7580937 Philips Chassis E8 Tv Training Manual

PSSG PHILIPS SERVICE SOLUTIONS GROUP

PHILIPS TECHNICAL

TRAINING

E8 COLOR TV CHASSIS

TECH VIDEOT A P E S MANUALS

TRAINING

P H I L I P S

Philips Technical Training (USA) 401 E. Old Andrew Johnson hwy PO box 555 Jefferson City, TN 37760 PH: 865-475-0397 FAX: 865-475-0221 EMAIL: [email protected]

E8 OVERALL BLOCK FIGURE 1

The E8 series chassis is the Small Screen TV chassis produced by Philips Consumer Electronics Company for the 1999-2000 model year. The E8 is used with 13, 19, and 20 inch CRT's. The E8 Tuning System features a 181 channel Tuning System with OnScreen Display. The Tuning System uses two IC's mounted on the main chassis. It consists of a Microcomputer IC and Memory IC. The Microcomputer communicates with the Memory IC, the Customer Keyboard, the Remote Receiver, the U/V Tuner, the TV Signal Processor, the Stereo Decoder (optional), and the Power On-Off circuitry. The Memory IC retains the settings for favorite stations, customer control settings, feature settings, and factory setup data. The chassis features a Very Large Scale Integration (VLSI) IC for TV Signal Processing. This IC performs Video IF, Sound IF, AFT/AGC control, Horizontal Signal Processing, Vertical Signal Processing, Horizontal/Vertical Synchronization, Chroma/Luminance Processing, and Video Switching between internal and external inputs. On-Screen Graphics from the Microcomputer are placed on the main signal within the TV Signal Processor. Automatic Volume Level (AVL) from the Microcomputer is sent to the TV Signal Processor (Mono Sets) and to the Stereo Module (DBX Stereo Sets via the I2C bus). AVL for Normal Stereo is switched by Pin 9 of the Microcomputer, 7600.

The Mono version has a 1 watt audio amplifier. The Normal Stereo version has a 2x1 watt amplifier. The DBX Stereo version has a 2x3 watt amplifier. Latin American versions of this chassis may have a 2 or 3 watt Mono amplifier. The E8 chassis features a Switching Mode Power Supply. A "HOT" ground reference is used in the primary side of the power supply. "COLD" (signal)ground is used from the secondary of the power supply and throughout the rest of the chassis. AN ISOLATION TRANSFORMER IS REQUIRED WHEN DOING SERVICE ON ANY CHASSIS. SIGNAL FLOW The incoming TV RF signal is applied to the U/V Tuner via the Antenna and RF input. The 45.75MHz IF signal is developed within the U/V Tuner, then amplified by an IF Preamplifier located inside the Tuner. The amplified IF signal is sent from Pins 10 and 11 of the U/V Tuner to the SAW filter, 1003. The SAW filter produces bandpass shaping for the IF signal before it is applied to the TV Signal Processing Integrated Circuit, 7250, for processing. AFT voltage is developed within 7250. These voltage values are then sent to the microcomputer via the I2C bus for Tuner Oscillator frequency correction. Sound IF signal processing for the E8 chassis is performed by coupling the 4.5MHz Sound IF signal from 7250 Pin 6 through transistor 7266 and a 4.5MHz band PAGE 1

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FIGURE 1 - E8 BLOCK

pass filter 1001 to Pin 1 of 7250. In the Mono version, Baseband Audio from Pin 15 of 7250 is buffered by transistor 7951 before being applied to Bass and Treble circuits. The outputs of the Base and Treble circuits are applied to a 1 watt amplifier 7954 in the US version or a 2 or 3 watt amplifier 7953 in the Latin version. In sets equipped with a Stereo module, Baseband Audio from Pin 15 of 7250 is fed to the Stereo Decoder module. The DBX Stereo Decoder module has internal/external switching, AVL switching, volume control, and alignment settings via the I2C bus (SDA & SCL). Internal/external switching, AVL switching, and volume control for the Normal Stereo module are performed through individual control lines from the Microcomputer. Audio Output Amplifiers for both the DBX and Normal Stereo versions are located on the Stereo module. AVL switching for the Mono version is performed in 7250 via the I2C bus. Volume for the Mono set is controlled in the Audio Output Amplifier 7954 or 7953 by a control line from the Microcomputer 7600 Pin 2. Volume for the Normal Stereo is controlled in the Stereo Module by a control line from the Microcomputer 7600 Pin 2. Volume control for the DBX Stereo is controlled in the Stereo Module by the Microcomputer via the I2C bus. Composite Video from Pin 6 of 7250 is buffered by 7266 and sent to 1200, a 4.5MHz trap, to remove any sound. The Video is then applied to Pin 13 of 7250. The Internal/External switch selects

