NOBLEX LA8A, 21TC677U, 21TC667U Service Manual

SERVICE MANUAL Colour Television

JXMRR

NOBLEX

FILE NO.

Model No. 21TC677U

(Argentina)

Service Ref. No. 21TC677U-00

Specifications

Power Source . . . . . . . . . AC220V, 50Hz / 60Hz

Receiving System . . . . . . PAL (M/M, N/N), NTSC (M/M)

Channel Coverage

Antenna mode VHF: CH02-CH13, UHF: CH14-CH69

CATV mode VHF band: CH01-CH13, Mid band: CH14-CH22

Super band: CH23-CH36, Hyper band: CH37-CH64
Ultra band: CH65-CH94 and CH100-CH125
Low mid band: CH95-CH99

Aerial Input Impedance . . 75Ω
Input Terminals
AV1 (Video): Phono jack ✕ 1
AV1 (Audio): Phono jack (R/L) ✕ 1 set
AV2 (Video): Phono jack ✕ 1
AV2 (Audio): Phono jack (R/L) ✕ 1 set
Output Terminals
Video Monitor Output: Phono jack ✕ 1
Audio Monitor Output: Phono jack (R/L) ✕ 1
Headphone Jack: Mini stereo jack ✕ 1

Sound Output (RMS) . . . . 3W + 3W

Speakers . . . . . . . . . . . 5cm x 9cm x 2 pcs.

Dimensions . . . . . . . . . 597(W) X 464.5(H) X 335(D) mm

Weight . . . . . . . . . . . . . approx. 20Kg

Specifications subject to change without notice.

BE2A

Product Code: 13015400

Original Version

Chassis Series: LA8-A

Give complete “SERVICE REF. NO.” for
parts order or servicing. It is shown on the
rating plate at the cabinet back of the unit.

This T.V. receiver will not work properly in
foreign countries where the television trans­mission system and power source differ from
the design specifications. Refer to the speci­fication table.

Contents

Safety Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Chassis Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

IC Block Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Service Adjustments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-17

Purity and Convergence Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Cabinet Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Chassis Electrical Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-26

Safety Notice

SAFETY PRECAUTIONS

1: An isolation transformer should be connected in the

power line between the receiver and the AC line
when a service is performed on the primary of the
converter transformer of the set.

2: Comply with all caution and safety-related notes

provided on the cabinet back, inside the cabinet, on
the chassis or the picture tube.

3: When replacing a chassis in the cabinet, always

be certain that all the protective devices are
installed properly, such as, control knobs, adjust­ment covers or shields, barriers, isolation resistor­capacitor networks etc.. Before returning any
television to the customer, the service techni­cian must be sure that it is completely safe
to operate without danger of electrical shock.

X-RADIATION PRECAUTION

The primary source of X-RADIATION in television receiver is the picture tube. The picture tube is specially con­structed to limit X-RADIATION emissions. For continued X-RADIATION protection, the replacement tube must
be the same type as the original including suffix letter. Excessive high voltage may produce potentially hazard­ous X - RADIATION. To avoid such hazards, the high voltage must be maintained within specified limit. Refer
to this service manual, high voltage adjustment for specific high voltage limit. If high voltage exceeds specified
limits, take necessary corrective action. Carefully follow the instructions for + B1 volt power supply adjustment,
and high voltage check to maintain the high voltage within the specified limits.

PRODUCT SAFETY NOTICE

Product safety should be considered when a component replacement is made in any area of a receiver.
Components indicated by mark in the parts list and the schematic diagram designate components in which

safety can be of special significance. It is particularly recommended that only parts designated on the parts list
in this manual be used for component replacement designated by mark . No deviations from resistance

wattage or voltage ratings may be made for replacement items designated by mark .

