due to the increased cabinet size.
CB Board
B board CA board
VB board
VA board D board
MB board A board K board (KV-20FV12 & KV-24FV12 only)
P board K board 27 Inch and Over (KV-27FV16 pictured) A board
24 Inch and Under
4
5
Overall Block
Overview
The BA-5 chassis is new for the 2000 model year. It is the first of the BA type chassis to cover 13" to 32" models using the FD Trinitron tubes. In order to accomplish this, parts common to all models are on one board, the A board. The MA or MB board contain the video processing and Syscon sections. If the set contains surround sound audio then it will have a K board. CA or CB boards contain the CRT Drive and Velocity Modulation. All 27" and above models contain a D board. Some 27" and above sets contain P and B boards which plug into the MB board. These boards are for PIP and a 3D Digital Comb Filter.
Deflection
The horizontal, vertical and pincushion correction circuits are contained on the A board. These circuits control the current through the yokes in order to correctly scan the CRT. The FBT produces supply voltages for the vertical output and creates high voltage, focus voltage and G2 screen voltage. Pulses are monitored by the H protect circuit. If these pulses become too large, they will activate the latch circuit which will shut down the supply.
MA or MB Boards
The MA AND MB boards contain the YCJ and System Control circuits. The MB board will be used on all 24" and under sets. All 27" and larger sets will use the MA board. These boards use different YCJ and System Control ICs. The different YCJ allows for more inputs and also controls video switching in the larger sets. In addition, the larger sets contain a different System Control IC that is utilized to produce a better OSD and menu system. In models that have the PIP function, a 2nd Tuner and a P board will be added to the MA board. The P board creates the sub picture using the video from the 2nd tuner. The KV27FV16 contains a 3D Comb Filter that resides on the B board. The B board plugs into the MA board similarly to the P board.
A Board
Power Supply
The A board contains sections that are common to all models. It contains the standby and switching power supplies. The Standby supply is an Energy Star complaint switching supply. It produces 7.5 volts to be used by the MA AND MB board. The MA AND MB board contains a 5V Regulator to power the System Control IC. The main switching supply produces +135 volts, Audio B+ and low voltage supplies. The low voltage supplies are +12, +9 and +5 volts. The A board contains a degaussing circuit which is activated by the DGC line from System Control. This line controls a relay, which when activated, supplies 120 VAC to the degaussing coil.
CA or CB Boards
All 24" and under sets will contain the CB board. The CB board includes the CRT Drive and North/South Drive for tilt correction. The similar CA board will be used on all 27" and over models.
Audio
The audio section on the A board contains the audio output amplifier. There may also be a switching IC that selects the correct audio input if the unit does not contain a K board. Any unit that features surround sound audio or SRS will have a K board.
VA or VB Boards (Not shown)
All sets contain a VA or VB board, which contains VM Drive.
D Board (Not shown)
Larger sets will contain a D board. This board contains Quadra-pole and Dynamic Focus circuits necessary to produce a better picture on larger screen size models.
Video
The A board contains front and rear input jacks and the main tuner. 24" inch and under sets will have a video input select switch on the A board. In other models, the video switching will be handled by the YCJ on the MA board.
A BOARD YUV Y/C A/V INPUTS CV & MAIN TUNER L R L AUDIO AMP. VIDEO SWITCH
PIP P BOARD RGB HP HD Y/C/J E/W PIN H. DEFLECTION
CA OR CB BOARD VIDEO AMP. 200V
RGB CRT H. YOKE
FBT
HV +12V AUDIO SW. OR K BOARD VD CV Y C SUB TUNER I PROTECT COMB FILTER OR B BOARD 7.5V 5V REG. RESET DGC MA or MB BOARD 5V P ON SYSTEM CONTROL H. PROTECT. & OCP V. DEFLECTION -15V V. YOKE
R STANDBY POWER SUPPLY
DGC
+135V
12V
9V
MAIN POWER SUPPLY
+135V AUDIO B+
OVERALL BLOCK 6
14CTV27 1231
4/24/00
7
Power Supply and Self-Diagnostics
Power Supply
When the unit is first plugged in, power is applied through the AC In block to the Standby Supply. The Standby Supply powers the System Control IC, EEPROM, remote sensor and reset circuits. If a Power ON command is received after reset, the System Control IC outputs voltages to turn ON the Power and Degauss relays. When operating correctly, the following can be observed in sequence: · · The power relay clicks; One second later the degauss relay clicks and the hum of the DGC is heard for about two seconds; and · The degauss relay clicks again two seconds later and then a picture is displayed. This entire sequence occurs in the first 5-10 seconds the unit is powered ON. During this time, the Standby/Timer LED will be flashing approximately once per second. The main power supply in the BA-5 chassis uses one switching IC to control switching of the B+ through a transformer. The transformer primary couples the signal to the secondary. The secondary signals are used to create three DC voltages, which are used to supply power to the rest of the set. Feedback from the primary side of the transformer and the +135 volt line created by the secondary are used to control the switching frequency. The IC also has three built-in protection circuits. They are for over voltage, over current and thermal protection. These protection circuits will be covered in the Switching Power Supply section.
Protection
Protection circuits are included to deactivate the set if the following failures occur: Standby +7.5 volt OVP If over voltage occurs on this line, a LOW will be output to the base of the relay drive transistor. This shuts the set OFF. +135 volt OCP This sensor monitors the voltage across a resistor that feeds the H Out and FBT and protects against +135 volt OCP. When OCP is detected, the protect latch is activated. When the latch is activated, drive to the relay is stopped. This shuts down the main power supply. A signal is also sent to the Syscon IC to be used by the SelfDiagnostics. H Protect Or hold down is used to keep the picture tube from emitting harmful x-rays if a failure should occur that causes the High Voltage to rise. When this circuit is activated, it also turns the latch ON. This turns drive to the power relay OFF and sends a signal to the Syscon to be used for self-diagnostics. AKB Protect Or IK protect causes the video to be blanked if the YCJ does not receive the correct feedback from the IK line. The IK line's voltage is representative of the amount of current being drawn by the tube. This current is monitored during vertical blanking. The YCJ outputs one H line for each color and monitors the returning IK voltage. If this voltage is not within the correct operating window, the YCJ alerts the Syscon IC via the I²C bus for use by the Self-Diagnostics. I Protect- I protect occurs when the Vertical Output IC does not return samples of its pump-up pulse to the Syscon. When these pulses are missing, it is an indicator that the vertical section is not working. The Syscon IC monitors these pulses for Self-Diagnostics and protection purposes. When the pulses are missing, the main power supply is turned OFF and Self-Diagnostics are activated.
IC502 VERTICAL OUTPUT STANDBY +5v REG
MA/MB BOARD
I PROTECT
STANDBY SUPPLY
STANDBY 7.5
CA/CB BOARD IC1001 SYSCON DGC STANDBY/ TIMER LED OVP RELAY LATCH HLDWN IC501 + AUDIO SWITCHING SUPPLY A BOARD +135V LV SUPPLY OCP HV DETECT FROM FBT +135 I2C IK IC1702 RGB DRIVE
YCJ
DGC AC IN DEGAUSS
STANDBY +5V
POWER ON RY602
POWER SUPPLY AND SELF-DIAGNOSTICS BLOCK 8
4CTV27
4/25/00
9
Self Diagnostics
The table below shows the number of times the Standby/Timer LED flashes in sequence before pausing and repeating. The table indicates what will happen when failures occur while the set is operating.