between Pin 13, the External Video source on Pin 17, or the External Two Video source on Pin 11. The selected Video is fed to an internal Y/C separator inside 7250. Luminance and Chromance is fed to an internal SVHS switch which selects between internal Y/C or external Y/C on Pins 11 and 10. Internally selected "C" Chromance is fed to an internal Demodulator which outputs R-Y and B-Y on Pins 30 and 29. Internally selected "L" Luminance is output on Pin 28. R-Y, B-Y, and "L" are fed to the Matrix circuit on Pins 31, 32, and 27. Red, Green, and Blue On-Screen display signals from the Microcomputer 7600 Pins 34, 33, and 32 are fed to the Signal Processor 7250 Pins 23, 24, and 25. Fast Blanking from 7600 Pin 35 is fed to 7250 Pin 26. Brightness, Picture, Sharpness, Color, and Tint control voltages are developed within 7250 from the Tuning System Microcomputer 7600 via the I2C bus. The Red, Green, and Blue signals developed by the signal processor, 7250, are output on Pins 21, 20, and 19 and applied to the CRT board. On the CRT board, these signals are amplified before being applied to the CRT. The White Balance controls for the CRT set-up are controlled within 7250 by the Microcomputer via the I2C bus. Adjustments are performed with the set in the Service Test Mode. Always use the procedures in the Service Manual for setting up the CRT circuits (White Balance). The White Balance is set by adjusting the White Tone adjustments in the Service Test PAGE 3

Mode. Horizontal and Vertical signals are also developed within 7250. Adjustment for Horizontal and Vertical Geometry are done with the Remote Transmitter via the Service Test Mode. There is no adjustment for the Horizontal Oscillator. The Horizontal circuit is a count down type of system that gets its base frequency from the 3.58MHz circuit. When the set is turned On, the Low on Pin 19 of 7600 is removed allowing the On/Standby line to go High. The High is applied to 7607, the Astable Multivibrator, which is powered by the +5VD supply. The Astable Multivibrator 7607 provides Horizontal Drive to drivers 7608 and 7400. The drive is then applied to 7402, the Horizontal Output transistor, which drives the Horizontal Deflection Yoke and the IFT. The IFT develops high voltage, focus voltage, and filament voltage for the CRT. Scan derived voltages produced by the IFT are 160 volts, VLOTAUX13V 13 volts, -13 volts, VLOTAUX5V 5 volts, and VLOT8V 8 volts. The scan derived VLOT8V,8 volt supply, produces the +8VA supply which is applied to Pin 37 of 7250 to power the Horizontal and Vertical sections of the IC. The Horizontal Oscillator section of 7250 does not operate until the Scan circuit is working. Horizontal Drive on Pin 40 is applied to 7607 to synchronize the Astable Multivibrator to the correct frequency. The Shutdown circuits of the set monitor for excessive Beam

