Philips B8 Series User manual

Color Television Chassis
B8 Series Chasssis
Manual 7562
Service
Service
Service
Contents
5. Service Modes, Error Codes and Faultfinding
6. Block Diagrams and Testpoints
7. Electrical Diagrams and PWB's
B8CHASSIS TABLE OF SCHEMATIC DIAGRAMS
MAIN CHASSIS (SECTION 1OF 5)
MAIN CHASSIS (SECTION 2OF 5)
MAIN CHASSIS (SECTION 3OF 5)
MAIN CHASSIS (SECTION 4OF 5)
MAIN CHASSIS (SECTION 5OF 5)
CRT PANEL (13", 19", & 20")
CRT PANEL (25" & 27")
KEYBOARD/SOUND SHAPER PANEL
STEREO PANEL SCHEMATIC
OCV TV PANEL SCHEMATIC
CARD INTERCONNECT PANEL
HEALTH CARE JACK PANEL
LODGING/SMART PORT PANEL
MAIN CHASSIS PCB (TOP)
MAIN CHASSIS PCB (BOTTOM)
13", 19", & 20" CRT PANEL PCB
25", & 27" CRT PANEL PCB
KEYBOARD/SOUND SHAPER PCB
STEREO PANEL PCB
OCV TV PANEL PCB (TOP)
OCV TV PANEL PCB (BOTTOM)
CARD INTERCONNECT PANEL PCB
HEALTH CARE JACK PANEL PCB
LODGING/SMART PORT PANEL PCB
8. Adjustments
10. Spare Parts List
Copyright 2001 Philips Consumer Electronics B.V. Eindhoven, The Netherlands.
All rights reserved. No part of this publication may be reproduced, stored in a
retrieval system or transmitted, in any form or by means, electronic, mechanical,
photographic, or otherwise without the prior permission of Philips.
©
Published by Philips Consumer Electronics Subject to modification 2005 Aug 24

20B8(7562)
1
3 Vp-p
50 uSec
2
3.2 Vp-p
20 uSec
3
1 Vp-p
20 uSec
4
5.6 Vp-p
5 mSec
5
4.9 Vp-p
20 uSec
6
50 Vp-p
5 mSec
7
800 mVp-p
5 mSec
8
2.7 Vp-p
5 mSec
9
400 mVp-p
5 mSec
10
29 Vp-p
5 mSec
11
1.5 Vp-p
5 mSec
12
2.2 Vp-p
20 uSec
13
2.2 Vp-p
20 uSec
14
2.2 Vp-p
20 uSec
15
3.5 Vp-p
20 uSec
16
3.6 Vp-p
5 mSec
17
450 mVp-p
5 mSec
18
750 mVp-p
5 mSec
19
5 Vp-p
20 uSec
20
4.2 Vp-p
20 uSec

20B8(7562)
21
1.2 Vp-p
20 uSec
22
220 mVp-p
0.5 uSec
23
1.2 Vp-p
20 uSec
24
1.2 Vp-p
20 uSec
25
1.2 Vp-p
20 uSec
26
1.4 Vp-p
20 uSec
27
2.5 Vp-p
20 uSec
28
1 Vp-p
20 uSec
29
1.4 Vp-p
20 uSec
30
2.5 Vp-p
20 uSec
31
2.5 Vp-p
20 uSec
32
1.6 Vp-p
20 uSec
33
120 Vp-p
20 uSec
34
1040 Vp-p(a)
20 uSec
35
1 Vp-p
20 uSec
36
1.8 Vp-p
20 uSec
37
2 Vp-p
20 uSec
38
110 Vp-p
20 uSec
39
110 Vp-p
20 uSec
40
850 mVp-p
5 mSec

20B8(7562)
41
110 Vp-p
20 uSec

B8 COLOR TV CHASSIS OVERVIEW
The B8 Series Chassis is the Statement (standard line) TV Set produced by Philips Consumer
Electronics Company for the 1997 model year. The B8 Chassis is used in TV Sets with 25, and
27 inch CRT's. The B8 Chassis is also used in Commercial TV Sets with 13, 19, 20, 25, and 27
inch CRT's. The chassis orientation is front to rear in the B8 design (sometimes called "North-
South"), because the chassis is longer in this direction than across. The B8 Tuning System
features 181 Channels with On-Screen Display. The main Tuning System includes the tuner
along with the Microcomputer IC and the 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, Mode Switches, and
Service/Factory Setup Data.
The chassis features a Very Large Scale Integration (VLSI) IC for TV signal processing. This IC
performs Video IF, Sound IF, AGC control, Horizontal Signal processing, Vertical Signal
processing, Horizontal/Vertical synchronization, and Chrominance/Luminance processing. The
On-Screen Graphics information is placed on the main signal within the TV Signal Processor. On-
Screen Graphics generation and Closed Caption decoding are processed within the
Microcomputer and the signals are sent to the TV Signal Processor. Automatic Volume Level
(AVL - called "SMART SOUND" by marketing) control from the Microcomputer is sent to the AVL
IC. The "Smart Sound" function is performed within IC720.
The B8 Chassis features a Switching Mode Power Supply for the main voltage source. A "HOT"
ground reference is used in the primary side of the power supply. A "COLD" (signal) ground from
the secondary of the power supply is used throughout the rest of the chassis. AN ISOLATION
TRANSFORMER IS REQUIRED WHEN DOING SERVICE ON ANY VERSION OF THE NEW
CHASSIS.

