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PSSG
PHILIPS SERVICE SOLUTIONS GROUP
PHILIPS TECHNICAL
TRAINING
E8
COLOR TV
CHASSIS
P H I L I P S Philips Technical Training (USA)
401 E. Old Andrew Johnson hwy
TECH
TRAINING
PO box 555
Jefferson City, TN 37760
VIDEOT A P E S PH: 865-475-0397
FAX: 865-475-0221
MANUALS
EMAIL: [email protected]
E8 OVERALL BLOCK FIGURE 1 The Mono version has a 1 watt
audio amplifier. The Normal
Stereo version has a 2x1 watt
The E8 series chassis is the amplifier. The DBX Stereo version
Small Screen TV chassis produced has a 2x3 watt amplifier. Latin
by Philips Consumer Electronics American versions of this chassis
Company for the 1999-2000 model may have a 2 or 3 watt Mono
year. The E8 is used with 13, amplifier.
19, and 20 inch CRT's. The E8
Tuning System features a 181 The E8 chassis features a
channel Tuning System with On- Switching Mode Power Supply. A
Screen Display. The Tuning System "HOT" ground reference is used in
uses two IC's mounted on the main the primary side of the power
chassis. It consists of a supply. "COLD" (signal)ground is
Microcomputer IC and Memory IC. used from the secondary of the
The Microcomputer communicates power supply and throughout the
with the Memory IC, the Customer rest of the chassis. AN ISOLATION
Keyboard, the Remote Receiver, the TRANSFORMER IS REQUIRED WHEN DOING
U/V Tuner, the TV Signal SERVICE ON ANY CHASSIS.
Processor, the Stereo Decoder
(optional), and the Power On-Off SIGNAL FLOW
circuitry. The Memory IC retains
the settings for favorite The incoming TV RF signal is
stations, customer control applied to the U/V Tuner via the
settings, feature settings, and Antenna and RF input. The
factory setup data. 45.75MHz IF signal is developed
within the U/V Tuner, then
The chassis features a Very Large amplified by an IF Preamplifier
Scale Integration (VLSI) IC for TV located inside the Tuner. The
Signal Processing. This IC amplified IF signal is sent from
performs Video IF, Sound IF, Pins 10 and 11 of the U/V Tuner
AFT/AGC control, Horizontal Signal to the SAW filter, 1003. The SAW
Processing, Vertical Signal filter produces bandpass shaping
Processing, Horizontal/Vertical for the IF signal before it is
Synchronization, Chroma/Luminance applied to the TV Signal
Processing, and Video Switching Processing Integrated Circuit,
between internal and external 7250, for processing. AFT voltage
inputs. On-Screen Graphics from is developed within 7250. These
the Microcomputer are placed on voltage values are then sent to
the main signal within the TV the microcomputer via the I2C bus
Signal Processor. Automatic for Tuner Oscillator frequency
Volume Level (AVL) from the correction.
Microcomputer is sent to the TV
Signal Processor (Mono Sets) and Sound IF signal processing for the
to the Stereo Module (DBX Stereo E8 chassis is performed by
Sets via the I2C bus). AVL for coupling the 4.5MHz Sound IF
Normal Stereo is switched by Pin signal from 7250 Pin 6 through
9 of the Microcomputer, 7600. transistor 7266 and a 4.5MHz band
PAGE 1
PAGE 2
FIGURE 1 - E8 BLOCK
pass filter 1001 to Pin 1 of 7250. between Pin 13, the External Video
In the Mono version, Baseband source on Pin 17, or the External
Audio from Pin 15 of 7250 is Two Video source on Pin 11. The
buffered by transistor 7951 before selected Video is fed to an
being applied to Bass and Treble internal Y/C separator inside
circuits. The outputs of the Base 7250. Luminance and Chromance is
and Treble circuits are applied to fed to an internal SVHS switch
a 1 watt amplifier 7954 in the US which selects between internal Y/C
version or a 2 or 3 watt amplifier or external Y/C on Pins 11 and 10.