Current, excessive High Voltage, or a Low +13 volt supply (VLOTAUX13V). The BCL_PROTN circuit of the IFT monitors for excessive Beam Current. If the BCL_PROTN line goes High, transistor 7611 will turn On, causing Pin 16 of 7600 to go Low, turning the set Off. Transistors 7403 and 7404 monitor the secondary of the IFT for excessive voltage. If the output of the IFT should go too high, the HEW_PROTN line will go High, causing Pin 50 of 7250 to go High. This will shut the Horizontal Oscillator Off. Transistor 7621 and Zener Diode 6612 monitors the 13 volt (VLOTAUX13V) line. If the 13 volt supply should go Low or fail, 7621 will turn On, causing Pin 16 of 7600 to go Low, turning the set Off. Transistor 7620 provides a power On delay for this circuit. E8 CHASSIS POWER SUPPLY BLOCK (Figure 2) When a 120Vac source is connected to the E8 chassis, approximately 160Vdc is developed by the bridge rectifier circuit. The 160 volts dc goes through 5545 to the FET switch. The start voltage for the switching mode power supply is taken from the hot leg of the input ac. The power supply includes a single integrated circuit, operating as a free-running switching mode power supply. The frequency of operation varies with the circuit load. There is no separate power supply for standby; instead, the power supply turns On when ac is applied. The switching regulator IC starts switching when the PAGE 4

FIGURE 2 - E8 POWER SUPPLY BLOCK initial voltage is applied through the start circuit. Inside the switching regulator, the drive circuit turns the FET switch On and Off to allow current to flow through the primary of the transformer 5545. Energy stored in the primary during the On-time is delivered to the secondaries during the Off-time. Feedback from the Hot secondary is used to control the switching regulator. Positive voltage from the hot secondary is rectified to provide B+ for the switching regulator. The voltages needed to operate the television are developed from the secondaries of 5545.

POWER SUPPLY

(Figure 3)

When a 120Vac Source is connected to the E8 Chassis, approximately 160Vdc is developed by the Bridge Rectifier circuit. The 160 volts dc goes through the primary of transformer 5545 to the transistor switch. The startup voltage for the IC is taken from the hot leg of the input ac through resistors 3510 and 3530. The Power Supply is a Switching Mode type Power Supply. The frequency of operation varies with the circuit load. There is no separate power supply for standby; instead, the Power Supply turns On when AC is applied. The Switching Regulator IC starts switching when PAGE 5

FIGURE 3 - E8 POWER SUPPLY

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the initial voltage is applied through the Startup circuit. The Switching Regulator turns the Switch On and Off to allow current flow through the primary of transformer 5545. Energy stored in the primary during the On-time is delivered to the secondaries during the Off-time. Feedback from the Hot secondary is used to control the Switching Regulator. Positive Voltage from the hot secondary is used as B+ for the Switching Regulator. From the secondaries of 5541, 10 to 14 volts is developed for the audio circuit, 95 volts for the Horizontal Output, and 14 volts for the 3.3 volt regulator and the 5 volt regulator. STARTUP

(FIGURE 3)

AC voltage is rectified by the bridge diodes, 6502 through 6504 to produce approximately 160 volts dc. The 160 volts dc is applied to the primary winding of 5545 and to the Drain of the switching regulator FET 7518. A startup dc voltage ramp is developed when the Hot side of the ac line charges capacitor 2540 through Startup resistors 3510 and 3530. When the voltage at capacitor 2540 and Pin 1 of 7520 IC reaches 14.5 volts, the undervoltage lockout of the IC is overcome. The Oscillator inside the IC turns on, driving the Flip Flop producing a 10 to 15 volt peak to peak drive pulse at Pin 3, turning On transistor 7518. The drive voltage for the output at Pin 3 is

supplied to the IC at Pin 2 through resistor 3528. Energy is stored in transformer 5545 during the On-time of transistor 7518. During the Off time of transistor 7518, energy is transferred to the secondaries. Since resistors 3510 and 3530 cannot supply sufficient current to operate the IC in normal operation, the voltage at Pin 1 of IC 7520 drops below 9.4 volts, which is below the undervoltage lockout reference, shutting IC 7520 Off. 2540 again charges to 14.5 volts through resistors 3510 and 3530 turning the IC On for a second time. Voltage from Hot secondary Pin 1 of transformer 5545 is rectified by diode 6540 charging capacitor 2540 during each startup cycle. Once 5545 stores enough energy to keep capacitor 2540 above 9.4 volts, the IC operates normally. Capacitor 2530 is connected to the Soft Start circuit. The Soft Start circuit prevents the power supply from operating until the internal voltages of the IC are at the correct level. This provides additional protection to the power FET 7518. STANDBY

(Figure 3)

