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PSSG
PHILIPS SERVICE SOLUTIONS GROUP



PHILIPS TECHNICAL
TRAINING


F8
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]
F8 COLOR TV CHASSIS INTRODUCTION. ALWAYS USE AN ISOLATION
TRANSFORMER WHEN SERVICING THIS
CHASSIS FOR YOUR SAFETY.
The F8 chassis is a leader TV
chassis produced by Philips
Consumer Electronics Company for SIGNAL FLOW
the 1999 model year. (Figure 1)
The F8 is used in sets with 25, 27, The incoming RF signal is
and 32 inch screen sizes. The F8 applied to the U/V tuner where
chassis is a global design and is the 45.75 MHz IF signal is
oriented front to rear, or "north developed and amplified. The IF
to south", as it has been called. signal then exits the tuner from
The F8 chassis tuning system pin10 to pass through the SAW
features 181 channels with on- filter. The shaped signal is
screen display. The main tuning then applied to IC 7250, the IF
system uses a tuner, a processor. The automatic gain
microcomputer IC, and a memory IC control (AGC) is performed in IC
mounted on the main chassis. The 7250 and applied to the U/V
microcomputer communicates with the tuner at pin 1. An automatic
memory IC, the customer keyboard, fine tuning signal (AFT) is also
remote receiver, U/V tuner, signal generated in the IC and then
processor IC and the audio output routed to the tuning system via
IC via the I2C bus. The memory IC the I2C bus, to provide
retains the settings for favorite frequency correction as needed.
stations, customer preferred
settings, and service/factory data. Composite Video is output on Pin
6 of 7250 and buffered by
The F8 chassis uses a Very Large transistor 7266. In Mono Audio
Scale (VLSI) Integrated Circuit for sets, the signal is applied to
signal processing. This IC performs 1001, 4.5 MHz Band Pass Filter,
video IF, sound IF processing, AGC and then applied to Pin 1 and
control, horizontal and vertical the Audio Demodulator circuit.
drive and synchronization, also Audio is then output on Pin 15
Luminance/Chrominance processing. and applied to the Audio
The on-screen graphics and closed Amplifier 7953. Volume level is
caption decoding are done within controlled at the Audio Output
the microprocessor, and then sent IC by a control line from the
to the signal processor IC to be Microprocessor. The Audio from
added to the main signal. 7953 is then sent to the
Headphone Speaker output panel.
The F8 chassis utilizes a switch In Stereo sets, the signal is
mode power supply for the main amplified by transistor 7831 and
voltage source. The chassis has a applied to Pin 58 of 7833,
hot chassis ground reference on the Stereo Decoder. The switcher
primary side of the power supply, inside the Stereo decoder IC
and a cold ground reference on the selects between the internal
secondary side of the power supply decoder, FRONTAUDIO1, or
and the rest of the chassis. EXT2AUDIO. The output of the
PAGE 1
FIGURE 1 - BLOCK DIAGRAM PAGE 2
Stereo decoder is fed to the Smart also applied to the
Sound circuit and then to 7950, microprocessor, IC 7600, to pin
Audio Amplifier. The Volume level 37 for On-Screen Display and
is controlled by the Closed-Captioning
Microprocessor, via the Volume synchronization. The Horizontal
line, at the Audio Amplifier IC. drive signal exits IC 7250 from
pin 40 and is applied to 7461,
Composite Video from 7266 is also the Horizontal Driver transistor.
applied to the 4.5 MHz trap, 1200, The signal is amplified and
to remove the audio signal. The coupled to the base circuit of
signal is then applied to Pin 13 of 7460, the Horizontal Output
the IC. The Video switch in 7250 transistor. The H.O.T. drives the
selects between Pin 13, EXT1VIDEO Integrated Flyback Transformer,
on Pin 17, and EXT2VIDEO on Pin 11. which provides high voltage,
The selected signal is then applied screen voltage, focus, G-2, and
to the Y/C Separator. The output filament voltages for the CRT. A
of the YC separator is then fed to scan-derived power supply is also
the SVHS switch which selects provided by the IFT. It supplies
between the output of the YC -11 volts, +11 volts, +50 volts,
separator or external YC on Pins 11 a secondary +5 volt supply, and
and 10. The Y Signal from the YC a +187 volt source for video
separator is output on Pin 28 and drive. The secondary of the IFT
is fed to the Matrix circuits on is monitored by the HEW_PROTN
Pin 27. R-Y and B-Y from the and EHT_INFO lines. These lines
Demodulator is output on Pins 30 are fed to the Signal Processor,
and 29. This signal is then fed to 7250. This circuit will shut
the Matrix circuit on Pins 32 and the Horizontal drive Off in case
31. OSD signal from the of Overvoltage or excessive Beam
Microprocessor is mixed with the Current. Transistor 7482 also
main signal in the Matrix before monitors the Filament line for
being output to the CRT board on Overvoltage. Transistor 7481
Pins 19, 20, and 21. monitors the EHTINFO or DAG line
of Overcurrent. The E_W drive
Vertical and Horizontal drive circuit also monitors for the
signals are also developed inside loss of Horizontal output. If
IC 7250. Vertical drive exits the any one of these three circuits
IC from pin 47, while Horizontal detect a failure, a High will
drive exits at pin 40. These be placed on the STBYON_PROT
signals are a product of a Voltage line. This will turn transistor
Controlled Oscillator Circuit (VCO) 7605 On causing Pin 16 of 7600
and divider network located inside to go Low. The Microcomputer
the chip. Vertical drive is applied will then turn the set Off.
to pin 1 of IC 740, amplified,
shaped, and output from pin 5 where The Power Supply in the set is
it is applied to the vertical On any time power is applied to
winding of the yoke. A feedback the set. The Power Supply
signal is returned to pin 46 of IC produces a 140, 16, and 11 volt
7250. The Vertical sync pulse is supplies. The 11 volt supply is