7953 in the Latin version. In sets Internally selected "C" Chromance
equipped with a Stereo module, is fed to an internal Demodulator
Baseband Audio from Pin 15 of 7250 which outputs R-Y and B-Y on Pins
is fed to the Stereo Decoder 30 and 29. Internally selected
module. The DBX Stereo Decoder "L" Luminance is output on Pin 28.
module has internal/external R-Y, B-Y, and "L" are fed to the
switching, AVL switching, Matrix circuit on Pins 31, 32, and
volume control, and alignment 27.
settings via the I2C bus (SDA &
SCL). Internal/external switching, Red, Green, and Blue On-Screen
AVL switching, and volume control display signals from the
for the Normal Stereo module are Microcomputer 7600 Pins 34, 33,
performed through individual and 32 are fed to the Signal
control lines from the Processor 7250 Pins 23, 24, and
Microcomputer. Audio Output 25. Fast Blanking from 7600 Pin 35
Amplifiers for both the DBX and is fed to 7250 Pin 26.
Normal Stereo versions are located Brightness, Picture, Sharpness,
on the Stereo module. AVL Color, and Tint control voltages
switching for the Mono version is are developed within 7250 from the
performed in 7250 via the I2C bus. Tuning System Microcomputer 7600
Volume for the Mono set is via the I2C bus. The Red, Green,
controlled in the Audio Output and Blue signals developed by the
Amplifier 7954 or 7953 by a signal processor, 7250, are output
control line from the on Pins 21, 20, and 19 and applied
Microcomputer 7600 Pin 2. Volume to the CRT board. On the CRT
for the Normal Stereo is board, these signals are amplified
controlled in the Stereo Module by before being applied to the CRT.
a control line from the
Microcomputer 7600 Pin 2. Volume The White Balance controls for the
control for the DBX Stereo is CRT set-up are controlled within
controlled in the Stereo Module by 7250 by the Microcomputer via the
the Microcomputer via the I2C bus. I2C bus. Adjustments are
performed with the set in the
Composite Video from Pin 6 of 7250 Service Test Mode. Always use the
is buffered by 7266 and sent to procedures in the Service Manual
1200, a 4.5MHz trap, to remove any for setting up the CRT circuits
sound. The Video is then applied (White Balance). The White Balance
to Pin 13 of 7250. The is set by adjusting the White Tone
Internal/External switch selects adjustments in the Service Test
PAGE 3
Mode. Current, excessive High Voltage,
or a Low +13 volt supply
Horizontal and Vertical signals (VLOTAUX13V). The BCL_PROTN
are also developed within 7250. circuit of the IFT monitors for
Adjustment for Horizontal and excessive Beam Current. If the
Vertical Geometry are done with BCL_PROTN line goes High,
the Remote Transmitter via the transistor 7611 will turn On,
Service Test Mode. There is no causing Pin 16 of 7600 to go Low,
adjustment for the Horizontal turning the set Off. Transistors
Oscillator. The Horizontal circuit 7403 and 7404 monitor the
is a count down type of system secondary of the IFT for excessive
that gets its base frequency from voltage. If the output of the IFT
the 3.58MHz circuit. should go too high, the HEW_PROTN
line will go High, causing Pin 50
When the set is turned On, the Low of 7250 to go High. This will
on Pin 19 of 7600 is removed shut the Horizontal Oscillator
allowing the On/Standby line to go Off. Transistor 7621 and Zener
High. The High is applied to Diode 6612 monitors the 13 volt
7607, the Astable Multivibrator, (VLOTAUX13V) line. If the 13 volt
which is powered by the +5VD supply should go Low or fail, 7621
supply. The Astable Multivibrator will turn On, causing Pin 16 of
7607 provides Horizontal Drive to 7600 to go Low, turning the set
drivers 7608 and 7400. The drive Off. Transistor 7620 provides a
is then applied to 7402, the power On delay for this circuit.
