Philips H8 Installation guide

philips technical training
401 e. old andrew johnson hwy
p.o. box 555
jefferson city, tn 37760
phone: [phone]
fax:[phone]
email: [email protected]
PHILIPS
TECH
VIDEOTAPE S
MANUALS
TRAINING
PSSG
PHILIPS SERVICE SOLUTIONS GROUP
H8 CHASSIS
TECHNICAL TRAINING
MANUAL
2001 RTM TRAINING

TABLE OF CONTENTS
AUDIO OUTPUT 24
AUDIO SIGNAL PROCESSOR 24
BOARD LOCATIONS 2
CUSTOMER CONTROL INTERFACE 28
DOUBLE WINDOW 19
DOUBLE WINDOW VIDEO SIGNAL FLOW 19
HEADPHONE AMPLIFIER 24
HORIZONTAL AND VERTICAL DRIVE 7
HORIZONTAL OUTPUT AND SHUTDOWN 7
INTRODUCTION 1
MICROPROCESSOR 29
M-LINK 34
NON PIP VIDEO SIGNAL FLOW 8
POWER DOWN AND FRONT DETECT 6
PIP CIRCUIT 15
PIP VIDEO SIGNAL FLOW 15
SERVICE MODES 33
SIDE JACK PANEL 28
STANDARD CRT DRIVE 12
STANDBY REGULATORS AND ON/OFF 5
SWITCH MODE POWER SUPPLY 3
TROUBLESHOOTING FLOW CHARTS 35
VERTICAL OUTPUT 8
VERY FLAT CRT DRIVE 22

INTRODUCTION
The H8 TV Chassis is designed for the 2000-
2001 model years. It comes in three screen
sizes which are 27, 32, and 36 inch. All
Chassis versions have a Side Jack Panel, a
Component Input, and Surround Speaker
Jacks. The Rear Jack and Side Jack Panels
are equipped with both Composite,
Component, and SVHS inputs. The sets are
equipped with either a Standard Dark Glass
picture tube or a Very Flat Square Invar
picture tube.
The H8 Chassis comes in Non-PIP (Picture in
Picture), Single Tuner PIP, two Tuner PIP, or
Double Window versions. Each time the User
selects the PIP window, the PIP window
appears, changes size, then disappears. In
the Double Window version when the PIP
On/Off button on the Remote is pressed, a
PIP window appears. When the button is
pressed again, the window changes size.
Press it again and the picture goes to a
double window (split screen). Pressing the
button again, the picture returns to normal.
The XXPT41 and larger models are equipped
with the M-Link feature. The M-Link
feature allows VCRs, DVD, etc to be
controlled through the TV. Up to five
devices can be controlled. Refer to the
Model to Module listing in the Service
Manual to determine which modules are
in a given model.
Other features include an Audio Volume
Leveler (AVL) to compensate for
changes in volume level. AutoLock
which allows certain channels, or
programs with certain ratings to be
blocked. Each time the set is turned Off
and back On, the Access Code must be
reentered to view the blocked channels.
If the Customer forgets the Access Code,
entry into the Menu to change the code
can by obtained by entering Access
Code 0711. To gain entry, the code must
be entered twice.
A Format selection in the menu allows
the user to select between 4x3, Zoom, or
16x9 aspect ratio for the picture. This is
accomplished by changing the Height
and Width settings in the set.
Page 1
The following table refers to the models and features:
27PT31 NON PIP
27/32/36PT41 Single Tuner PIP
27/32/36PT71 Two Tuner PIP
27/32PT81 Real Flat Invar CRT - Two Tuner PIP - SCAVEM
27/32PT91 Real Flat Invar CRT - Double Window - Guide Plus
Virtual Dolby - SCAVEM - Histogram