Standby / Timer LED Diagnosis Symptom Shutdown. Shutdown.
The set will usually act differently from what is shown in the table when it is powered up with a defect present. However indications will still be given that can guide you in troubleshooting. In the case of intermittent problems, you can check the failure status history by pressing the Display, 5, Vol. and Power buttons. You will see a menu that indicates how many times each item has failed. The failure information is stored in the EEPROM.
Standby/Timer LED Blinks 2 times, pauses and repeats. 4 times, pauses and repeats.
Problem
B+ OCP or H Protect Vertical Failure (may also be Horizontal Failure or Power Supply since loss of either will cause no vertical.) White balance failure, weak picture tube or Low G2 voltage. No reply from Y/C Jungle IC (data bus is busy, grounded or held HIGH) or IK video path is defective at turn ON.
5 times, pauses and repeats. Continues to blink once a second.
1. No video 2. Sound OK. No or defective Y/C Jungle IC301 communications.
IC502 VERTICAL OUTPUT STANDBY +5v REG
MA/MB BOARD
I PROTECT
STANDBY SUPPLY
STANDBY 7.5
CA/CB BOARD IC1001 SYSCON DGC STANDBY/ TIMER LED OVP RELAY LATCH HLDWN IC501 + AUDIO SWITCHING SUPPLY A BOARD +135V LV SUPPLY OCP HV DETECT FROM FBT +135 I2C IK IC1702 RGB DRIVE
YCJ
DGC AC IN DEGAUSS
STANDBY +5V
POWER ON RY602
POWER SUPPLY AND SELF-DIAGNOSTICS BLOCK 10
4CTV27
4/25/00
11
Power ON/Degaussing
Overview
The Power ON/Degaussing circuit shown also includes the AC input and Reset circuits. When the unit is first plugged in, power is applied to the line filter to the Standby Supply. The Standby Supply powers the System Control IC, EEPROM, remote sensor and reset circuits. After reset, if a Power ON command is received, the System control IC outputs voltages to turn ON the Power and Degauss relays. When operating correctly, the following can be observed in sequence: the power relay clicks, one second later the degauss relay clicks, the hum of the DGC is heard for about two seconds, the degauss relay clicks again two seconds later and then finally a picture is displayed. This entire sequence occurs within the first 5-10 seconds the unit is powered ON.
ing instructions. One of its first tasks is to read and load the contents of the external NVM into the registers of IC1001 via the I²C bus. The data in the NVM contains the service data as well as any data relating to customer control settings such as volume level.
Power ON
When the Power On command is received from the Power Switch or the remote control, IC1001/8 Relay goes LOW. This LOW is sent to the A board via pin 7 of CN1004 and CN2002. It is then applied to Q604/B, turning Q604 OFF. When Q604 is OFF, the Standby 7.5 volts is applied to the base of Q607 through R661 and R630. This turns Q607 ON and allows current to flow through RY602, which causes the contacts in RY602 to close. When the contacts close, AC is applied to D605 Bridge Rectifier. This allows the Switching Supply to begin to operate. When the switching supply is operating, the set should be ON.
AC Input
The AC is input to the A board through CN602. The Hi side of the AC line passes through T602/1 and 2, and R605 and R606. These resistors are inrush current limiters. They will be replaced with jumpers in all 24" and above models. The Lo side of the line passes through T602/4 and 3. After this occurs, AC is applied to the following three circuits. They are the Standby Power Supply, the Main Switching Supply and the Degaussing Circuit.
Degaussing
About one second after the Power Relay is closed, the Degauss Relay is closed. This occurs because IC1001/13 outputs a HIGH, which is sent to the A board via pin 6 of CN1004 and CN2002. It is then applied to Q609/ B. This turns Q609 ON, allowing current to flow through RY601 Degauss Relay. This closes the contacts of RY601 and allows current to flow through THP601 and the DGC. This action is accompanied by the sound of the DGC humming. Current flows through the DGC until THP601 becomes warm. THP601 is a thermistor and its resistance increases rapidly as its temperature increases. Its resistance will increase so much that after about two-three seconds, current flowing through the DGC will be greatly reduced. After about five seconds, IC1001/13 DGC goes LOW and the Degauss Relay is turned OFF.
Standby Supply
The Standby Supply is similar to the one used in the AA2W chassis. There is an excerpt from CTV-26 included in the Appendix. Keep in mind that the circuit is the same functionally, but the component identities will be different. When AC is applied to the Standby Power Supply circuit, it begins to operate and outputs 7.5 VDC. This Standby 7.5 volts is applied to the MB board via pin 3 of CN2002 and CN1004. This voltage is input to IC1305/4. IC1305 is a 5V Regulator that also outputs the 5 volts to be used for reset. The Standby 5 voltage is output IC1305/5 to IC1001/27 Vcc. The reset 5 volts is output IC1305/2 to IC1001/30 Reset through a RC network. This RC network provides the delay necessary for Reset to occur. After Reset occurs, IC1001 Control Tuning System begins execut-
Shutdown
The outputs from the Latch and the Standby 7.5 volt over voltage protection circuit are connected to either side of R630. If either circuit goes low, the power relay will turn OFF. The LOW from the latch circuit will also be applied to the HLDWN line, which is input to IC1001/35 for use by SelfDiagnostics.
CN602
2 1
F601 VDR 601
4
A BOARD R613 C655
*REPLACED BY JUMPERS IN 24" AND ABOVE MODELS CN601 THP601 C648 DGC L605 RY601
2 1
1
T602
3 2
R605* R606* C648
Q609 R635 R636 R634 D601 TO CONVERTER BRIDGE RECTIFIER D605 R607 STANDBY 7.5V +12V
STANDBY POWER SUPPLY
STANDBY 7.5V H=DGC R663 R661 R630 Q604
RY602 Q607
STANDBY 7.5V 3
3
CN2002
6 6 7 7
R642
CN1004
4 13 8
L=ON R1048 DGC
MB BOARD R508
D612 MTZJT 77-10D
D602 C601
R1047 IC1305 5V REG. BA3993
2
C1048
5
C1049 C1050
RELAY IC1001 HOLD DGC CONTROL DOWN 35 RESET TUNING SYSTEM VCC 27 M37273MF-258
30 14 12
LATCH FROM Q507/E C602 R653 STANDBY 7.5V OVP FROM Q608/C
FROM POWER SW. FROM REMOTE SENSOR
POWER ON RMCN
SCL 39 SDA 37
I2C
POWER ON/DEGAUSSING 12
2CTV27 1228
4/25/00
13
Inrush Current Protection
Overview
Sets with 20-inch tubes and below use R605 and R606 (shown in the Power ON/Degaussing section) for inrush current protection. Since more current is drawn when a set with a bigger CRT is turned ON, an alternate inrush current circuit is used for sets with 24 inch and larger CRTs. The resistors in smaller sets remain in place after turn ON. The larger sets use a resistor that is shunted by an SCR shortly after power ON. This allows more current to be drawn without dissipating more power.