Horizontal Output transistor,
which drives the Horizontal E8 CHASSIS POWER SUPPLY BLOCK
Deflection Yoke and the IFT. The (Figure 2)
IFT develops high voltage, focus
voltage, and filament voltage for When a 120Vac source is connected
the CRT. Scan derived voltages to the E8 chassis, approximately
produced by the IFT are 160 volts, 160Vdc is developed by the bridge
VLOTAUX13V 13 volts, -13 volts, rectifier circuit. The 160 volts
VLOTAUX5V 5 volts, and VLOT8V 8 dc goes through 5545 to the FET
volts. The scan derived VLOT8V,8 switch. The start voltage for the
volt supply, produces the +8VA switching mode power supply is
supply which is applied to Pin 37 taken from the hot leg of the
of 7250 to power the Horizontal input ac.
and Vertical sections of the IC.
The Horizontal Oscillator section The power supply includes a single
of 7250 does not operate until the integrated circuit, operating as a
Scan circuit is working. free-running switching mode power
Horizontal Drive on Pin 40 is supply. The frequency of operation
applied to 7607 to synchronize the varies with the circuit load.
Astable Multivibrator to the There is no separate power supply
correct frequency. for standby; instead, the power
supply turns On when ac is
The Shutdown circuits of the set applied. The switching regulator
monitor for excessive Beam IC starts switching when the
PAGE 4
FIGURE 2 - E8 POWER SUPPLY BLOCK
initial voltage is applied through POWER SUPPLY (Figure 3)
the start circuit. Inside the
switching regulator, the drive When a 120Vac Source is connected
circuit turns the FET switch On to the E8 Chassis, approximately
and Off to allow current to flow 160Vdc is developed by the Bridge
through the primary of the Rectifier circuit. The 160 volts
transformer 5545. Energy stored dc goes through the primary of
in the primary during the On-time transformer 5545 to the transistor
is delivered to the secondaries switch. The startup voltage for
during the Off-time. Feedback from the IC is taken from the hot leg
the Hot secondary is used to of the input ac through resistors
control the switching regulator. 3510 and 3530.
Positive voltage from the hot
secondary is rectified to provide The Power Supply is a Switching
B+ for the switching regulator. Mode type Power Supply. The
The voltages needed to operate the frequency of operation varies with
television are developed from the the circuit load. There is no
secondaries of 5545. 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 PAGE 6
the initial voltage is applied supplied to the IC at Pin 2
through the Startup circuit. The through resistor 3528. Energy is
Switching Regulator turns the stored in transformer 5545 during
Switch On and Off to allow current the On-time of transistor 7518.
flow through the primary of During the Off time of transistor
transformer 5545. Energy stored in 7518, energy is transferred to the
the primary during the On-time is secondaries. Since resistors 3510
delivered to the secondaries and 3530 cannot supply sufficient
during the Off-time. Feedback from current to operate the IC in
the Hot secondary is used to normal operation, the voltage at
control the Switching Regulator. Pin 1 of IC 7520 drops below 9.4
Positive Voltage from the hot volts, which is below the under-
secondary is used as B+ for the voltage lockout reference,
Switching Regulator. shutting IC 7520 Off. 2540 again
charges to 14.5 volts through
From the secondaries of 5541, 10 resistors 3510 and 3530 turning
to 14 volts is developed for the the IC On for a second time.
audio circuit, 95 volts Voltage from Hot secondary Pin 1
for the Horizontal Output, and 14 of transformer 5545 is rectified
volts for the 3.3 volt regulator by diode 6540 charging capacitor
and the 5 volt regulator. 2540 during each startup cycle.
Once 5545 stores enough energy to
STARTUP (FIGURE 3) keep capacitor 2540 above 9.4
volts, the IC operates normally.
AC voltage is rectified by the Capacitor 2530 is connected to the
bridge diodes, 6502 through 6504 Soft Start circuit. The Soft Start
to produce approximately 160 volts circuit prevents the power supply
dc. The 160 volts dc is applied to from operating until the internal
the primary winding of 5545 and to voltages of the IC are at the
the Drain of the switching regu- correct level. This provides
lator FET 7518. additional protection to the power
FET 7518.
A startup dc voltage ramp is
developed when the Hot side of the STANDBY (Figure 3)
ac line charges capacitor 2540
through Startup resistors 3510 and Voltage from Pin 1 of Transformer
3530. When the voltage at 5545 is monitored by Pin 14 of the
capacitor 2540 and Pin 1 of 7520 IC and is compared to a 2.5 volt
IC reaches 14.5 volts, the under- reference for feedback sensing.
voltage lockout of the IC is Resistors 3538, 3539, and 3540 is
overcome. used to set the Bias level at Pin
14 to set the Output Voltage.