Page 2
H8 CHASSIS BOARD LOCATIONS
TV BLOCKING OPTIONS NON PIP CHASSIS VIEW

POWER SUPPLY
Switch Mode Supply (Figure 1)
The Power Supply is a Switching type supply.
The Power Supply begins operating as soon
as AC power is applied to the set. AC power
is applied to the Large Signal Board through
Fuse 1900 and applied to the Bridge Rectifier
6915. The rectified B+ voltage is applied to
the regulator switching IC, 7921, through Pins
6 and 3 of transformer 5912. Startup voltage
for the supply is applied to Pin 4 through
resistors 3914 and 3913. The Zener Diode
6921 prevents the voltage on Pin 4 from
exceeding 33 volts in case the Regulator IC is
not working. When the voltage on Pin 4
reaches 16 volts, the Oscillator inside the IC
begins operating. Once the Supply is in full
operation, the operating voltage for the supply
is supplied by Pin 8 of 5912 and is rectified by
6929. The Oscillator drives the internal
switching FET. When the FET is On, energy
is stored in 5912. When the FET is Off,
energy is transferred to the secondary of
5912. The Frequency and On time of the
internal switching FET is determined by the
Internal Comparator, the internal RC network,
and the Magnetizing Inductance of the
Transformer. The Internal RC network also
determines the Off time of the FET switch.
The On Time is determined by the ramping
voltage across 3924, 3923, the feedback
voltage from Pin 8 of the transformer, and the
voltage from the feedback opto-isolator. The
Reference Voltage for the supply is the VBAT
(135 volt source). This source is sampled
by 7971 which drives the feedback
opto-isolator 7929 to set the switch time of
comparator B. This controls the On time of
the internal switching FET to maintain the
VBAT voltage at the correct level. There
are four output voltages from the
transformer which are the VBAT voltage, 8
volts to the 5 and 3.3 volt regulators, 8
volts unregulated, and 27 volts for the
Audio Output circuit.
To troubleshoot the Power Supply, first
check the VBAT (135 volt source). If this
voltage is missing, check for a short on the
VBAT line. The most likely cause would be
a shorted Horizontal Output Transistor. If
the voltage is pulsing or is Low, check the
feedback circuit, 7971 and 7929. Also
check Fuse 1941 on the 8 volt unregulated
supply. This line supplies the operating
voltage for the feedback circuit. Next,
check the B+ voltage for 7921 on Pin 3. If
the drive signal is pulsing On and Off on
Pin 3, there may be a problem with the
feedback circuit. If there is no drive signal
on Pin 3, check for the operating voltage
on Pin 4. This voltage must ramp to 16
volts to start the supply. If it is missing or
is not ramping to 16 volts, check 3913,
3914, and 2919. Regulation problems
could be caused by resistors 3923 or 3924
changing value. If 7921 should fail, these
resistors should be changed by using
original parts only.
Page 3

Set Turned On.
Set in Standby.
Page 4 Figure 1 - Switch Mode Power Supply

Standby Regulators and On/Off (Figure 2)
The voltage from jumper 9964 (approximately
8 volts) is used to produce the 3.3 volt
standby, 5 volt standby, 5 volt remote control,
and switched 8 volt supplies. The voltage is
applied to transistor 7965 to produce the 3.3
volt Standby supply. When the set is in the
Standby mode, transistor 7944 is turned On,
turning 7922 On, providing a extra current
drive for the 3.3 volt regulator. The 8 volt
unregulated supply is applied to 7942,
which is a switched 8 volt regulator. The
Standby line goes Low when the set is
turned On, turning transistor 7944 Off,
switching 7942 On. The switched 8 volt
supplies the Horizontal Oscillator in the
Signal Processor IC located on the SSB.
Five Volt Switch (Figure 3)
The Switched 8 volt supply also turns On the
5 volt regulator, 7967, to produce a switched 5
volt supply. The Switched 5 volt supply turns
transistor 7950 On. This provides a load on
the 27 volt Audio Supply line to discharge any
remaining voltage on the line in the event that
power is removed from the set while it is
being turned On. This is necessary to
prevent a POP in the speaker while the set
is powering down.
Figure 2 - Standby Regulators and On/Off
Page 5