-2-

Chassis Block Diagrams

MAIN SIGNAL PROCESSING CIRCUIT

-3-

Chassis Block Diagrams

FUNCTIONAL BLOCK DIAGRAM

POWER SUPPLY IC601 (STRW6754)

-4-

IC Block Diagrams

IC201 < IF/Video/Chroma/Def./CPU > LA76933

-5-

IC Block Diagrams

IC501<Vertical.Output> LA78141

IC001<AUDIO AMP> LA42205

-6-

IC Block Diagrams

10 11 12

Slave Address = 80h ( 1000 000* ) :Pin8=OPEN/GND

Slave Address = 84h ( 1000 010* ) :Pin8=H

Vcc 5V

+

98

65 7

4

21 3

21

2324

22

15

14 13

161719

20

18

MATRIX

MODE

OUT

REGULATOR

+ ++

+

+

+

+

+

+

4.5M

BPF

LPF

SIF DEMOD

SAP BPF

SAP

DEMOD

L-R

DEMOD

ST/SAP

SW

LPF

-6dB

PILOT

CANCELLER

STEREO

PLL

PILOT

DET

PILOT

LEV EL DE T

IIC

DECODE

SYSTEM

CONTROL

Offset

Cancell

dbx processor

SAP

DET

4u7

4u7

22u

4u7

OUT(L) OUT(R)

MODE

Monitor

2u2

1u

1u

0.1?

1u

4k7

MUTE

L+R

L-R/SAP

ST

SAP

Address

Control

GND

MU TE

Wide RMS DET

Spectral DET

Spectral In

Offset Cancel

0.1u

0.1u

4u7

1u to

0.33u

SIF SIGNAL

from Tuner

Address

Control

IIC

DATA

IIC

CLOCK

2u2

22u

Spectral RMS

DET

100u

0.1u

47u

+

10u

+

10u

33n

33n

+

1u

+

560k

LPF

IC3401　LA72703

-7-

IC Block Diagrams

R2A15908SP

INR2

INR1

INL1

INL2

INL5

IGOUTL

VOLINL

VOLINR

BASSL1

INL3

INL4

IGOUTR

BASSR2

ROUT

LOUT

AGND

SDA

SCL

DGND

BASSL2

TRER

VCC

REFIN

BASSR1

INR4

INR3

INR5

28

27

26

25

24

23

22

21

20

19

1

2

3

4

5

6

7

8

9

10

18

17

11

12

Mode selector

Surround

REF

Input
selector

13

14

16

15

Tone control

Rch Bass/Treble

Volume

0~+20dB

/2dB step

Input
selector

0~-87dB,-∞

MCU

I/F

Input gain

control

mute

mute

Tone control

Lch Bass/Treble

Volume

0~-87dB,-∞

0~+20dB
/2dB step

Mono

/Stereo

TREL

IC3402 R2S15908SP

-8-

Service Adjustments

21-BE2F/BE2A/BE2J/BE2P

General

This set has an On-screen Service Menu system included in the CPU that allows remote operation for most of the
service adjustments.

IC802 (EEPROM) Replacement

When IC802 (EEPROM) is replaced, IC801 (CPU) will automatically write the initial reference data into IC802 for basic TV operation.
However, the bus data should be checked and some bus data should be set up before attempting the service adjustments. (See
pages 9 ~ 10 for detailed information.)

Service Adjustment-1

1. Enter the Service Menu
While pressing the MENU button on the television, press the Number Key 2 on the remote control unit.

The Service Menu now appear.

S1.11100101 S2.11111000
ADDRESS DATA
01 RFAGC 08

Item No.

Item

[ Service Mode Display ]

Data value

2. Service Adjustments:
Press the CHANNEL UP or CHANNEL DOWN

button on the remote control handset to select the

desired service menu item you want to adjust.

Use the

- button will increase or decrease the data
sequentially.

VOLUME + or - to adjust the data. The + or

VOLUME

MENU

CHANNEL UP

VOLUME +

-

CHANNEL DOWN

3. Exit from the Service Menu
Press the MENU button to turn off the Service Menu

display.
The data which is set in the service mode is stored
into the memory IC automatically.

MENU

-9--9-