The Oscillator inside the IC turns Variable resistor 3540 is adjusted
on, driving the Flip Flop to set the 95 volt secondary
producing a 10 to 15 volt peak to output. When the set is turned
peak drive pulse at Pin 3, turning Off, the reduced load on the
On transistor 7518. The drive secondary is felt by Pin 14 of IC
voltage for the output at Pin 3 is 7520. This voltage change is too
PAGE 7
small for a voltmeter to measure. Supply will restart. The Foldback
The output of the comparator can input on Pin 5 provides overload
be measured at Pin 13 which will protection. This input becomes
be approximately 1.8 volts in inactive when Pin 5 goes above 1
Standby and 2 to 3 volts in the volt.
Full Power Mode. The Standby
Circuit inside the IC monitors the TROUBLESHOOTING
output of the feedback comparator
switching the Oscillator to 20KHz In the case of a Dead Set, first
in the Standby Mode and 70KHz in check the startup voltage at Pin 1
the Full Power Mode. In the of IC 7520. If this voltage is
Standby Mode, the pulse width at missing, check for an open fuse
Pin 3 of 7520 IC is reduced, which 1500, a shorted IC 7520, an open
reduces the On time of transistor diode 6504, a shorted diode 6540,
7518. or open resistors 3510 and 3530.
If there is no output voltage from
FULL POWER (Figure 3) the supply, the voltage a Pin 1 of
IC 7520 should be changing. This
The IC's internal comparator voltage must go to 14.5 volts to
connected to Pin 14 senses a load overcome the undervoltage lockout
change when the set is turned On. of the IC. If the IC is working,
The Standby circuit switches the a dc voltage change can be seen
output to 70KHz and increases the with an oscilloscope at Pin 3 of
outputs On time. The DEMAG circuit the IC at approximately one to two
at Pin 8 of the IC monitors Pin 1 second intervals. Unless the Under
of 5545 through resistor 3520. voltage lockout is switched, the
This circuit keeps Pin 3 of the IC Reference Section will not turn On
from going High until Pin 1 to power the Oscillator and drive
reaches 0 volts. This is to section in the IC.
ensure that FET 7518 will not turn
on until demagnetization of If the voltage is changing at Pin
transformer 5545 is complete. The 3 of IC 7520, check the FET 7518
purpose of this circuit is to and the surrounding components.
increase the efficiency of the
power supply. Pin 7 of the IC For a High Voltage shutdown
senses the voltage across resistor problem, monitor the base of
3518 caused by the current flow transistor 7650 with an
through transistor 7518. If this oscilloscope in the dc mode or a
voltage exceeds 1 volt, the pulse DVM set at the 2 volt range while
width at Pin 3 of the IC, or the turning the set On. If a change
On time of 7518 will be reduced of approximately 0.6 volts is
turning 7518 Off sooner. The observed, 5545 Flyback transformer
internal Overvoltage circuit of would be the likely cause. Also
IC 7520 monitors the VCC at Pin 1 check for the presence of the 9
of the IC. If this voltage goes volt scan derived source when the
above 17 volts, the Power Supply set it turned on.
will shut down. AC power will have
to be removed before the Power
PAGE 8
Symptoms The feedback voltage at Pin 14
will go to zero volts. A random
For a No Power or Dead Set condi- drive pulse will be generated at
tion, first check for shorts on Pin 3.
the output secondaries. Check B+
voltages at Pin 7 of transformer If the Output drive circuit,
5545. A short on the 95 volts B+ transistor 7518 is lost, caused by
line will cause Pin 1 of IC 7520 an open resistor 3525 for example,
to pulse between 9 and 15 volts. and IC 7520 is working, the
FIGURE 4 - E8 HORIZONTAL DRIVE
voltage at Pin 1 of 7520 will set is turned On, the On/Standby
pulse between 9 and 15 volts. An line goes High, allowing the
output pulse at Pin 3 of IC 7520 oscillator 7607 to turn On.