PAGE 3
applied to 7603 to produce the 3.3 POWER SUPPLY
volt supply for the Microcomputer
and to 6606 to produce the +5VD When a 120Vac Source is
supply. When the set is turned On, connected to the F8 Chassis
the On/Standby line goes High (Figure 2), approximately 160Vdc
turning transistor 7256 On, turning is developed by the Bridge
transistor 7254 Off, which turns Rectifier circuit. The 160 volts
the 8 volt regulator, 7251, On. dc goes through the primary of
This supply is applied to Pin 37 of transformer 5545 to the FET
7250, the Signal Processor IC, to switch. The startup voltage for
power the Horizontal and Vertical the IC is taken from the hot leg
Oscillator. The Horizontal output of the input ac. Operating
drives the Horizontal Output voltage for the driver circuit
section to produce the Scan derived is taken from the HOT side of
sources. 5545, Pin 9.




FIGURE 2 - POWER SUPPLY BLOCK

The Power Supply is a Switching circuit. The Switching Regulator
Mode type Power Supply. The turns the Switch On and Off to
frequency of operation varies with control current flow through the
the circuit load. There is no primary of transformer 5545.
separate power supply for standby; Energy stored in the primary
instead, the Power Supply starts during the On-time is delivered
operating when AC is applied. The to the secondaries during the
Switching Regulator IC starts Off-time. Feedback from the 140
switching when the initial voltage volt supply is used to control
is applied through the Startup
PAGE 4
FIGURE 3 - POWER SUPPLY DIAGRAM PAGE 5
the Switching Regulator via the through resistors 3510 and 3530
Optoisolator feedback. turning the IC On for a second
time. Voltage from Hot
From the secondaries of 5545, 16 secondary Pin 9 of transformer
volts is developed for the audio 5545 is rectified by diode 6540,
circuit, 140 volts charging capacitor 2540 during
for the Horizontal Output, and 11 each startup cycle. Once 5545
volts for the Horizontal stores enough energy to keep
Oscillator, 3.3 volt, and 5 volt capacitor 2540 above 9.4 volts,
regulators. the IC operates normally.
Capacitor 2530 is connected to
STARTUP (FIGURE 3) the Soft Start circuit preventing
the IC from operating until the
AC voltage is rectified by the supplies inside the IC have
bridge 6505 to produce reached the correct operating
approximately 160 volts dc. The voltage.
160 volts dc is applied to primary
winding of 5545 and to the Drain
of the switching regulator FET STANDBY (Figure 3)
7518.
The 140 volt supply is the
A startup dc voltage ramp is reference supply for the power
developed when the Hot side of the supply. The 140 volt supply is
ac line charges capacitor 2540 sampled by resistors 3571 and
through Startup resistors 3510 and fed to the input of the Shunt
3530. When the voltage at capacitor Regulator 7570. Variable
2540 and Pin 1 of 7520 IC reaches resistor 3572 is used to set the
14.5 volts, the under-voltage lock- 140 volt supply to the correct
out of the IC is overcome. level. The Shunt Regulator
drives the feedback optoisolator
The Oscillator inside the IC turns 7581 to set the feedback control
on driving the Flip Flop producing voltage on Pin 14 of 7520.
a 10 volt peak to peak drive pulse Voltage from the Feedback circuit
at Pin 3, turning On transistor is monitored by Pin 14 of the IC
7518. The drive voltage for the and is compared to a 2.5 volt
output at Pin 3 is supplied to the reference for feedback sensing.
IC at Pin 2. Energy is stored in When the set is turned Off, the
transformer 5545 during the On-time reduced load on the secondary is
of transistor 7518. During the Off felt by Pin 14 of IC 7520. This
time of transistor 7518, energy is voltage change on Pin 14 is too
transferred to the secondaries. small for a voltmeter to
Since resistors 3510 and 3530 measure; therefore, the output of
