philips_chassis_l7.2e_aa.pdf

Colour Television

Chassis

L7.2 AA

CL 86532008_004.ai

160298

Service Manual

Table of contents

Page

1 Technical specifications

Location of panels

2 Connection facilities

3 Safety instructions, Warnings

and Notes

4 Mechanical instructions

5 Repair facilities

Software adjustments

and Hotel mode

6 Fault finding tree

Block diagram,

Survey of testpoints

Diagram supply voltages survey

7 Electrical Diagrams and print lay-outs

Diagram PWB

Power supply

diagram A1

17,19

Sync, Horizontal + Vertical output diagram A2

17,19

Tuner, IF,Video,Chroma

diagram A3

17,19

Control

diagram A4

17,19

Sound processing, Sound interfacediagram A5 22

17,19

CRT panel

diagram B

Sound Multi-mono panel

diagram C

Sound Nicam-2CS panel

diagram D

8 Electrical adjustments

9 Circuit diagram description (new circuits)

10 Directions for use

11 List of abbreviations

12 Spareparts list

Published by FM 9863 TV Service Department

Printed in The Netherlands

Copyright reserved 1998 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 any means, electronic, mechanical, photocopying, or otherwise

without the prior permision of Philips.

Subject to modification

4822 727 21567

stored in a retrieval system or transmitted, in any form or by any means, electron-

ic, mechanical, photocopying, or otherwise without the prior permision of Philips.

Published by FM 9863 TV Service Department Printed in The Netherlands

Subject to modification

4822 727 21567

L7.2E

1 Technical specifications

Mains Voltage:

: 220 - 240 V AC

: (+/- 10%)

Power consumption

: 17” 50 W

: (stand by < 7 W)

: 21” 57 W

: (stand by < 7 W)

Pull in range colour sync

: +/- 300 Hz

Pull in range horizontal sync

: +/- 600 Hz

Pull in range vertical sync

: 45 - 64.5 Hz

Location of panels

MULTIMONO

CRT

AUDIO PANEL

NICAM,

MAIN

POWER SUPPLY

SYNCHRONISATION

HOR.DEFLECTION

VERT. DEFLECTION

TUNER IF

VIDEO PROCESSING

CONTROL

AUDIO SOURCE INPUT

AUDIO PROCESSING

CL 86532008_005.ai

260398

2 Connection facilities

L7.2E

Connection facilities

Video

(Ext2)

L R

Audio

Volume ++

Channel

Red

EXT1

CL86532008_008.ai

170298

2.1

Cinch

4.5-7V:EXT 16:9

- Video

1Vpp/75 W

9.5-12V:EXT 4:3

- Audio

L(0.5Vrms ³ 10k W )

9 - Green

- Audio

R(0.5Vrms ³ 10k W )

10-

11- Green

(0.7Vpp/75 W )

2.2

Head phone

12-

13- Red

(32-600 W³ 10mW)

14- RGB-

status

15- Red

(0.7Vpp/75 W )

2.3

Euroconnector

16- RGB-

status

(0-0.4V:INT

1-3V:EXT/75 W )

17- CVBS

18- CVBS

19- CVBS

(1Vpp/75 W )

1 - Audio

R (0.5Vrms

)

20- CVBS

(1Vpp/75 W )

2 - Audio

R (0.5Vrms

10k

)

21- Earth

socket

3 - Audio

L (0.5Vrms

)

4 - Audio

5 - Blue

6 - Audio

L (0.5Vrms

10k

)

7 - Blue

(0.7Vpp/75

)

8 - CVBS-

status

0-1.3V:INT

L7.2E

3 Safety instructions, Maintenance instruction,

3.1

Safety instructions for repairs

– When the set is used in circumstances with higher dust,

grease or moisture levels, for example in a kitchen, the

recommended interval is 1 year.

– The maintenance inspection contains the following actions:

• Execute the above mentioned 'general repair

instruction'.

• Clean the power supply and deflection circuitry on the

chassis.

• Clean the picture tube panel and the neck of the picture

tube.

Figure 3-1

1. Safety regulations require that during a repair:

– the set should be connected to the mains via an

isolating transformer;

– safety components, indicated by the symbol (see fig.