Voltage from Pin 1 of Transformer 5545 is monitored by Pin 14 of the IC and is compared to a 2.5 volt reference for feedback sensing. Resistors 3538, 3539, and 3540 is used to set the Bias level at Pin 14 to set the Output Voltage. Variable resistor 3540 is adjusted to set the 95 volt secondary output. When the set is turned Off, the reduced load on the secondary is felt by Pin 14 of IC 7520. This voltage change is too PAGE 7

small for a voltmeter to measure. The output of the comparator can be measured at Pin 13 which will be approximately 1.8 volts in Standby and 2 to 3 volts in the Full Power Mode. The Standby Circuit inside the IC monitors the output of the feedback comparator switching the Oscillator to 20KHz in the Standby Mode and 70KHz in the Full Power Mode. In the Standby Mode, the pulse width at Pin 3 of 7520 IC is reduced, which reduces the On time of transistor 7518. FULL POWER (Figure 3) The IC's internal comparator connected to Pin 14 senses a load change when the set is turned On. The Standby circuit switches the output to 70KHz and increases the outputs On time. The DEMAG circuit at Pin 8 of the IC monitors Pin 1 of 5545 through resistor 3520. This circuit keeps Pin 3 of the IC from going High until Pin 1 reaches 0 volts. This is to ensure that FET 7518 will not turn on until demagnetization of transformer 5545 is complete. The purpose of this circuit is to increase the efficiency of the power supply. Pin 7 of the IC senses the voltage across resistor 3518 caused by the current flow through transistor 7518. If this voltage exceeds 1 volt, the pulse width at Pin 3 of the IC, or the On time of 7518 will be reduced turning 7518 Off sooner. The internal Overvoltage circuit of IC 7520 monitors the VCC at Pin 1 of the IC. If this voltage goes above 17 volts, the Power Supply will shut down. AC power will have to be removed before the Power

Supply will restart. The Foldback input on Pin 5 provides overload protection. This input becomes inactive when Pin 5 goes above 1 volt. TROUBLESHOOTING In the case of a Dead Set, first check the startup voltage at Pin 1 of IC 7520. If this voltage is missing, check for an open fuse 1500, a shorted IC 7520, an open diode 6504, a shorted diode 6540, or open resistors 3510 and 3530. If there is no output voltage from the supply, the voltage a Pin 1 of IC 7520 should be changing. This voltage must go to 14.5 volts to overcome the undervoltage lockout of the IC. If the IC is working, a dc voltage change can be seen with an oscilloscope at Pin 3 of the IC at approximately one to two second intervals. Unless the Under voltage lockout is switched, the Reference Section will not turn On to power the Oscillator and drive section in the IC. If the voltage is changing at Pin 3 of IC 7520, check the FET 7518 and the surrounding components. For a High Voltage shutdown problem, monitor the base of transistor 7650 with an oscilloscope in the dc mode or a DVM set at the 2 volt range while turning the set On. If a change of approximately 0.6 volts is observed, 5545 Flyback transformer would be the likely cause. Also check for the presence of the 9 volt scan derived source when the set it turned on.

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Symptoms For a No Power or Dead Set condition, first check for shorts on the output secondaries. Check B+ voltages at Pin 7 of transformer 5545. A short on the 95 volts B+ line will cause Pin 1 of IC 7520 to pulse between 9 and 15 volts.

The feedback voltage at Pin 14 will go to zero volts. A random drive pulse will be generated at Pin 3. If the Output drive circuit, transistor 7518 is lost, caused by an open resistor 3525 for example, and IC 7520 is working, the

FIGURE 4 - E8 HORIZONTAL DRIVE voltage at Pin 1 of pulse between 9 and output pulse at Pin will be seen at the E8 HORIZONTAL DRIVE

7520 will 15 volts. An 3 of IC 7520 same rate. (Figure 4)

The Power source for the Horizontal oscillator is the +8VA supply on Pin 37. This is a scan derived supply which is not present in the Standby mode. During startup, the oscillator circuit 7607 provides drive for the Horizontal Output. During Standby, Pin 4 is held Low keeping this circuit turned Off. When the

set is turned On, the On/Standby line goes High, allowing the oscillator 7607 to turn On. During Startup, this circuit operates at a higher Horizontal frequency. The VLOT8V source from the Sweep circuit produces the +8VA supply which powers the Horizontal oscillator in 7250. Horizontal drive from Pin 40 is then fed to 7607 to synchronize the oscillator in 7607 to the correct Horizontal frequency.