D603 is a 33 volt zener used for protection. It is not activated during initial turn ON because C609 needs to charge. C609 is a 100-uf capacitor. C609 will not charge to a level of 33 volts before D606 turns ON. This keeps the circuit from activating at power ON. In the event that there is a problem such as D606 opening during operation, C609 will charge and D603 will turn ON. When D603 turns ON, current flows through D607 and R619. This causes Q602 and Q603 to turn ON. When Q603 turns ON, the VIN voltage from C620 is applied to IC601/1 through R644. This causes IC601 to activate its own OCP circuit, stopping the supply from switching. If a failure of this nature were to occur for a very short time, less than four seconds, the supply could restart itself. If the failure lasted longer, a sequence of four flashing Standby/ Timer LED followed by a pause would occur and the Power Relay would be opened. The Standby/Timer LED will continue to flash in the above sequence until power is removed from the set. This removes power from the supply and it ceases to function. This is an indication that there is a vertical failure when actually there is a problem in the power supply.
80 volts 20 volts R621 .6 volts Q601/B 14 volts D606/G Inrush Timing Diagram
In Rush Current Protection
RY602 is closed when the set is turned ON. This applies AC to D605 Bridge Rectifier and R637. D605 Bridge Rectifier supplies DC to the switching supply through R626. R621 is added in order to keep excessive current from being drawn by the switching supply at initial turn ON. R621 is placed in series between the negative terminal of D605 Bridge Rectifier and hot ground. This resistor is not in place in smaller sets that contain R605 and R606. The negative terminal of D605 Bridge Rectifier is connected directly to hot ground in these sets. D606 is a thyristor that is connected across R621. When the set is turned ON, 80 volts is developed across R621. This initial voltage causes D608 to conduct since its zener voltage is 20 volts. When D608 is conducting, Q601 is ON. Q601 keeps C610 from charging when it is ON. As the initial inrush current begins to dissipate, the voltage across R621 decreases. When this voltage drops below 20 volts, D608 turns OFF, causing Q601 to turn OFF. When Q601 turns OFF, C610 begins to charge. When the charge of C610, a 10-uf capacitor, reaches about 14 volts, D606 begins to conduct. After this occurs, the voltage drop across R621 becomes only a few tenths of a volt.
REGULATION FROM IC602/2 +135V
PH601 PC123FY2 PHOTO COUPLER
1 2 3
SWITCHING B+ TO T603/5 PRT TO R637 SWITCHING SUPPLY AC HI FROM RY602 AC LO FROM T602/3 R605 R606 D605
R645
PH601 PC123FY2
4
VIN FROM C620
R649 R626 C614 R651 Q602 R627 C612 R628 R625 C613 Q603 R644 TO REGULATION IC601/1 OCP/FB
D606 R621
R624 R623 Q601 R622 C610 D608 MTZJ-T77-20B D603 MTZJ-T77-33B
D607 R619
C609
R618 A BOARD
INRUSH CURRENT PROTECTION (24" AND ABOVE) 14
3CTV27 1224
4/24/00
15
Switching Power Supply
Overview
The power supply in the BA-5 chassis uses one switching IC to control switching of the B+ through a transformer. The transformer primary couples the signal to the secondary. The secondary signals are used to create three DC voltages that are used to supply power to the rest of the set. Feedback from the primary side of the transformer and the +135 volt line created by the secondary is used to control the switching frequency. The IC also has three built-in protection circuits.
This switching ON and OFF of the internal FET, whose Drain and Source are IC601/3 and 2 respectively, produces a signal output at T603/7 that is rectified by D613 and applied to IC601/4 VIN. The DC voltage produced by D613 is used to sustain the input voltage at IC601/4 VIN. When this sustaining voltage is missing, IC601 will begin to start up. Without this voltage, C620 will discharge on the negative half cycle of the incoming AC. This causes the IC601 to be constantly turned ON and OFF. A chirping noise accompanies this failure and the Standby/Timer LED will flash. If the voltage supplied to IC601/4 VIN exceeds 22 volts, the IC will go into internal over voltage shutdown and cease oscillation.
Startup
When power is turned ON, RY602 is closed and AC is applied to R637 and D605. The AC applied to R637 is passed through R662 and R660, and applied to IC601/4 VIN. As C620 charges on the first positive half cycle of the incoming AC signal, its voltage reaches the threshold at which IC601 Converter will start to operate. This threshold is around 11 volts. Once IC601 starts operating, the incoming AC will not be a factor in sustaining the charge of C620. The voltage at IC601/4 VIN will remain at approximately 17 VDC during normal operation due to a sustaining voltage, which will be created using the signal from T603/7. When AC is applied to D605, 144 VDC is developed. This voltage is sent through R626 to T603/5. When the voltage across C620 is sufficient to allow IC601 to operate, current flows through T603/5 and T603/4, and T603/3 and T603/2, through IC601/3 D and IC601/2 S, and finally through R632 and R641 to ground. IC601/3 and 4 are the Drain and Source for an internal FET. The gate of this internal FET is connected to an oscillator contained in IC601 Converter. When the voltage threshold for startup is reached at IC601/4 VIN, the oscillator begins operation by outputting its positive half cycle. This turns the internal FET ON, allowing current to flow as described above. When the oscillator starts its negative half cycle, the FET is turned OFF and current stops flowing through T603/4 and 5 and T603/2 and 3.
Regulation
IC601 Converter is used here in quasi-resonant operation. Quasi-resonant refers to the fact that there are two different levels used to determine how long the internal FET of IC601 should be turned ON or OFF. The resistance and capacitance values of the components associated with IC601/1 and 2 determine this. When the supply is started, the voltage created across R632 and R641 monitors the current through the internal FET. This voltage is fed to IC601/ 1 through R633. This pin is connected internally to two internal comparators. When this voltage reaches .73 volts, Comparator 1 in IC601 Converter turns the internal FET OFF. When this occurs, a positive going signal is produced at T603/7 due to the collapsing magnetic field. This signal is rectified by D614. The rectified voltage is delayed by the charging action of C652. The delay time is a factor of the values of R646, R643 and C652. The rectified and delayed voltage from D614 is then sent through D611, blocking diode, to IC601/1 OCP/FB. When this voltage reaches approximately 4 volts, Comparator 2 in IC601 turns the FET ON. This causes a loss of the D614 voltage due to the changes in magnetic field of T605. The voltage across R632 and R641 will increase again and the cycle repeats itself.
A BOARD
IC601 STR F6624/6654 CONVERTER VIN OCP/FB D GND S
3 5 2 4 1
123.7 VDC R645
R644 R637 R662 R660 D613 D614 R646
C620
R633
D611
FROM +135 3 2 ERROR PH601 FROM PC123FY2 IC602/2 122.8 VDC IN RUSH *Q603 CURRENT PROTECT FROM Q602 R638
4 1
T603 R632 D610 R641 C619 R643 C652
7 8 12 14 11
CREATES AUDIO B+ CREATES LOW B+ CREATES +135
AC HI FROM RY602
C617 C645 D605 C647 R627
5
13 2 17
C646 R626
3 4
AC LO FROM T602/3
C644
C612
16
R628 R621*
TO IN-RUSH CURRENT LIMIT/PROTECT
*ONLY FOUND IN 24" AND ABOVE MODELS. SEE IN RUSH CURRENT PROTECTION
SWITCHING POWER SUPPLY 16
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17
FET ON
~ 4 VOLTS ~
FDBK OSC.