Power Down and Front Detect (Figure 4)
The Power-Down and Front Detect circuits
signal the Microprocessor in case power is
removed from the set. The Microprocessor
will store the customer settings before shutting
the set down. Diode 6942 produces a negative
voltage to turn transistor 7987 On, keeping the
Power-Down line High. This keeps transistor
7277 turned Off. If power is removed from the
set, the negative voltage will discharge before
the operating voltage for the set falls.
Transistor 7987 will turn Off. 7277 will then
turn On, placing a High on the RGB CRT drive
lines, blanking the CRT. Transistor 7277
will continue to conduct until Capacitor
2284 has discharged. In the same manner,
7990 will be turned Off, turning 7991 Off,
which will turn 7992 On, causing the Front-
Detect line to go Low. This will prevent the
Microprocessor from receiving any
commands while the set is being shut
down. If there is a problem in this circuit
which causes the Front Detect line to go
Low, the Microprocessor will not respond to
any commands from the Keyboard or
Remote.
Figure 3 - 5 Volt Switch
Page 6
Figure 4 - Power Down and Front Detect

SWEEP AND SHUTDOWN CIRCUITS
Horizontal and Vertical Drive (Figure 5)
The 3.3 volts Standby supply provides power
to 7301 on Pin 14 for a Horizontal Soft Start.
The Standby line from the Microprocessor
turns the +8 volt supply On to provide power
for the Sync circuits when the set is turned
On. The Horizontal Output on Pin 56 is
switched On by the Microprocessor via the
I2C buss, after the Soft Start is complete.
Vertical Drive, labeled Frame-Drive, is output
on Pins 63 and 64. In the event the Vertical
Output should fail, the Signal Processor 7301
will blank the RGB output. East-West Drive
on Pin 62 provides linearity correction for the
Very Flat and Larger CRTs. Sandcastle is
output on Pin 57. The Dynamic Phase
Correction input on Pin 58 has two functions.
One function is to provide Horizontal
Phase correction for the Horizontal Drive.
The other is to provide Flash protection in
case of an overvoltage on the I-Beam line.
If the pulse on Pin 58 exceeds 6 volts,
Horizontal Drive will be shut Off. It will be
necessary to recycle power to the set to
restore operation. This failure will
generate an error code 1 indicating a
problem with the Horizontal Output
Transformer or with the CRT drive circuit.
The PROTN line is connected to the
IBEAM (Dag) line. This voltage is used to
make minor adjustments in the Vertical
Drive to compensate for minor changes in
Beam Current. This line is also connected
to the Overvoltage Detection circuit. If this
voltage exceeds 3.9 volts, the Horizontal
Drive will be shut Off. The Microprocessor
will show an error code 3.
Horizontal Output and Shutdown (Figure 6)
Horizontal Drive (LINEDRIVE1) is fed to
transistor 7481 and coupled through
transformer 5406 to the Horizontal Output
transistor 7410. In sets with the Very Flat
CRT and larger screen sizes, an East West
Drive circuit is present. The East West
Drive circuit also has a protection circuit to
detect the loss of Horizontal drive. In nor-
mal operation, 7470 is switched by the
EW-Drive. The pulse width is too narrow
to develop the necessary voltage to turn
7478 On. Current flow through 3479
keeps transistor 7480 turned On, keeping
Figure 5 - Horizontal and Vertical Drive
Page 7