will be seen at the same rate. During Startup, this circuit
operates at a higher Horizontal
E8 HORIZONTAL DRIVE (Figure 4) frequency. The VLOT8V source from
the Sweep circuit produces the
The Power source for the +8VA supply which powers the
Horizontal oscillator is the +8VA Horizontal oscillator in 7250.
supply on Pin 37. This is a scan Horizontal drive from Pin 40 is
derived supply which is not then fed to 7607 to synchronize
present in the Standby mode. the oscillator in 7607 to the
During startup, the oscillator correct Horizontal frequency.
circuit 7607 provides drive for
the Horizontal Output. During
Standby, Pin 4 is held Low keeping
this circuit turned Off. When the
PAGE 9
FIGURE 5 - E8 HORIZONTAL OUTPUT PAGE 10
E8 HORIZONTAL OUTPUT (Figure 5) High, shutting the set Off.
The BCL_PROTN transistor 7401 will
Horizontal drive is fed to 7400 shut the set Off in case of exces-
and then to the Horizontal output sive Beam Current. Excessive Beam
transistor 7402. The Flyback Current will cause the ABLINFO
transformer, 5445, produces High line to go Negative, which will
voltage, Focus voltage, G2 cause Zener diode 6413 to conduct.
voltage, +13 volts, -13 volts, Diode 6414 will be forward
Filament voltage, VLOTAUX5 volts, biased, turning transistor 7401
and the VLOT8V supply. The HEW On, causing the BCL_PROTN line to
protection circuit monitors the go High.
ABLINFO (DAG) line and the -13
volt line for over voltage. If E8 ON/OFF SHUTDOWN CIRCUIT
the voltage on the base of (Figure 6)
transistor 7403 goes above 6.8
volts, transistor 7403 will turn In the Standby mode, a switch
On, turning 7404 On. This will inside 7600 holds Pin 19 Low.
cause the HEW_PROT line to go When the set is turned On, Pin 19
High, shutting the set Off. is released. The Standby line
then goes High through resistor
The BCL_PROTN transistor 7401 will 3617-B3. The base of transistor
shut the set Off in case of 7621 goes High. The VIOTAUX13V
excessive Beam Current. Excessive supply from the Sweep circuit is
Beam Current will cause the applied to the collector of 7620
ABLINFO line to go Negative, which and to the emitter of 7621 through
will cause Zener diode 6413 to zener diode 6612. The positive
conduct. Diode 6414 will be voltage on the emitter of 7621
forward biased, turning transistor keeps the transistor turned Off
7401 On, causing the BCL_PROTN during normal operation of the
line to go High. set. If the VIOTAUX13V supply
should fail, 7621 turns On,
E8 HORIZONTAL OUTPUT (Figure 5) causing Pin 16 of 7600 go Low.
This will turn the set Off. If
Horizontal drive is fed to 7400 the BCL_PROTN should go High,
and then to the Horizontal output transistor 7611 will turn On
transistor 7402. The Flyback causing Pin 16 to go Low, shutting
transformer, 5445, produces High the set Off.