3.1), should be replaced by components identical to

the original ones;

– when replacing the CRT, safety goggles must be worn.

3.3

Warnings

2. Safety regulations require that after a repair the set must

be returned in its original condition. In particular attention

should be paid to the following points.

– As a strict precaution, we advise you to resolder the

solder joints through which the horizontal deflection

current is flowing, in particular:

• all pins of the line output transformer (LOT);

• fly-back capacitor(s);

• S-correction capacitor(s);

• line output transistor;

• pins of the connector with wires to the deflection

coil;

• other components through which the deflection

current flows.

1. ESD

All ICs and many other semiconductors are susceptible to

electrostatic discharges (ESD). Careless handling during

repair can reduce life drastically. When repairing, make

sure that you are connected with the same potential as the

mass of the set by a wristband with resistance. Keep

components and tools also at this same potential.

– Available ESD protection equipment:

– anti-static table mat (large 1200x650x1.25mm) 4822

466 10953

– anti-static table mat (small 600x650x1.25mm) 4822

466 10958

– anti-static wristband 4822 395 10223

– connection box (3 press stud connections, 1 M ohm)

4822 320 11307

– extension cable (2 m, 2 M ohm; to connect wristband

to connection box) 4822 320 11305

– connecting cable (3 m, 2 M ohm; to connect table mat

to connection box) 4822 320 11306

– earth cable (1 M ohm; to connect any product to mat or

connection box) 4822 320 11308

– complete kit ESD3 (combining all 6 prior products -

small table mat) 4822 310 10671

– wristband tester 4822 344 13999

Note: This resoldering is advised to prevent bad

connections due to metal fatigue in solder joints and is

therefore only necessary for television sets older than

2 years. The wire trees and EHT cable should be

routed correctly and fixed with the mounted cable

clamps.

– The insulation of the mains lead should be checked for

external damage.

– The mains lead strain relief should be checked for its

function in order to avoid touching the CRT, hot

components or heat sinks.

– The electrical DC resistance between the mains plug

and the secondary side should be checked (only for

sets which have a mains isolated power supply). This

check can be done as follows:

• unplug the mains cord and connect a wire between

the two pins of the mains plug;

• set the mains switch to the on position (keep the

mains cord unplugged!);

• measure the resistance value between the pins of

the mains plug and the metal shielding of the tuner

or the aerial connection on the set. The reading

should be between 4.5 MW and 12 MW;

• switch off the TV and remove the wire between the

two pins of the mains plug.

2. In order to prevent damage to ICs and transistors, all high-

voltage flashovers must be avoided. In order to prevent

damage to the picture tube, the method shown in Fig. 3.2

should be used to discharge the picture tube. Use a high-

voltage probe and a multimeter (position DC-V). Discharge

until the meter reading is 0V (after approx. 30s).

3. Together with the deflection unit and any multipole unit, the

flat square picture tubes used from an integrated unit. The

deflection and the multipole units are set optimally at the

factory. Adjustment of this unit during repair is therefore not

recommended.

4. Be careful during measurements in the high-voltage

section and on the picture tube.

5. Never replace modules or other components while the unit

is switched on.

6. When making settings, use plastic rather than metal tools.

This will prevent any short circuits and the danger of a

circuit becoming unstable.

7. Wear safety goggles during replacement of the picture tube

– The cabinet should be checked for defects to avoid

touching of any inner parts by the customer.

3.2

Maintenance instruction

3.4

Notes

It is recommended to have a maintenance inspection carried

out by a qualified service employee. The interval depends on

the usage conditions:

1. The direct voltages and oscillograms should be measured

with regard to the tuner earth , or hot earth as this is called

(see fig. 3.3)

2. The direct voltages and oscillograms shown in the

diagrams are indicative and should be measured in the

Service Default Mode (see chapter 8) with a colour bar

signal and stereo sound (L:3 kHz, R:1 kHz unless stated

otherwise) and picture carrier at 475.25 MHz.

– When the set is used under normal circumstances, for

example in a living room, the recommended interval is 3 to

5 years.

Safety instructions, Maintenance instruction, Warnings and Notes

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