LATCH
FET OFF TRANSIENT
~ .73 ~
DC LEVEL CONTROLLED BY PH601
UVLO OVP TSD Vin OVER-CURRENT 1 & FEEDBACK SOURCE 2 DRAIN 3 SUPPLY 4
IC601/1 PH601 is an opto-isolator. Pins 1 and 2 are connected to the +135 volt line and to IC602/2 Error Amp. These pins are the terminals of an LED. Variations in the +135 volt line effect how much light is output from the LED. Pins 3 and 4 of PH601 are the emitter and collector of the internal phototransistor. The brighter the light from the LED, the more current can flow through the C-E junction. When there is conduction, C-E voltage from IC601/4 VIN is applied to IC601/1 OCP/FB through R644. This DC voltage helps regulate the supply by changing the DC level of the signal created by the quasi-resonant operation. Changing the DC level alters the ON/OFF time of the internal FET. This in turn changes the frequency of operation. By controlling the frequency, the power transfer is controlled between the primary and secondary windings of T603. This regulates the supply's output, which means regulation is maintained by frequency control.
The table below shows the typical operating frequency checked at IC601/ 3, and the IC601/1 voltage under maximum (white raster) and minimum (black raster) loads.
+135 White Raster Black Raster 135.6 DCV 136 DCV Frequency 145kHz 200kHz IC601/1 DC Voltage 1.71 VDC 1.6 VDC
OCP
IC601
IC601 Internal Protection
IC601 has three protection circuits. They are over voltage, over current and thermal protection.
OVP
The over voltage protection circuit functions by monitoring the voltage present at IC601/4 VIN. If this voltage rises above 22.5 volts, the switching circuit will be stopped. This OVP activates a latch circuit and power must be disconnected for operation to restart.
OCP
Over current protection is done by monitoring the voltage at IC601/1 OCP/ FB. IC601/1 OCP/FB only operates during the turn ON portion of the FET switching. If the voltage passes over the threshold during this time, switching will stop. This will cause the voltage at IC601/4 VIN to fall below the voltage needed to operate the IC. This voltage will rise above the operating threshold on the next positive half cycle of the AC input and cause the FET in IC601 to turn ON. If OCP is detected again by IC601/1, the cycle
GROUND 5
A BOARD
IC601 STR F6624/6654 CONVERTER VIN OCP/FB D GND S
3 5 2 4 1
123.7 VDC R645
R644 R637 R662 R660 D613 D614 R646
C620
R633
D611
FROM +135 3 2 ERROR PH601 FROM PC123FY2 IC602/2 122.8 VDC IN RUSH *Q603 CURRENT PROTECT FROM Q602 R638
4 1
T603 R632 D610 R641 C619 R643 C652
7 8 12 14 11
CREATES AUDIO B+ CREATES LOW B+ CREATES +135
AC HI FROM RY602
C617 C645 D605 C647 R627
5
13 2 17
C646 R626
3 4
AC LO FROM T602/3
C644
C612
16
R628 R621*
TO IN-RUSH CURRENT LIMIT/PROTECT
*ONLY FOUND IN 24" AND ABOVE MODELS. SEE IN RUSH CURRENT PROTECTION
SWITCHING POWER SUPPLY 18
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19
will repeat. Every time this cycle repeats, a chirping sound can be heard from the power supply. This chirp occurs when the VIN voltage rises again to a voltage at which IC601 can operate. This chirping sound is made each time the supply begins to restart. It will continue to repeat until the Syscon IC senses a vertical failure. At that time the power relay will be turned OFF and the Standby/Timer LED will flash in sequences of four. You should also note that under the above conditions the +135 volt output at L603 remained at 136 volts throughout. The signal seen at IC603/3 started as sine waves clipped at the negative peaks and gradually came to look more like a normal sine wave as the input voltage was increased. The frequency of this signal ranged from 236 kHz at 40 VAC to 320 kHz at 120 VAC.
An example of this failure would be a short on the 135-volt line such as VM Output short. This type of failure would not be associated with a Horizontal failure such as H Out, 200volt short (Video Amp) or FBT. That circuit contains another OCP that would cause the Standby Timer LED to flash in sequences of two. This will be discussed later. Thermal
The thermal shutdown works by sensing the temperature of the lead frame that the IC is mounted to internally. The semiconductor wafer is mounted to a lead frame to dissipate heat. When the temperature of the frame reaches 140 degrees Celsius, the latch is activated. Power must be disconnected for operation to restart.
D614/K 2v 5us IC601/3 100v 5us
Operating the Supply without a Load
It is important to be able to isolate whether a problem is in the power supply or other circuitry. This supply can be run unloaded at AC input voltages ranging from 30VAC to 120VAC. You can unload the supply by unsoldering one side or removing L603. After removing L603, place a jumper across the contacts of RY602. Plug the set into a variac and begin to slowly bring up the AC voltage. At about 30 volts, the supply will begin to operate. The following table shows the state of several points at various AC input voltages:
IC601/1 40VAC 60VAC 80VAC 100VAC 120VAC .87 VDC .98 VDC 1.11 VDC 1.21 VDC 1.22 VDC IC601/3 160 Vpp 200 Vpp 230 Vpp 260 Vpp 280 Vpp IC601/4 12 VDC 12.83 VDC 13.2 VDC 13.5 VDC 13.9 VDC Switching B+ 51 VDC 79 VDC 106 VDC 134 VDC 163 VDC
IC601/1 1v 5us
T603/7 10v 5us
IC601/2 1v 5us
A BOARD
IC601 STR F6624/6654 CONVERTER VIN OCP/FB D GND S
3 5 2 4 1
123.7 VDC R645
R644 R637 R662 R660 D613 D614 R646
C620
R633
D611
FROM +135 3 2 ERROR PH601 FROM PC123FY2 IC602/2 122.8 VDC IN RUSH *Q603 CURRENT PROTECT FROM Q602 R638
4 1
T603 R632 D610 R641 C619 R643 C652
7 8 12 14 11
CREATES AUDIO B+ CREATES LOW B+ CREATES +135
AC HI FROM RY602
C617 C645 D605 C647 R627
5
13 2 17
C646 R626
3 4
AC LO FROM T602/3
C644
C612
16
R628 R621*
TO IN-RUSH CURRENT LIMIT/PROTECT
*ONLY FOUND IN 24" AND ABOVE MODELS. SEE IN RUSH CURRENT PROTECTION
SWITCHING POWER SUPPLY 20
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Troubleshooting
The following table is a list of symptoms that occur when any of the supply voltages are shorted to ground at turn ON. This may be helpful in troubleshooting. It is important that you take into account all the symptoms to aid in your troubleshooting,
Voltage +135 Relay Clicks 2 power On and Shutdown. Power supply chirps. 2 power On and Shutdown. Power supply chirps. 4 clicks. Power ON, Degauss ON and OFF and Shutdown. 4 clicks. Power ON, Degauss ON and OFF and Shutdown. Video No Audio No Timer LED 4 HV No Power Switch Set ON and symptom repeats Set ON and symptom repeats Set ON and symptom repeats Set ON and symptom repeats Suspect Q502, 200 volt problem, T503 FBT IC603 9 Volt Regulator, IC501 Pin and OCP IC604 5 Volt Regulator, Data problem IC603 9 Volt Regulator, IC1301 YCJ or IC301 Depending on model
+12
No
No
4
No
+5
No
No
4
No
+9
No
No
4 the No fourth flash stays on for several seconds. Normal Yes
Audio B+
3 Normal
Yes
No
Set turns OFF
PS401, 402 and IC401, 402 depending on model Q502, 200 volt problem, T503 FBT IC502 V Out, R550 IC502 V Out, R549
+200
2 power On and Shutdown. Power supply chirps.