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
PAGE 11
FIGURE 6 -E8 POWER ON SHUTDOWN
PAGE 12
DOES THE SET YOUR PROBLEM IS
DOES THE SET DOES THE SET IS AUDIO
START TURN ON
YES SHUTDOWN AFTER NO HAVE A PICTURE
YES PRESENT
YES BEYOND THE SCOPE OF
TURN ON THIS FLOW CHART
NO YES A NO B NO
IS THE 95 VOLT CHECK KEYSWITCH C
SOURCE PRESENT DOES PIN 19 OF 7600 GO I2C BUS
AT THE CATHODE OF
YES HIGH (5V) WHEN THE NO RESET
DIODE 6550 POWER BUTTON IS OSCILLATOR
PRESSED
E8 CHECK RESISTOR
TROUBLESHOOTING 3207 3411 AND DIODE
CHECK CONNECTIONS 6412 NO
FLOW BETWEEN 7250 AND
YES 5445 IFT
CHART NO YES 7607
MEASURE THE
RESISTANCE FROM
IS DRIVE PRESENT IS APPROX 8 VOLTS
THE CATHODE OF IS DRIVE PRESENT YES IS DRIVE PRESENT NO ON PIN 40 OF 7250 NO PRESENT ON PIN 37
6550 TO COLD ON PIN 3 OF 7607 ON THE BASE OF
OF 7250
GROUND 7402
7607 TRANSISTOR 7908,
TRANSISTOR 7402
RELATED NO YES 7400 NO IC 7250 YES
COMPONENTS TRANSFORMER 5444
IS IT THE
IS THE IS DRIVE PRESENT
NO RESISTANCE > 4K
7402 NO ON THE COLLECTOR YES CORRECT
FREQUENCY
OF 7402
SET IS TURNING ON YES
CHECK FUSE 1500 YES
BRIDGE DIODES
IS A VOLTAGE > 15 RESISTORS 3530 &
IS 140-160 VOLTS IS A DRIVE SIGNAL IS DRIVE SIGNAL
NO PRESENT ON THE YES PRESENT ON THE NO PRESENT ON PIN 3 NO VOLTS PRESENT ON NO 3510
PIN 1 OF 7520 DIODE 6510
DRAIN OF 7518 DRAIN OF 7518 OF 7520
YES
YES YES
PAGE 13
CHECK FEEDBACK CIRCUIT
PIN 1 OF 5545 TO PIN 14 OF RESISTOR 3525
IC 7520
TRANSISTOR 7518
7520
CHECK FOR MISSING HORIZONTAL
DOES THE BASE OF IS THE VLOTAUX13V
IS PIN 50 OF 7250 > 3.9 AND VERTICAL ON PINS 37 AND 36 OF
A 7611 GOT0 0.7 VOLTS
AFTER THE SET IS
NO SUPPLY PRESENT
WHEN THE SET IS
YES VOLTS AFTER TURN ON NO 7600
PROBLEM ON I2C BUS
TURNED ON TURNED ON
YES YES
NO
POSSIBLE EXCESSIVE HIGH
DOES THE VOLTAGE
DODES 6413, 6610 SCREEN GO CHECK THE VERTICAL TUNING CAPS
TRANSISTOR 7401 NO BRIGHT AFTER DRIVE CIRCUIT IFT
IFT THE SET IS TRANSISTORS 7403 AND 7404
TURNED ON
YES
IC 7250
RESISTOR 3416
CRT BOARD
YES
INSERT A SIGNAL INTO
IS OSD (ON
THE REAR JACK IS THE PICTURE IS VIDEO PRESENT CHECK CONNECTIONS
B SCREEN DISPLAY)
PRESENT
YES PANEL AND SELECT PRESENT NO ON PIN 17 OF 7250 NO ON THE PC BOARD
THAT INPUT
IC 7250
NO YES
TUNER
NO IS DRIVE SIGNAL SAW FILTER 1003 NO
IC 7250 IS VIDEO PRESENT ON PIN
PRESENT ON PINS
6 OF 7250 WHEN THE
19, 20 AND 21 OF
TUNER IS SELECTED
7250
YES
YES
TRANSISTOR 7266
IC 7250 BPF 1200
CRT PANEL
PAGE 14
IS VIDEO PRESENT
YES ON PIN 13 OF 7250 NO
IS AUDIO IS THE 14 VOLT SUPPLY
C PRESENT ON PIN
15 OF 7250
YES IS THE SET MONO
OR STEREO
MONO PRESENT ON PIN 1 OF
7954
NO FUSE 1571
NO YES
STEREO
BPF 1001
IC 7250 DOES THE DC
7600 MICRO
VOLTAGE ON PIN 4
VARY BETWEEN 0 AND
NO CIRCUIT
CONNECTIONS
4 VOLTS
IS THE 14 VOLT
AUDIO SUPPLY
PRESENT
NO
YES
FUSE 1571
YES
IS AUDIO
PRESENT ON PINS NO IC 7954
5 & 8 OF 7954
DOES THE DC
VOLTAGE ON THE
VOLUME LINE VARY
BETWEEN 0 AND 4
VOLTS
YES YES
STEREO DECODER
PANEL
NO SPEAKERS
IC 7600
CIRCUIT
CONNECTIONS
PAGE 15