cannot supply sufficient current to the comparator should be
operate the IC in normal operation, measured at Pin 13. The voltage
the voltage at Pin 1 of IC 7520 will be approximately 1.7 volts
drops below 9.4 volts, which is in Standby and 2.7 volts in the
below the under voltage lockout Full Power Mode. The Standby
reference, shutting IC 7520 Off. Circuit inside the IC monitors
2540 again charges to 14.5 volts
PAGE 6
the output of the feedback missing, check for an open fuse
comparator, switching the 1500, a shorted IC 7520, a
Oscillator to 20KHz in the shorted diode in the Bridge, or
Standby Mode and 38KHz in the Full open resistors 3510 and 3530.
Power Mode. In the Standby Mode, If there is no output voltage
the pulse width at Pin 3 of 7520 IC from the supply, the voltage at
is reduced, which reduces the On Pin 1 of IC 7520 should be
time of transistor 7518. changing. This voltage must go
to 14.5 volts to overcome the
FULL POWER undervoltage lockout of the IC.
If the IC is working, a series
The IC's internal comparator, of drive pulses can be seen with
connected to Pin 14, senses a load an oscilloscope at Pin 3 of the
change when the set is turned On. IC at approximately one to two
The Standby circuit switches the second intervals. Unless the
output to 38 KHz and increases the undervoltage lockout is switched,
output's pulse width. The Demag the Reference Section will not
circuit at Pin 8 of the IC monitors turn On to power the Oscillator
Pin 9 of 5545 through resistor and drive section in the IC.
3520. This circuit keeps Pin 3 of
the IC from going High until Pin 1 If the voltage is changing at
reaches 0 volts. This is to ensure Pin 3 of IC 7520, check the FET
that FET 7518 will not turn on 7518 and surrounding components.
until demagnetization of
transformer 5545 is complete. The
purpose of this circuit is to Symptoms
increase the efficiency of the
power supply. Pin 7 of the IC For a no Power or Dead Set
senses the voltage across resistor condition, first check for
3518 caused by current flow through shorts on the output
transistor 7518. If this voltage secondaries. Check B+ voltages
exceeds 1 volt, the pulse width at at Pin 5 of transformer 5545. A
Pin 3 of the IC, or the On time of short on the 140 volt B+ line
7518, will be reduced, turning 7518 will cause Pin 1 of IC 7520 to
Off sooner. The internal pulse between approximately 9
Overvoltage circuit of 7520 IC and 15 volts. The feedback
monitors the VCC at Pin 1 of the voltage at Pin 14 will go to
IC. If this voltage goes above 17 zero volts. A random series of
volts, the Power Supply will shut drive pulses will be generated
down. AC power will have to be at Pin 3.
removed before the Power Supply
will Restart when this occurs. If the Output drive circuit,
transistor 7518 is lost, such as
TROUBLESHOOTING an open resistor 2525 and IC
7520 is working, the voltage at
In the case of a Dead Set, first Pin 1 of 7520 will pulse between
check the startup voltage at Pin 1 9 and 15 volts. A series of
of IC 7520. If this voltage is output pulses will appear at Pin

PAGE 7
3 of IC 7520 each time Pin 1 goes any repair. Resistor 3518 is
to 14.5 volts. the current sensing resistor for
transistor 7518. If 3518 should
If 2530 should become leaky or increase in value, Comparator B
shorted causing Pin 11 of IC 7520 would turn on too soon. This
to go Low, the IC will not Start. would reset the flip-flop too
Capacitor 2530 provides a delay for soon. Transistor 7518 would not
the Soft Start circuit. If Pin 11 remain on long enough to store
is held Low, the output of the Soft sufficient energy in the
Start circuit will remain High. transformer to operate the set.
Resistor 3518 is a precision
If 7518 should fail, resistor 3518, resistor and should only be
which is connected to the source of replaced with the correct part
7518, should be replaced as part of number.