the PROT-UP line Low. If Horizontal drive or
EW Drive is lost, 7470 is turned On, applying
a positive voltage to the base of 7478, turning
it On. Transistor 7480 turns Off, causing the
PROT-UP line to go High through resistor
3480, which will cause the Microprocessor to
turn the set Off.
When the Driver Transistor 7481 is
conducting, the voltage drop across resistors
3404, 3405, and 3406 turns transistor 7408
On. This circuit supplies the 33 volt tuning
voltage and bias voltage to the IBEAM (Dag)
circuit. Transistor 7440 also detects the
failure of Horizontal Drive or Overcurrent. If
there is no Horizontal drive to 7481, 7408 will
turn Off, removing the 33 volt tuning voltage.
Transistor 7440 will turn On, causing the
PROT-UP to go High, which will cause the set
to shut Off. Voltage from Pin 5 of the IFT is
rectified by 6461 and applied to 7464. If this
voltage exceeds 5.4 volts, 7464 will turn On,
turning 7467 On, applying the +8 volt supply
to the PROTN line, shutting the set Off. The
IFT produces a plus and minus 13 volt supply
for the Vertical Output circuit. The voltage on
Pin 9 of the IFT is rectified by 6445 to produce
a +200 volt supply for the CRT output
circuit. The Horizontal Drive signal is
sampled by 3411, 3412, and 3413 to
produce the HFB (Horizontal Feedback
signal) which is used to provide Sync for
the Small Signal Board.
Vertical Output (Figure 7)
Positive and Negative Vertical drive from
the Small Signal Board is fed to the
Vertical Output IC7501 which drives the
Vertical Yoke. The Vertical Pulse on Pin3
drives 7513 to produce the VFB (Vertical
Feedback signal) for the Small Signal
Board. A failure in the Vertical Output
circuit will be detected by the Signal
Processor on the SSB by sensing the
Frame Drive line and by the
Microprocessor sensing the loss of the
VFB pulse. While turning the set On,
check the plus and minus 13 volt sources.
Then check for Vertical Drive on Pin 7 with
an oscilloscope while turning the set On.
Page 8
VIDEO SIGNAL FLOW
There are four variations in the signal flow
path for the H8 chassis. They are the Non-
PIP, the Single Tuner PIP, the Dual Tuner PIP,
and the Double Window version.
NON PIP Video Signal Flow (Figure 8)
The first version to be discussed is the Non
PIP chassis video path. The Main Tuner, AV1,
AV2, and Component Inputs are located on
the Large Signal panel. The AV3 input is
located on the Side Jack Panel. All of
these inputs are fed to the Small Signal
Board, SSB, which plugs into the Large
Signal panel. The Tuner IF is fed to the
SAW filter, 1451, and then to the Signal
Processor, 7301, on Pins 1 and 2.
Composite Video is output on Pin 16 and is
buffered by 7305 and 7331. Baseband
Audio is output on Pin 27 and is buffered
by 7307. This signal is fed to the Sound
Decoder IC for processing. The Video
Signal is then fed to 7301 on Pin 24 which
selects between the composite signal and

Page 9
Figure 6 - Horizontal Output and Shutdown

Page 10 Figure 7 - Vertical Output

Figure 8 - Non PIP H8 Video Signal Flow Page 11

the MAIN-CVBS-EXT-IN. The MAIN-CVBS-
EXT-IN is selected composite Video or
Luminance from either AV1, AV2, or AV3.
These signals are selected by the Switch IC
7401 which is controlled by two lines from the
Microprocessor, which are SEL-MAIN-R1R2
and SEL-MAIN-FRNT-RR. If SVHS is the
selected input, the Y (Luminance signal) is fed
to Pin 29 by 7401. Selected Video or Y from
7301 is output on Pin 54 and is buffered by
7421. If the output of 7301 is Composite
Video, the Comb Filter IC 7405 will output Y
and C on Pins 15 and 13. Switching IC 7407
selects YC from either the Comb Filter or Y
from 7421. If one of the SVHS inputs is
selected, 7401 outputs C (Chrominance) on
Pin 14 and is buffered by 7412-B before being
fed to 7407. IC 7407 is switched by Pin 22 of
7301. A High on Pin 22 causes Pins 12 and
13 to switch the inputs on Pins 1 and 11.
When Pin 22 is Low, 7425 is turned Off
switching Pins 5 and 6 High, selecting the
inputs on Pins 4 and 8. Selected YC is then
fed to Pins 21 and 20 of 7301 where they are
fed to a Delay Line and Demodulator. The
output of the Demodulator and Delay Line is
fed to a YUV switch, which selects between
this signal and external YUV (Component
Input) from the Jacks on the Large Signal
panel. The selected YUV signal is then fed
back into 7301 on Pins 39, 47, and 48. The
signal is then fed to a YUV processing circuit
and to an RGB Matrix where OSD (On Screen
Display) is added. The signal is then fed
to the RGB output circuit and to the CRT.
A Test Waveform is first sent to the CRT
on the RGB lines. When this Test Signal is
detected by the CRT drive circuits, the
signal is fed back to 7301 on Pin 3 on the
CUTOFF LINE. When these are detected,
the Video signal is then output on the
RGB lines.
Standard CRT Drive (Figure 9)
The CRT drive signal is fed to 7830 which
drives the CRT. As mentioned previously,
a Test Signal is sent to 7830 and to the
CRT. The Waveform on the left shows this
Test Signal. When 7830 senses the
correct current flow in the CRT, the Test
Signal is sent to the SSB via the CUTOFF
line. The Picture RGB signal is then fed to
the CRT Board. This waveform is shown
on the right. If the CRT is defective or
unplugged, no pulse will be ouput on Pin 4.
Therefore, the Signal Processor IC on the
SSB will not output the Video Signal on the
RGB lines.
Figure 9 - Standard CRT Drive Circuit
Page 12

