Digital Equipment 14BM18 Service Manual

FILE NO. SM-CTV-O-158

COLOR TELEVISION

SERVICE MANUAL

MODEL NO. 14BM18

CHASSIS NO. EX-1A3

Please read this manual carefully before service

TABLE OF CONTENTS

SPECIFICATIONS··················································································································1

SAFETY INSTRUCTIONS AND MAINTENANCE········································2

X-RAY RADIATION PRECAUTION ···································································································2

SAFETY PRECAUTION ····················································································································

PRODUCT SAFETY NOTICE ···········································································································

SAFETY SYMBOL DESCRIPTION ···································································································

MAINTENANCE·································································································································

ADJUSTMENTS

······················································································································

SET-UP ADJUSTMENTS ··················································································································5

CIRCUIT ADJUSTMENTS·················································································································

STRUCTURE AND CHASSIS FUNCTION DESCRIPTION

···············

STRUCTURE BLOCK DIAGRAM··································································································· 15

BLOCK DIAGRAM FOR SUPPLY VOLTAGE SYSTEM·································································

CHASSIS DESCRIPTION···············································································································

SERVICE DATA···················································································································· 18

TECHNICAL DATA OF KEY ICS ···································································································· 18

WAVEFORMS OF KEY POINTS ····································································································

SERVICE DATA OF KEY ICS·········································································································

REPLACEMENT OF PARTS ··········································································································

APPENDIX

1. CIRCUIT DIAGRAM

2. PRINTED CIRCUIT BOARD DIAGRAMS

3. FINAL WIRING DIAGRAM

4. FINAL ASSEMBLY DIAGRAM

SERVICE MANUAL

SPECIFICATIONS

Model Number 14BM18

Color system

PAL4.43, NTSC3.58, NTSC4.43, SECAM

RF system

Sound system B/G, I, M, D/K

VHF

C12 (49.75-85.25MHz, 168.25-216.25MHz)

UHF

C13

C57 (471.25-863.25MHz)

Receiving

channel

CATV

Z7 (111-167MHz)

Z35 (223-447MHz)

Programs preset 236(0-235)

Antenna input

(unbalanced)

Picture tube (Approx.)

Effective screen dimensions

280

210mm

Audio output (THD 7%)

Power source 110-240V ~, 50/60Hz

Weight (Approx.) 10.5kg

Dimensions

H D) (Approx.)

416

332 390mm

Rated power consumption 69W

Note: Designs and specifications are subject to change without notice.

SERVICE MANUAL

INSTRUCTIONS FOR SERVICE SAFETY AND MAINTENANCE

WARNING: BEFORE SERVICING THIS CHASSIS, READ THE X-RA Y RADIATION PRECAUTION ,

SAFETY PRECAUTION AND PRODUCT SAFETY NOTICE INSTRUCTION BELOW.

X-RAY RADIATION PRECAUTION

1. The EHT must be checked every time the TV is serviced to ensure that the CRT does not emit

X-ray radiation as result of excessive EHT voltage. The maximum EHT voltage permissible in any

operating circumstances must not exceed the rated value. When checking the EHT, use the High

Voltage Check procedure in this manual using an accurate EHT voltmeter.

2. The only source of X-RAY radiation in this TV is the CRT. The TV minimizes X-RAY radiation, which

ensures safety during normal operation. To prevent X-ray radiation, the replacement CRT must be

identical to the original fitted as specified in the parts list.

3. Some components used in this TV have safety related characteristics preventing the CRT from

emitting X-ray radiation. For continued safety, replacement component should be made after

referring the PRODUCT SAFETY NOTICE below.

4. Service and adjustment of the TV may result in changes in the nominal EHT voltage of the CRT

anode. So ensure that the maximum EHT voltage does not exceed the rated value after service

and adjustment.

SAFETY PRECAUTION

WARNING: REFER SERVICING TO QUALIFIED SERVICE PERSONNEL ONLY.

1. The TV has a nominal working EHT voltage. Extreme caution should be exercised when working

on the TV with the back removed.

1.1 Do not attempt to service this TV if you are not conversant with the precautions and procedures for

working on high voltage equipment.

1.2 When handling or working on the CRT, always discharge the anode to the TV chassis before

removing the anode cap in case of electric shock.

1.3 The CRT, if broken, will violently expel glass fragments. Use shatterproof goggles and take extreme

care while handling.

1.4 Do not hold the CRT by the neck as this is a very dangerous practice.

2. It is essential that to maintain the safety of the customer all power cord forms be replaced exactly

as supplied from factory.

3. Voltage exists between the hot and cold ground when the TV is in operation. Install a suitable

isolating transformer of beyond rated overall power when servicing or connecting any test

equipment for the sake of safety.

4. When replacing ICs, use specific tools or a static-proof electric iron with small power (below 35W).

SERVICE MANUAL

5. Do not use a magnetized screwdriver when tightening or loosing the deflection yoke assembly to

avoid electronic gun magnetized and decrement in convergence of the CRT.

6. When remounting the TV chassis, ensure that all guard devices, such as nonmetal control buttons,

switch, insulating sleeve, shielding cover, isolating resistors and capacitors, are installed on the

original place.

7. Replace blown fuses within the TV with the fuse specified in the parts list.

8. When replacing wires or components to terminals or tags, wind the leads around the terminal

before soldering. When replacing safety components identified by the international hazard symbols

on the circuit diagram and parts list, it must be the company-approved type and must be mounted

as the original.