FIGURE 4 - HORIZONTAL DRIVE CIRCUIT


F8 HORIZONTAL DRIVE CIRCUIT Horizontal drive on Pin 40 will
(Figure 4) be shut Off.

When the set is turned On, the F8 HORIZONTAL OUTPUT CIRCUIT
+8VBIMOS voltage is applied to Pin (Figure 5)
37 of 7250. Horizontal drive is
then output on Pin 40 of the IC. Horizontal drive is applied to
HFLYBK is fed to Pin 41 to phase 7461 and to 7460 to drive the
lock the Horizontal oscillator. IFT, 5445. The secondary of
Drive for the E_W circuit is output 5545 produces High voltage, Focus
on Pin 45. If the HEW_PROT or voltage, G2 voltage, +11 volts,
EHTINFO lines should go High, the -11 volts, +50 volts, Filament
PAGE 8
FIGURE 5 - HORIZONTAL OUTPUT CIRCUIT PAGE 9
voltage, and +5 volts. The EHTINFO will place a High on the
line is the DAG line. This line is HEW_PROT line. This will shut
fed back to the Signal Processor the Horizontal drive Off. The
IC, 7250, to adjust the Picture EW_DRIVE from the Signal
level to compensate for changes in Processor drives transistor 7470
Beam Current. The EHTINFO line is to make linearity corrections in
also connected to resistor 3478 and the Horizontal Drive. If
zener diode 6480. If this line Horizontal drive should fail, the
should go excessively negative, source leg of 7470 will go High,
which would be caused by excessive placing a High on the
Beam Current, transistor 7481 will P9STBYON_PROT line shutting the
turn On. This will place a High on set down.
the P9STBYON_PROT line shutting the
set Off. The Filament voltage is MICROPROCESSOR SWITCHING (Figure
monitored for no voltage or 6)
excessive voltage. The Filament
voltage is rectified by 6463 and In the Standby mode, Pin 19 of
fed to the base of transistor 7462. the Microprocessor, 7600, is held
If the voltage on the base of 7462 Low by a switching circuit
goes above 6.8 volts, 7462 will inside the IC. When Set is
turn On, turning 7463 On. This turned On, this circuit switches




FIGURE 6 - MICROPROCESSOR




PAGE 10
Off. Transistor 7256 then turns On If the P9STBYON_PROT line should
through 3608-B. Transistor 7254 go High, transistor 7605 will
then turns Off. The 8 volt turn On. This will pull Pin 16
regulator 7251 then turns On of 7600 Low, shutting the set
placing 8 volts on the +8VBIMOS Off.
line. This source provides power
to the Horizontal oscillator
section of the Signal Processor IC.




PAGE 11
YOUR PROBLEM IS
DOES THE SET DOES THE SET SHUT DOES THE SET IS AUDIO
START TURN ON
YES DOWN AFTER BEING
NO HAVE A PICTURE
YES PRESENT
YES BEYOND THE SCOPE
OF THIS FLOW CHART
TURNED ON



NO C
NO
F8 TROUBLESHOOTING A NO IC 7250 NO NO B
FLOW CHART



IS 8V DC PRESENT IS HORIZ DRIVE IS HORIZ DRIVE
IS 140V VBAT PRESENT ON YES ON PIN 2 OF 7251
YES PRESENT ON PIN
YES PRESENT ON THE
YES TRANSISTOR 7460
THE CATHODE OF 6550
40 OF 7250 BASE OF 7460




NO CHECK 7461
NO TRANSFORMER 5461
NO


MEASURE THE
RESISTANCE FROM
THE CATHODE OF RESISTOR 3608
6550 TO COLD RESISTOR 3525 DOES PIN 19 OF 7600
GO HIGH WHEN THE
NO IC 7600
GROUND DIODE 6514 3.3 VOLT SOURCE
TRANSISTOR 7518 POWER BUTTON IS
PRESSED



NO
CHECK 7460 HOT TRANSISTORS 7256 &
YES 7254




REGULATION
IS THE IS DRIVE SIGNAL FEEDBACK CIRCUIT
NO RESISTANCE > 4K PRESENT ON THE
YES 7581
DRAIN OF 7518 11 VOLT SOURCE