No
No
4
No
Set ON and symptom repeats Set ON and symptom repeats Set ON and symptom repeats
+12 Scan 4 Normal 3 then fourth for shutdown. Derived -15 4 Normal 3 then fourth for shutdown.
No No
Yes Yes
4 4
Yes Yes
NOTES
22
23
+135 OCP and H Protect
Overview
The +135 OCP and H Protect detection circuits output a HIGH to indicate a problem. These HIGHS are input to the latch circuit that then places a LOW at the base of the relay drive transistor. This eliminates the current path necessary to keep the unit ON. When there is a failure, a signal is also sent to IC1001, which will indicate these failures by flashing the Standby/Timer LED in sequences of two.
greater than that at IC501/6. This would cause IC501/7 to output a HIGH. This HIGH voltage activates the Latch. Note: This is a departure from the way previous models have worked. Typically when the H protect circuit was activated, it turned ON a transistor that grounded the HP input to the YCJ. In turn, the YCJ would disable HD.
+135 Volt OCP
Over current is detected by monitoring the voltage across R556 and R553. When this voltage, which rises as more current is drawn, gets to a level that causes Q505 to turn ON, the latch will be activated. C534 prevents premature triggering of OCP. Three main components generally cause this type of failure. They are T505 FBT, Q502 H Out and the CRT Drive (not shown). You should check Q502 with an ohmmeter first. This component usually fails with a C-E short. Unloading each of them from the circuit one at a time can eliminate these components. Note: Before doing this, ensure that SW501 H Centering Switch is in the center position. Damage will occur to the set if it is not. · Unplug the unit. Start with the easiest by unplugging CN502 from the A board and reapplying power. If the symptom changes from sequences of two flashes to sequences of five flashes, replace IC702 CRT Drive on the C board. · If the symptom remains, unplug the set, reconnect CN502 and remove Q502. Re-apply power. If the symptom changes from sequences of two flashes to sequences of four flashes, replace Q502. · If the symptom remains, unplug the set and remove L510 and R568. These points were chosen because they do not have eyelets. Consequently they are easier to remove compared to unsoldering T505/2. This eliminates the T505 FBT. If the symptom changes from sequences of two flashes to sequences of four flashes, replace T505. In very rare cases the protection transistor, Q505 in this case, has become leaky. This can generally be determined by checking the transistor with an ohmmeter or diode checker. It is also possible that IC501 has become faulty.
Latch and Hold Down
The latch is activated whenever a condition in the +135 volt OCP or the H Protect circuits causes Q506/B to go HIGH. A HIGH on Q506/B turns it ON, causing it to turn ON Q507. This drops the drive voltage to Relay Drive Q607/B, turning it OFF. This in turn removes the ground return path for RY602 and the unit shuts OFF. During shutdown, the voltage from the Standby 7.5-volt line maintains the latch. You can determine which of the two circuits is activating the latch by checking the voltage at D520/A with a peak hold meter. If that voltage shows a peak near 5 volts, there is a problem with the OCP. The LOW signal created by the latch is also applied to the HLDWN line through R508. The HLDWN line is connected to IC1001 at pin 35. Whenever this line goes LOW, the Self-Diagnostics are activated and the Standby/Timer LED flashes in sequences of two.
H Protect
When the horizontal circuit is operating normally, a signal is output from T505/7 that is also used to supply voltage for the 15 volt line. This signal is sent through R548 and D519 and is used to maintain the charge of C546. The DC voltage created by the charge of C546 is input to IC501/5 Non inverting input through R563. This voltage is compared to a reference voltage of 10.4 volts that is derived by a voltage divider consisting of R561, D517 and D518. D517 is used for temperature compensation. As long as IC501/6 is greater than IC501/5, the horizontal circuit is operating normally. The voltage at IC501/6 is proportional to the High Voltage. If the High Voltage becomes excessive, the voltage at IC501/5 will become
+135
STANDBY 7.5V R508 R661 R630
HLDWN TO IC1001/35 MB BOARD TO POWER RELAY RY602 Q607
D517
D518 RD8.2ES R561
6
+12V
Q507
R571
+
IC501
7
R565 C549
R567 C547 R566
R572 Q506 D520 R558 STANDBY 7.5V
HV DETECT FROM T505/7 +135
R548 D519
5
C546
R563 R556
R553 D516 R554 C551 L510
2
R557
C534 Q505 R559
R663 RELAY FROM IC1001/8 MB BOARD VIA CN2002/7 R642 Q604 D619 MTZJT-77-10B R655 R656 Q608
R568 R555 PART OF T505 FBT
1
+200V
4
STANDBY 7.5V
H DRIVE FROM T501/6 HDT
Q502
A BOARD
+135 OCP AND H. PROTECT 24
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25
Deflection Block
Horizontal
IC1301 YCJ generates the horizontal drive signal and outputs it from pin 34. This signal is first applied to horizontal drive transistor Q501 and is then applied to the horizontal drive transformer T501 and coupled to Q502, the Horizontal Output. The signal from the Horizontal Output is sent to the horizontal yoke and the FBT T505. The horizontal deflection yoke controls the beam scan horizontally. The Horizontal Output circuit also outputs a sample of the H output that is squared off. This signal is called HP. HP is returned to the Pin circuit, YCJ for H phase compensation, and the D board on applicable models to create certain signals used by Dynamic Focus and Quadra-pole. T505 FBT boosts the horizontal drive signal to create the high voltage, G2, heater and focus voltages required by the picture tube. The FBT creates an ABL signal which is representative of the current drawn by the tube. This signal is used to limit the picture brightness and to compensate for high voltage regulation. In addition, scan derived power supplies are generated by the FBT. They are the +200, +12 and 15 volts.
Vertical
The vertical drive signals are generated by the YCJ after it successfully completes initial communication with the Syscon. These signals are output from IC1301/13 and 14 and are applied to IC502 Vertical Out. The output from IC502 Vertical Out is applied to the vertical yoke to control the scanning of the beam vertically. The vertical output also generates a boost pulse that is returned to the Syscon IC for self-diagnostics. This boost pulse is also sent to the D board to create certain signals.
Dynamic Focus and Quadra-pole
The D board is used in all 27" and above models. This is because dynamic focus and Quadra-pole are necessary for larger FD Trinitron tubes. The dynamic focus control uses the VP and HP signals to develop a signal, which will be used to sharpen the left and right sides of the picture. The Quadra-pole circuit uses the VP and HP signals along with the positive vertical drive signal (VD+) to create a signal that will be applied to a series of coils. The magnetic field of these coils is used to sharpen focus in the four corners of the picture.