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FIGURE 5 - E8 HORIZONTAL OUTPUT

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E8 HORIZONTAL OUTPUT

(Figure 5)

Horizontal drive is fed to 7400 and then to the Horizontal output transistor 7402. The Flyback transformer, 5445, produces High voltage, Focus voltage, G2 voltage, +13 volts, -13 volts, Filament voltage, VLOTAUX5 volts, and the VLOT8V supply. The HEW protection circuit monitors the ABLINFO (DAG) line and the -13 volt line for over voltage. If the voltage on the base of transistor 7403 goes above 6.8 volts, transistor 7403 will turn On, turning 7404 On. This will cause the HEW_PROT line to go High, shutting the set Off. The BCL_PROTN transistor 7401 will shut the set Off in case of excessive Beam Current. Excessive Beam Current will cause the ABLINFO line to go Negative, which will cause Zener diode 6413 to conduct. Diode 6414 will be forward biased, turning transistor 7401 On, causing the BCL_PROTN line to go High. E8 HORIZONTAL OUTPUT

(Figure 5)

Horizontal drive is fed to 7400 and then to the Horizontal output transistor 7402. The Flyback transformer, 5445, produces High voltage, Focus voltage, G2 voltage, +13 volts, -13 volts, Filament voltage, VLOTAUX5 volts, and the VLOT8V supply. The HEW protection circuit monitors the ABLINFO (DAG) line and the -13 volt line for over voltage. If the voltage on the base of transistor 7403 goes above 6.8 volts, transistor 7403 will turn On, turning 7404 On. This will cause the HEW_PROT line to go

High, shutting the set Off. The BCL_PROTN transistor 7401 will shut the set Off in case of excessive Beam Current. Excessive Beam Current will cause the ABLINFO line to go Negative, which will cause Zener diode 6413 to conduct. Diode 6414 will be forward biased, turning transistor 7401 On, causing the BCL_PROTN line to go High. E8 ON/OFF SHUTDOWN CIRCUIT (Figure 6) In the Standby mode, a switch inside 7600 holds Pin 19 Low. When the set is turned On, Pin 19 is released. The Standby line then goes High through resistor 3617-B3. The base of transistor 7621 goes High. The VIOTAUX13V supply from the Sweep circuit is applied to the collector of 7620 and to the emitter of 7621 through zener diode 6612. The positive voltage on the emitter of 7621 keeps the transistor turned Off during normal operation of the set. If the VIOTAUX13V supply should fail, 7621 turns On, causing Pin 16 of 7600 go Low. This will turn the set Off. If the BCL_PROTN should go High, transistor 7611 will turn On causing Pin 16 to go Low, shutting the set Off.

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FIGURE 6 -E8 POWER ON SHUTDOWN