CHECK FUSE 1500
BRIDGE 6505
YES YES YES CHANGE 7520 YES




CHECK RESISTORS
NO IS > 15 VOLTS
IS 140-160 VOLTS IS DRIVE SIGNAL IS VOLTAGE ON PIN 1 OF 3530, 3510
PRESENT ON THE
NO PRESENT ON PIN 3
NO 7520 CHANGING BETWEEN
NO PRESENT ON PIN 1 NO DIODE 6510
DRAIN OF 7518 OF 7520 9.4 AND 14.5 VOLTS OF 7520 BRIDGE 6505
PAGE 12
IS THE EHTINFO DOES THE SOURCE
DOES PIN 16 OF 7600 GO DOES THE COLLECTOR OF DOES THE COLLECTOR
A LOW AFTER THE SET IS
YES LINE < -28 VOLTS
NO 7482 GO TO 11 VOLTS WHEN
NO OF 7481 GO TO 11 VOLTS
NO OF 7470 GO HIGH
WHEN THE SET IS
TURNED ON THE SET IS TURNED ON WHEN THE SET IS
TURNED ON
TURNED ON



RESISTOR 3485 TRANSISTOR 7482
NO DIODE 6485
YES FILAMENT VOLTAGE
YES
NO


7481
7605
YES
IS > 3.9 VOLTS DIODE 6480
IS 186 VOLT
PRESENT ON PIN 50 OF
NO SUPPLY PRESENT
7250 WHEN THE SET IS TO THE CRT
YES TURNED ON BOARD YES




TRANSISTOR 7462 & 7470
7463
IFT
NO MICRO 7600
CRT BOARD
TUNING CAPS I2C BUS
CHECK HEADPHONE
SWITCH YES
SPEAKERS




INSERT AUDIO INTO
IS AUDIO IS AUDIO
IS THE SET THE REAR JACK IS AUDIO
B STEREO OR MONO
STEREO PANEL AND SELECT PRESENT
NO PRESENT ON PINS
28 & 29 OF 7833
YES PRESENT ON PINS
8,10,11,&13OF
THAT INPUT
7950




CHECK HEADPHONE FUSE 1573
MONO YES NO
JACKS AND YES
SPEAKERS


TRANSISTOR 7831 NO
IC 7833 IS 16V PRESENT
IS AUDIO IS AUDIO IC 7833
IC 7250 ON PIN 4 OF 7950
1001 4.5 BPF
NO PRESENT ON PIN 3 YES PRESENT ON PINS
OF 7953 6 & 8 OF 7953



IC 7600
ANTI-POP CIRCUIT
YES
NO
YES IC 7953




IS THE DC VOLTAGE ON PINS
NO 2 & 8 OV 7950 BETWEEN 0-1
PAGE 13




DOES THE VOLTAGE ON PIN
IS 16 VOLTS DC MICRO 7600 VOLTS AS THE VOLUME IS
FUSE 1573 NO PRESENT ON PIN 2
YES 5 OF 7953 VARY BETWEEN 0- NO ANTI POP CIRCUIT ADJUSTED
1 VOLTS AS TEH VOLUME IS
OF 7953 IC 7950
ADJUSTED




YES
INSERT A COMPOSITE
IS OSD (ON VIDEO SIGNAL INTO
DOES THE SET
C SCREEN DISPLAY)
PRESENT
YES HAVE A JACK
YES EXT1 AND SELECT
THAT INPUT IN THE
IS VIDEO PRESENT
ON SCREEN
PANEL 7250
MENU




NO NO
CRT BOARD



SELECT THE TUNER IN IS LUMINANCE
THE MENU AND PRESENT ON PIN
IS RGB PRESENT ON NO CHECK FOR YES 28 OF 7250
PINS 21, 20, AND 19 OF COMPOSITE VIDEO ON
7250 PIN 6 OF 7250
YES
7250
YES



CHECK RESISTOR
7250 3490,7480IC,IFT IS LUMINANCE
IS VIDEO PRESENT YES IS VIDEO PRESENT ON YES
PRESENT ON PIN
ON PIN 6 PIN 13 OF 7250
27 OF 7250




1003 SAW FILTER
NO NO NO


TRANSISTOR 7266 CHECK CIRCUIT
YES 1200 4.5MHz TRAP BOARD CONNECTIONS
NO
IS 5V SUPPLY PRESENT
ON PIN 7 OF THE
TUNER
CHECK RESISTOR
IS PICTURE
3442, DIODE 6008,
PRESENT ON THE NO 7250
TUNER, RESISTOR
SET
3488,IFT
YES




IS 33V PRESENT
TUNER
ON PIN 9 OF THE
NO
TUNER



YES
YES


DISCONNECT PINS 10
INSERT AN IF SIGNAL & 11 OF THE TUNER
IS THE PICTURE
PAGE 14




ON PINS 48 AND 49 OF NO PRESENT ON THE
AND APPLY AN IF
7250 SIGNAL TO THE
SET
CIRCUIT FOIL