Pincushion
A 60 Hz parabola signal is output from the IC1301/11 E/W and applied to the Pin Out circuit. This signal is compared with the HP signal to create a Pulse Amplitude Modulated signal that is applied to the Horizontal circuit. The purpose of this signal is to create a uniform picture width on the screen
ABL 3 IN
FBT T505
HD 34 IC1301 Y/C/J HP 33
H.DRIVE Q501, T501
H. OUT Q502 H. CENT. AND LINEARITY PIN OUT CIRCUIT IC501, Q503, Q504
+200V HEATER HV G2 FOCUS 1 H DY+ 2 3 4
H DY-
EW 11
+12V
-15V
5 6
VD+ 13 VD- 14
IC502 V.OUT
V DYV DY+ NECK ASSEMBLY
CN601
IC1001 SYSCON
5
DF/QP DRIVE
QP OUT
MB BOARD
A BOARD
* 27" & 32" ONLY
*
D BOARD
* VA BOARD
DEFLECTION BLOCK 26
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Horizontal Deflection
Overview
Since the Horizontal Deflection circuitry has changed little in the last few years, we will not discuss its circuit description. This section of the course will be used to offer troubleshooting tips for repairing BA-5 chassis sets.
If IC1301 YCJ is outputting HD, the next step is to see if this signal is present at the base of Q501 H Drive. If the signal looks good at Q501/B then the base of Q502 H Out could be unloaded by unsoldering 1 side of R504. This will determine if Q501 can output a signal with its load, T501, connected. The following waveform should be seen at R504 with Q502/B disconnected.
Troubleshooting
The following is a procedure to try if the set is shutting down with a four flashing sequence indication from the Self-diagnostics and No High Voltage present. The presence of High Voltage for even a short time is an indication that the Horizontal circuit is functioning normally and your problem lies in the vertical section. Keep in mind the scan supplies are part of the Horizontal circuit. The YCJ should always output HD whenever 9 volts is present. You can check this by turning the set ON and checking IC1301/19 HD for the signal shown below before the set shuts down. Another method would be to remove the MB board and connect a +9 volt power supply to the 9-volt line. The HD signal should be output from pin 19.
R504 with Q502/B unsoldered 5V 20US
Reconnect R504 if this signal is present. In order to be certain that T501 is capable of handling a load, you should unsolder L510 and R648 (not shown). These components pass the +135 volts through to T505 FBT. These components were chosen because they are easier to unsolder then more evident components, which are soldered to the board where there are eyelets. Note: Before doing this, ensure that SW501 H Centering Switch is in the center position. Otherwise damage will occur to the set. The signal below should be present at Q502/B.
IC1301/19 2V 20US
The only exception would be if IC1301/18 HP is shorted to ground. This pin serves a dual function in previous chassis. In those sets it is the HP/ H OFF line. In these models, during an H protect condition, pin 18 would be grounded and HD at pin 19 would be halted. The H protect circuit does not operate in this manner in the BA-5 chassis, but should IC1301/18 HP be grounded, it would cause HD to cease. IC1301/18 HP should be checked for a short to ground in the event that the YCJ is not outputting HD.
R504 with Q502/6 unsoldered 5V 20US
+9V
33
IC1301 CXA2131AS Y/C/J
44
HP
18
B+ +9V 135V R547 R502 T501 HDT R504
6
HD
19
MB BOARD R383 R385 C502 R510 Q501
MAIN HP R516 Q502
HV
D509
T505 1/2 FLYBACK
R509
1
TO 2nd. ANODE FOCUS G2
C505 C509 C516 C515 C508 C507
D504 200V
SV FV
C535 C501 FROM PIN OUT Q504
3
4
C503 R501 R503 C504
11
ABL R548 C520 D504 C514 B+ 135V
1 2
A BOARD
H SIZE AND LINEARITY CIRCUIT (THIS CIRCUIT DIFFERS DEPENDING ON CRT SIZE
DY
3 4
CN501
HORIZONTAL DEFLECTION 28
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29
Vertical Deflection
Overview
Since the Vertical Deflection circuitry has changed little in the last few years, we will not discuss its circuit description. This section of the course will be used to offer troubleshooting tips for repairing BA-5 chassis sets. If the vertical section is defective, there will be pulses missing on the I protect line to Syscon. If these pulses are missing, Syscon will shut OFF the power relay and the Standby/Timer LED will flash in sequences of four.
If these signals are missing, check IC1301/13 and 14. If these signals are not present, check the data and clock lines at IC1301/34 and 35. The YCJ will not output vertical drive unless communication is okay between the YCJ and the Syscon. If data or clock is missing, unload these lines from each IC individually. When a lead is lifted and the signal returns, replace that IC. If communication appears normal, replace the YCJ. If the drive signals are present, check the signal at IC502/3. This signal should appear as shown below.
Troubleshooting
The following is a troubleshooting procedure for the vertical section if you are sure that the sequence of four flashing lights is not caused by a direct short on one of the power supply lines or a horizontal circuit malfunction. Remember that the chirping transformer in the power supply may indicate a direct short on a power supply line or a power supply problem, and no horizontal is characterized by lack of High Voltage. The first step in checking the Vertical deflection circuit is to check the supply voltages at IC502/2 and IC502/4. If these voltages are missing, R549 and R550 should be checked. These resistors are .47 ohms and should always be checked with an ohmmeter because they have a tendency to change value when subjected to heat. They should never read much higher than .47 ohms with an ohmmeter. Next check the signals at IC502/1 and 7. They should look like the waveforms shown below.
IC502/5 20V 5MS
IC502/3 20V 5MS
If this signal is missing, replace IC502. If the signal appears distorted or is missing the retrace portion, check or replace C541 and D510. Check the output from IC502/5. It should look like the waveform shown below.
If the signal at IC502/5 is missing, replace IC502. Check to be sure that the signal is getting from IC502/3 to the I protect input on the Syscon. The Syscon is located on the MA or MB board depending on the size of the set.
IC502/1 1V 5MS IC502/7 1V 5MS
In the case of size or centering problems, check the values of input resistors R517, R518, R519 and R540.
+12V SCAN D510 DERIVED R550 D514 SUPPLY FROM T503/9
C541
R541
I PROTECT TO CN003/5 MB BOARD
+9V SCL SDA
35 34 33 44 2 6 3
R384
R517
7
IC502 TDA8172 VERT.OUT R518
+
VD+ 13 R387 VD- 14 R540 IC1301 CXA2131AS Y/C/J VTIM
5
FLYBACK GENERATOR DY
5 6
1
4
R519
-15v
R539
C543
R538
5
CN501 R536 -15V SCAN DERIVED SUPPLY FROM T503/7
MAIN VP MB BOARD
R549
D513
A BOARD
VERTICAL DEFLECTION 30
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Video Path 24" and Under
Overview
The following section will discuss the video path for 24" and under BA-5 chassis models. These models have two sets of video inputs and a tuner input. The rear jack may also have an S Video input. These signals are routed through the video switch to the YCJ, then to the Comb Filter if necessary, back through the YCJ, and then output as RGB.