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DOES THE SET TURN ON

START

DOES THE SET SHUTDOWN AFTER TURN ON

YES

IS THE 95 VOLT SOURCE PRESENT AT THE CATHODE OF DIODE 6550

E8 TROUBLESHOOTING FLOW CHART

DOES PIN 19 OF 7600 GO HIGH (5V) WHEN THE POWER BUTTON IS PRESSED

YES

NO

NO

NO

NO

YES

B

NO

YES

NO

7402

NO

YOUR PROBLEM IS BEYOND THE SCOPE OF THIS FLOW CHART

CHECK RESISTOR 3207 3411 AND DIODE 6412 5445 IFT

YES

NO

IS DRIVE PRESENT ON PIN 40 OF 7250

TRANSISTOR 7908, 7400 TRANSFORMER 5444

NO

IS DRIVE PRESENT ON THE COLLECTOR OF 7402

NO

NO

IS APPROX 8 VOLTS PRESENT ON PIN 37 OF 7250

IC 7250

IS IT THE CORRECT FREQUENCY

YES

SET IS TURNING ON CHECK FUSE 1500 BRIDGE DIODES

YES

C

IS DRIVE PRESENT ON THE BASE OF 7402

NO

IS THE RESISTANCE > 4K

IS AUDIO PRESENT

CHECK CONNECTIONS BETWEEN 7250 AND 7607

IS DRIVE PRESENT ON PIN 3 OF 7607

7607 RELATED COMPONENTS

YES

CHECK KEYSWITCH I2C BUS RESET OSCILLATOR

YES

MEASURE THE RESISTANCE FROM THE CATHODE OF 6550 TO COLD GROUND

TRANSISTOR 7402

A

YES

NO

DOES THE SET HAVE A PICTURE

NO

YES

YES

IS 140-160 VOLTS PRESENT ON THE DRAIN OF 7518

YES

IS A DRIVE SIGNAL PRESENT ON THE DRAIN OF 7518

YES

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CHECK FEEDBACK CIRCUIT PIN 1 OF 5545 TO PIN 14 OF 7520

NO

IS DRIVE SIGNAL PRESENT ON PIN 3 OF 7520

NO

IS A VOLTAGE > 15 VOLTS PRESENT ON PIN 1 OF 7520

YES

YES

RESISTOR 3525 TRANSISTOR 7518

IC 7520

NO

RESISTORS 3530 & 3510 DIODE 6510

YES

DOES THE BASE OF 7611 GOT0 0.7 VOLTS AFTER THE SET IS TURNED ON

A

NO

IS THE VLOTAUX13V SUPPLY PRESENT WHEN THE SET IS TURNED ON

YES

IS PIN 50 OF 7250 > 3.9 VOLTS AFTER TURN ON

YES

NO

CHECK FOR MISSING HORIZONTAL AND VERTICAL ON PINS 37 AND 36 OF 7600 PROBLEM ON I2C BUS

YES NO

DODES 6413, 6610 TRANSISTOR 7401 IFT

DOES THE SCREEN GO BRIGHT AFTER THE SET IS TURNED ON

NO

CHECK THE VERTICAL DRIVE CIRCUIT

POSSIBLE EXCESSIVE HIGH VOLTAGE TUNING CAPS IFT TRANSISTORS 7403 AND 7404

YES IC 7250 RESISTOR 3416 CRT BOARD

YES

IS OSD (ON SCREEN DISPLAY) PRESENT

B

IC 7250

NO

YES

INSERT A SIGNAL INTO THE REAR JACK PANEL AND SELECT THAT INPUT

IS THE PICTURE PRESENT

NO

IS DRIVE SIGNAL PRESENT ON PINS 19, 20 AND 21 OF 7250

IS VIDEO PRESENT ON PIN 17 OF 7250

NO

YES

TUNER SAW FILTER 1003 IC 7250

NO

IS VIDEO PRESENT ON PIN 6 OF 7250 WHEN THE TUNER IS SELECTED

YES YES TRANSISTOR 7266 BPF 1200

IC 7250 CRT PANEL

PAGE 14

YES

IS VIDEO PRESENT ON PIN 13 OF 7250

NO

NO

CHECK CONNECTIONS ON THE PC BOARD

C

IS AUDIO PRESENT ON PIN

YES

IS THE SET MONO OR STEREO

15 OF 7250

NO

MONO

IS THE 14 VOLT SUPPLY PRESENT ON PIN 1 OF 7954

NO

FUSE 1571

NO

7600 MICRO CIRCUIT CONNECTIONS

YES STEREO

BPF 1001 IC 7250

IS THE 14 VOLT AUDIO SUPPLY PRESENT

DOES THE DC VOLTAGE ON PIN 4 VARY BETWEEN 0 AND 4 VOLTS

NO YES FUSE 1571

YES IS AUDIO PRESENT ON PINS 5 & 8 OF 7954 DOES THE DC VOLTAGE ON THE VOLUME LINE VARY BETWEEN 0 AND 4 VOLTS

YES

YES

STEREO DECODER PANEL

NO

IC 7600 CIRCUIT CONNECTIONS

SPEAKERS

NO

IC 7954

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