Page 13
Figure 10 - Video Signal Flow with Standard PIP

Figure 11 - Single Window PIPPage 14

PIP (Picture in Picture) Video Flow (Figure
10)
There are two PIP chassis versions which are
the Single Tuner and Two Tuner sets. Video
Signal flow for the Single Tuner PIP version is
the same as the Two Tuner version, except
the Composite Video from Pin 16 of 7301 is
routed through the Large Signal Board (LSB)
to the PIP module and back to the 1333
Sound Trap in the Two Tuner version. In the
Single Tuner version, Video from Pin 16 is
routed through jumper 4308. The second
Tuner is located on the PIP panel. Baseband
audio is output on Pin 27 and is buffered by
7331. In the Two Tuner version, the Audio is
combined with the composite video before
being fed to the PIP panel. Selected Video
with the Baseband Audio from the PIP panel
is fed through jumper 4307 to the Audio
Processor. In the Single Tuner version,
Baseband Audio from 7331 is fed through
jumper 4304 to the Audio Processor. YUV
signal from Pins 40, 45, and 46 are routed
through the PIP module where the PIP
window Video is inserted. Other Video signal
flows are the same as for the Non-PIP
version. The Single and Two Tuner PIP
circuits are the same except for the addition of
the second Tuner and Signal processing
circuits on the PIP panel.
PIP Circuit (Figure 11)
The PIP comes in two versions, Single
Tuner with no tuner on the PIP panel and
two tuner versions with the second tuner
located on the PIP module. Output of the
second tuner is fed to the SAW FILTER
1901, and to the Signal Processor 7914.
Composite Video is fed to the Switch 7916
which selects between the PIP tuner or
selected Composite Video from the SSB.
There are two sets of switches: one to
select Video for the main picture, CVBS-
PIP_TUN1-2-CVBS-IN, and one to select
Video for the PIP window. Selected Video
for the PIP window is fed to 7801, which
selects between the output of 7916 or from
AV1, AV2, or the Side Jack panel (labeled
Front In). The output of 7801 is buffered
by a four transistor amplifier and then fed
to Pin 22 of 7803, PIP processor. The PIP
processor is controlled by the I2C buss
(SDA and SCL). It is kept in sync by the
Vertical sync pulse (VFB) and the
Horizontal sync pulse (SANDCASTLE).
The PIP window video is output as YUV to
the YUV switch, 7919. The signal is
combined with the main picture YUV from
Page 15
Model 27PT81 - Very Flat CRT - Two
Tuner PIP

the SSB panel on connector 0205. The
combined YUV signal is output on Pins 12, 11,
and 10 to the SSB.
PIP Switching (Figure 12)
Control for the PIP panel is performed by
7910 via the I2C buss. SEL_TUNER1 and
SEL_TUNER2 control the composite
switching to the SSB panel. S1, S2, and S3
control the tuner aux switching IC 7801.
PIP Power Supply (Figure 13)
The PIP panel is powered by +5 volt, +8
volt, and +33 volt supplies from the Large
Signal Board (LSB). A 3.3 volt regulator
supplies power to the PIP processor, 7803.
Page 16

Figure 12 - Single Window PIP Control
Figure 13 - PIP Power Supply
Page 17

Page 18 Figure 14 - Video Signal Flow with PIP/Double Window