Digital Comb Filter
The Digital Comb Filter is used when composite video inputs are used. The composite video signal output at IC1301/6 is buffered and filtered by Q1311, Q1312, FL1301 and Q1310. You should note that the chroma signal has a very low amplitude at FL1303. The signal is then input to IC1302/14 A In. There is also a 3.58 MHz clock signal output at IC1301/ 43 FSC and input to IC1302/13. This signal is used by IC1302 Digital Comb Filter for timing. The Digital Comb Filter has separate Y and C outputs at pins 20 and 17, respectively. These signals are both buffered and filtered before being re-input to IC1301 at pins 9 and 7.
Switching
The composite video signals from the rear jack J201, the front jack J202 and the tuner are all input to IC1304 Video Switch. IC1304 has two inputs that are used to control the switching. These inputs are V0 and V1 at IC1304/2 and 4. The input to these pins comes from IC1001 Control Tuning System at pins 10 and 11. The following table shows the voltage level at these pins for different input selections:
Input Tuner Video 1 Video 2 IC1304/2 V0 0 Volts 3.3 Volts 0 Volts IC1304/4 V1 0 Volts 0 Volts 3.3 Volts
Y/C Processing
The YCJ selects which Y and C signal to use for processing. If S video is selected then the inputs at pins 2 and 4 are used. If composite video is selected, the inputs at pin 7 and 9 are chosen. Whichever input is chosen, the Y and C signals will be used to create the RGB outputs of IC1301. These signals will eventually be sent to the tube cathodes. The YCJ also contains an input for IK to control AKB. The YCJ samples this signal and determines if each color's cathode is drawing adequate current. If the YCJ determines that there is a problem with the IK loop, video will be blanked. IC1301 YCJ communicates this to IC1001 Control Tuning System through the I²C bus. This IC will then flash the Standby/ Timer LED in sequences of five to indicate an IK problem.
Whichever input is selected will be output from IC1304/7 and then input to IC1301/41. The separate Y and C signals from the S video jack are input directly to IC1301/2 and 4. If the input chosen is composite video, that signal will be switched through the YCJ and output at pin 6. Pin 6 is the monitor out line and would have the Y signal present at its output if an S video source were chosen. This signal will be used by IC1001 Control Tuning System for V Chip and Closed Captioning, and by IC1302 Digital Comb Filter.
J201
1 3 CN2009 20 19 4 2 17 CN2002 18
CN1004 20 19 17 CN1003 18
3 VIDEO1 IC1304 NJM2534M VIDEO 1 TV SW. 7 MAIN VIDEO VIDEO2 OUT 5 V1 V0 2 4
2 4
C1 Y1
IK 21 R OUT 22 B OUT 23
IK RETURN FROM Q1331/C TO Q1317 R BUFFER TO Q1315 B BUFFER TO Q1316 G BUFFER
DET.OUT TU101 J202 FRONT A/V
41
CVBS2 G OUT 24 IC1301 Y/C/J CXA2131AS COMB Y 9
7 CN2001
7 CN1001 TO A BOARD FOR AUDIO SWITCH
10
11
41 29
X1001 8MHz
SELECT0 YM 49 SELECT1 R 52 OSDBLK G 51 24 IC1001 B 50 M37273MF25 258 CV IN CONTROL 22 28 TUNING SYSTEM
29
YS2/YM 32 R2 IN
31 30
Q1332, FL1303, Q1327, Q1328, Q1329
G2 IN B2 IN FSC
43
COMB 7 MON OUT
6
Q1302
Q1313 C1055 C1053
13
Q1354, FL1302, A1306, 1307, Q1311, Q1312, 1308 FL1301, Q1310
14
17
A BOARD
MB BOARD
AIN COUT CKIN IC1302 YOUT 20 TC90A49P DIGITAL COMB FILTER
6CTV27 1223 4/24/00
VIDEO PATH 24" AND UNDER 32
33
RGB Drive
Overview
This section describes how the RGB signals are displayed by the picture tube. In addition, we will discuss the IK/AKB circuit and how it functions in the BA-5 chassis. Troubleshooting no video problems by using the IK pulses output by the YCJ will also be covered.
Place your scope in delayed mode and highlight the area that appears to be one pulse. Expand it and you will see that there are three distinct pulses, one for each color. Your scope should be set to 5ms per division. Some scopes that have less than 100MHz bandwidth may have trouble triggering on these signals. Once the IK detect circuit in the YCJ detects that the proper current is flowing to each cathode, the video is unblanked and a picture may be seen. The YCJ continues to monitor the IK IN line for the proper signal levels. If there is a failure during operation, the Standby/Timer LED will flash in sequences of five.
IK Pulses and Video Blanking
When the set is turned ON and communication is established between the YCJ and Syscon, IK pulses are output for each color. These pulses are one horizontal line in duration and they occur during every field. They are output so they occur on consecutive lines with red first, followed by green and blue. They are buffered by Q1315, Q1316 and Q1317, and applied to CN1303. CN1303 is connected to CN705 on the CB board. The cable connecting the two boards is hardwired and cannot be unplugged from either end. The RGB signals that are applied to the CB board are input directly into pins 1, 2 and 3 of IC702 CRT Drive. IC702 amplifies and inverts these signals, and applies them to the cathode of the tube for their respective colors. If the tube is biased correctly, three lines will be produced in the overscan area of the picture tube. IC702/5 IK outputs a voltage signal that represents the amount of total current being drawn by the tube cathodes. Since each color is outputting a pulse for one H line, in every field we would see a waveform like that shown below at Q1350 or Q1331 Base. It is very hard to see this waveform at other places so it is recommended that you only check IK return here.
Tube Bias
The CRT requires high voltage and other biasing voltages to properly display a picture. First it requires a heater voltage, which is developed by the FBT (not shown) on the A board. The heater is necessary to heat the cathode so that it can emit electrons. If it is missing, the cathode will not emit electrons and consequently there would be no picture. The waveform below shows the signal at CRT pin 7 H1.
CRT Socket/7 20v 10us
The G1 input on the tube is a control grid. There are three separate pins on the tube for G1. They are pins 6, 9 and 13. These pins are connected together and tied to ground through R715. There is approximately -.01 volts present at these pins when no video is input. G2 is also a control grid and is used to limit the acceleration of electrons as they travel through the neck of the tube. These changes in the acceleration of the beam change the picture brightness. G2 measures about 316 volts on a 20" inch sample. This voltage will increase as screen size increases. G2 is set by inputting a gray scale pattern and adjusting the G2 VR on the FBT (not shown) so that the darkest bar is completely black. This is done with Contrast set to max and Brightness set to the midpoint.