SIGNAL FLOW
The incoming TV RF signal is applied to the U/V Tuner via the Antenna RF Input. The 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 Pin 11 of the U/V Tuner to the SAW Filter, Y200. The SAW
Filter produces bandpass shaping for the IF signal before it is applied to the TV Signal Processor
Integrated Circuit, IC271, for processing. AGC (to the Tuner) and AFT (to the Microcomputer)
signals are developed within IC271 and then sent to the Tuning System for RF Amp gain control.
Sound IF signal processing for the B8 Chassis is performed by coupling the 4.5MHz Sound IF
signal from IC271, Pin 6, via a Buffer Amplifier, Q221, and 4.5MHz Band Pass Filter, Y220, into
IC271, Pin 1. Audio is output from Pin 15 in mono versions and applied to the Audio Amp Output
IC, IC730, to drive the speakers. For the stereo equipped sets, the detected baseband audio
signal exits IC271, Pin 15, and then enters the Stereo Decoder IC200. The Stereo Decoder has
Internal/External switching, via the control input on Pin 21, to allow either the detected baseband
audio or External Audio from another source to be routed through and exit to IC730 and IC740.
Composite video from IC271, Pin 6, is buffered by Q221 and then passed through a 4.5MHz
Trap, Y221, to remove any sound products present. This signal is buffered again by Q225 before
it goes back to IC271, Pin 13. Depending on the part number of IC271, either BS315 or BS316
will be installed. With BS315 installed, The CC Video comes from Q225. If BS316 is installed,
the CC Video comes from Pin 38 of IC271. Internal/External switching of the video is done within
IC271. The chroma and luminance signals are then processed by the Chroma/Luminance
Process block within IC271. Sync input from the Chroma/Luminance block to the

Horizontal/Vertical Processing block is applied internally within IC271.
Brightness, Picture, Sharpness, Color, and Tint control voltages are applied to IC271 from
Microcomputer, IC300 via the IIC Bus. The Red, Green, and Blue signals are developed within
IC271 and output via Pins 21, 20, and 19. The Black Current Level Set is Output from Pin 18.
The Red, Green, and Blue video signals from IC271 are applied to the CRT Board. On the CRT
Board, these signals are amplified before being applied to the CRT. The Drive and Cutoff
controls for CRT Set-Up are controlled by the microprocessor via the IIC Bus using the Service
Test Mode.
Horizontal and Vertical signals are also developed within IC271. Adjustments for Horizontal
Centering, Vertical Centering, and Vertical Height are accomplished 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.
The horizontal signal is applied to a Horizontal Driver, Q502, where the signal is amplified and
transformer coupled to the Horizontal Output transistor, Q503. The output from Q503 drives the
Integrated Flyback Transformer. The IFT develops the High Voltage, Screen Voltage, Focus
Voltage, and Filament Voltage for the Picture Tube. If the voltage in T501 (T502 for 25 and 27
inch sets) goes high, a sample is sent to Q540 and Q541, the shutdown switch. This will enable
lowering the High Voltage when it starts to elevate. Scan derived voltages provided by the IFT for
use by the chassis are the 200V, +1 3.5V, and -13.5V Sources. A horizontal pulse is also made
available for the chassis from the output circuit of the Horizontal Output transistor.
The Vertical signal exits TC271 at Pin 7 and is applied to the Vertical Output Integrated Circuit,
IC550. The vertical signal is output from IC550 and applied to the Vertical Yoke. Vertical
Centering and Vertical Height adjustments are performed via the Service Test Mode and Remote
Transmitter. Vertical feedback is returned to IC550, Pin 1.
B8 CHASSIS POWER SUPPLY BLOCK
When a 120Vac Source is connected to the B8 Chassis, approximately I60Vdc is developed by

the Bridge Rectifier circuit. The 160 volts dc goes through T425 to the transistor switch. The
start up signal is taken from the neutral leg of the input ac line.
The Power Supply consists of 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. The Power Supply turns On when AC is applied. The
Switching Regulator IC starts switching when the initial voltage is applied through the Start circuit.
The Switching Regulator and the Drive circuits turns the Switch On and Off to allow current flow
through the primary of transformer T425. 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 T425, the voltages needed to operate the television are developed. The
Plus 9 volt output is switched for On/Off control.

All Models (7562) - MAIN CHASSIS (SECTION 1 OF 5)

All Models (7562) - MAIN CHASSIS (SECTION 2 OF 5)