Q1331/B 1v 5ms
R1392 Q1350
CN1303
1 3 4
CN705
1 3 4 5 5 3
IK R IN
Q1331 IKIN R1397
21
R1391 9V D1310 UDZ-TB-17 5 AB
R1393
5
IC702 TDA6109JF 2 B IN CRT DRIVE 1 G IN
6
D701 D703
VCC G B R OUT OUT OUT
9 8 7
R709 D702 200V CN502 6 6 FROM D511 CN706 R710 R708 HEATER G2 R711 R716 TO Q1336 AFC BUFFER
10 11
IC1301 CXA2131AS YCJ
35 34
RGB EXPANDED R1379 SDA SCL +9V R1381 R1380
R713 R712 R718
KB
12
KG
5 G2 3 G4
KR HI 7
R1378 R OUT 22 R1396 B OUT 24 R1394 G OUT 23 R1395 Q1317 R1375 Q1315 R1376 Q1316
H1 8 CV G1 13 G1 G1 1
9 6
R714
R715 FOCUS MB BOARD CB BOARD RV701 HSTAT
RGB DRIVE 34
11CTV27
4/25/00
35
There is an input for the focus grid at pin 3 G4 of the tube. This input is from the electrical focus control VR on the FBT. It should be set for optimum focus using a dot pattern. Pin 1 of the tube CV is used for convergence. A part of the H1 voltage is input to pin 1 through RV701. The convergence plates in the tube align the colors to each other using this voltage. If any of these signals are incorrect or missing, the video may never unblank at turn ON. This would leave us with a starting point to troubleshoot blanking problems. Blanking can be caused by faulty IK or tube bias operation. See if the YCJ is outputting a pulse for each color. If there is communication between the YCJ and Syscon, these pulses should be output. Their amplitude should be between 1 and 4 volts peak to peak. If one of these pulses is missing at the RGB outputs of the YCJ, replace it. These same pulses should also be present at the RGB inputs of IC702 on the CB board. If the inputs to IC702 CRT Drive are good there should be an output as shown below. Note it is inverted and much larger.
Troubleshooting
The first step in troubleshooting is to determine if there is a tube bias problem or an IK blanking problem. Use of the Self-Diagnostic feature does not seem to be of any help here. You will know if you are in video blanking if the Standby/Timer LED flashes continuously or in sequences of five soon after turn ON. There should also be HV and sound present. If no HV is present, the Standby/Timer LED should be flashing in sequences of two or four. If a problem occurs with one of the colors, the set will remain in video blanking mode. This means no video or OSD will be displayed. However, the YCJ will continue to output these IK pulses. One possible method for seeing these lines uses the Service Mode. You can enter Service Mode by pressing "Display", "5", "Vol+", then "Power". After the set is ON, press the "1" button 15 times. This will bring you to the VSIZ adjustment although it will not be indicated on the display. Press the "6" button until the IK lines are visible. If one of the colors is missing, troubleshoot the path for that color. If all the colors are missing, you may have a faulty YCJ or tube bias. Note: This method is only valid for BA-5 chassis.
R1392 Q1350
CN1303
1 3 4
CN705
1 3 4 5 5 3
IK R IN
Q1331 IKIN R1397
21
R1391 9V D1310 UDZ-TB-17 5 AB
R1393
5
IC702 TDA6109JF 2 B IN CRT DRIVE 1 G IN
6
D701 D703
VCC G B R OUT OUT OUT
9 8 7
R709 D702 200V CN502 6 6 FROM D511 CN706 R710 R708 HEATER G2 R711 R716 TO Q1336 AFC BUFFER
10 11
IC1301 CXA2131AS YCJ
35 34
RGB EXPANDED R1379 SDA SCL +9V R1381 R1380
R713 R712 R718
KB
12
KG
5 G2 3 G4
KR HI 7
R1378 R OUT 22 R1396 B OUT 24 R1394 G OUT 23 R1395 Q1317 R1375 Q1315 R1376 Q1316
H1 8 CV G1 13 G1 G1 1
9 6
R714
R715 FOCUS MB BOARD CB BOARD RV701 HSTAT
RGB DRIVE 36
11CTV27
4/25/00
37
Video Path 27" and above
Overview
The video path for the 27" inch and above models is very different from the 24" inch and under models. The larger screen size models use the MA board in place of the MB board. This allows for more inputs, including component video and a 2nd tuner for PIP. There are also connections for the additional boards used for PIP and 3D Comb Filter.
model and contains a 3D Comb Filter. Whichever comb filter is used, they will have the same effect on the signal path. They each take composite video input and output separated Y and C. These Comb Y and Comb C signals are then re-input to the YCJ at pins 22 and 20 respectively.
Y/C Processing
IC301 YCJ then switches the correct Y and C input to the demodulator circuits. If the composite source is chosen then the Comb Y and Comb C at pins 22 and 20 are input to the demodulator. If one of the S video inputs is chosen then Y and C from pins 12 and 11, or pins 15 and 14 are selected. The chosen signals are demodulated to YUV signals. Then there is another switch that switches between these signals and the YUV inputs at pins 50, 51 and 52. The chosen YUV signal is then mixed with the PIP YUV inputs. These inputs also contain a Y SW signal at IC301/45 which blanks the main picture for the proper size and position of the PIP window. This signal is then processed further, matrixed to RGB and output from IC301/37, 38 and 39.
Inputs and Monitor Out
Larger BA-5 chassis sets can have up to six inputs. Video 1 and 2 inputs can be composite and S Video. Video 3 input can be composite only. Video 4 is component only. There are also inputs for two tuners. One main is located on the A board and one sub is located on the MA board. The signals are input by the jacks if it is a Video input and from the tuners if it is broadcast video. All of these signals will be output from different connectors on the A board to connectors on the MA board, with the exception of the sub tuner which is already located on the MA board. All signals are input to the YCJ. The YCJ contains switching circuits for component, composite and S Video. The selected composite video or Y signals are output IC301/17 Mon Out. If the selected signal is a composite video signal, it is sent to Q304 and Q306 and then back to the A board for Monitor Out. It is also sent to the B Board or to IC302 Digital Comb Filter. In the case of an S Video, the Y Q304 and Q306 combine their signal with the C signal from IC301/19 with the Y from IC301/17. The output from the transistors is a composite signal that will be sent to the A board for the Monitor Out jack J204. If the component input is chosen, there will be no signal output from Monitor Out.
PIP
The models that have PIP will use the P board, which plugs directly into the MA board. The P board accepts composite video from IC301/24 PIP Out. If the input chosen for PIP by the user is S Video, the YCJ combines the separate Y and C and outputs them as composite video from pin 24. The PIP board will also accept inputs from the YUV component input. When these signals are input to the P board, they are modulated to form a composite video signal. This is because the PIP IC on the P board only accepts composite video inputs. The PIP processor selects one of the composite video inputs, digitizes, demodulates and compresses it. The reduced YUV signal is output from CN305/12, 12 and 14, along with the Y SW signal output from CN305/15. These YUV signals will be placed into the main video YUV signals using the Y SW input.
Comb Filter
If a composite video signal is selected and output from IC301/17, it must have the Y and C components separated. IC302 Digital Comb Filter or the B board can do this. The B board is only used on the KV27FV16
A BOARD CN2005 CN006
2 1 4 2 1 4
3D COMB FILTER Q304, Q306 CV OR Y TO IC001/28 FOR V CHIP B BOARD (27FV16) CN306 1 Q349, Q359, FL301, Q358
3 5
VIDEO1 FROM J201 VIDEO3 FROM J203 MON OUT TO J204* DET. OUT FROM TU101
Y C CV
C320
12
C OUT 19 YI IN MON 17 11 CI IN OUT 9 CVBSI IN
CV CN2006 CN005 1 1 CV
2 2
C321
5
C325 Q151, Q152 C348
3
C