9. Keep wires away from high temperature components.

PRODUCT SAFETY NOTICE

CAUTION: FOR YOU PROTECTION, THE FOLLOWING PRODUCT SAFETY NOTICE SHOULD BE READ CAREFULLY BEFORE OPERATING AND SERVICING THIS TV SET.

1. Many electrical and mechanical components in this chassis have special safety-related

characteristics. These characteristics are often passed unnoticed by a visual inspection and the

X-ray radiation protection afforded by them cannot necessarily be obtained by using replacements

rated at higher voltages or wattage, etc. Components which have these special safety

characteristics in this manual and its supplements are identified by the international hazard

symbols on the circuit diagram and parts list. Before replacing any of these components read the

parts list in this manual carefully. Substitute replacement components which do not have the same

safety characteristics as specified in the parts list may create X-ray radiation.

2. Do not slap or beat the cabinet or CRT, since this may result in fire or explosion.

3. Never allow the TV sharing a plug or socket with other large-power equipment. Doing so may result

in too large load, causing fire.

4. Do not allow anything to rest on or roll over the power cord. Protect the power cord from being

walked on, modified, cut or pinched, particularly at plugs.

5. Do not place any objects, especially heavy objects and lightings, on top of the TV set. Do not install

the TV near any heat sources such as radiators, heat registers, stove, or other apparatus that

produce heat.

6. Service personnel should observe the SAFETY INSTRUCTIONS in this manual during use and

servicing of this TV set. Otherwise, the resulted damage is not protected by the manufacturer.

SAFETY SYMBOL DESCRIPTION

The lightning symbol in the triangle tells you that the voltage inside this product may be

strong enough to cause an electric shock. Extreme caution should be exercised when

SERVICE MANUAL

working on the TV with the back removed.

This is an international hazard symbol, telling you that the components identified by the

symbol have special safety-related characteristics.

FDA

This symbol tells you that the critical components identified by the FDA marking have

special safety-related characteristics.

This symbol tells you that the critical components identified by the UL marking have

special safety-related characteristics.

C UL

This symbol tells you that the critical components identified by the C-UL marking have

been evaluated to the UL and C-UL standards and have special safety-related

characteristics.

VDE

This symbol tells you that the critical components identified by the VDE marking have

special safety-related characteristics.

MAINTENANCE

1. Install the TV set on a stable and level surface. Do not place the set near or over a radiator or heat

2. Do not install the TV set in a place exposed to rain, water, excessive dust, mechanical vibrations or

impacts.

3. Allow enough space (at least 10cm) between the TV and wall or enclosures for proper ventilation.

4. Slots and openings in the cabinet should never be blocked by clothes or other objects.

5. Please power off the TV set and disconnect it from the wall immediately if any abnormal condition

are met, such as bad smell, belching smoke, sparkling, abnormal sound, no picture/sound/raster.

Hold the plug firmly when disconnecting the power cord.

6. Unplug the TV set from the wall outlet before cleaning or polishing it. Use a dry soft cloth for

cleaning the exterior of the TV set or CRT screen. Do not use liquid cleaners or aerosol cleaners.

SERVICE MANUAL

ADJUSTMENTS

SET-UP ADJUSTMENTS

The following adjustments should be made when a complete realignment is required or a new picture

tube is installed.

Perform the adjustments in the following order:

1. Color purity

2. Convergence

3. White balance

Notes:

The purity/convergence magnet assembly and rubber wedges need mechanical positioning. For some picture tubes, purity/ convergence adjustments are not required.

1. Color Purity Adjustment

Preparation:

Before starting this adjustment, adjust the vertical sync, horizontal sync, vertical amplitude and

focus.

1.1 Face the TV set north or south.

1.2 Connect the power plug into the wall outlet and turn on the main power switch of the TV set.

1.3 Operate the TV for at least 15 minutes.

1.4 Degauss the TV set using a specific degaussing coil.

1.5 Set the brightness and contrast to maximum.

1.6 Counter clockwise rotate the R/B low brightness potentiometers to the end and rotate the green low

brightness potentiometer to center.

1.7 Receive green raster pattern signals.

1.8 Loosen the clamp screw holding the deflection yoke assembly and slide it forward or backward to

display a vertical green zone on the screen. Rotate and spread the tabs of the purity magnet

around the neck of the CRT until the green zone is located vertically at the center of the screen.

1.9 Slowly move the deflection yoke assembly forward or backward until a uniform green screen is

obtained.

1.10 Tighten the clamp screw of the assembly temporarily. Check purity of the red raster and blue raster

until purities of the three rasters meet the requirement.

SERVICE MANUAL

Fig. 1

2. Convergence Adjustment

Preparation:

Before attempting any convergence adjustment, the TV should be operated for at least 15 minutes.

2.1 Center convergence adjustment

2.1.1 Receive dot pattern.

2.1.2 Adjust the brightness/contrast controls to obtain a sharp picture.

2.1.3 Adjust two tabs of the 4-pole magnet to change the angle between them and red and blue

vertical lines are superimposed each other on the center of the screen.

2.1.4 Turn both tabs at the same time keeping the angle constant to superimpose red and blue

horizontal on the center of the screen.

2.1.5 Adjust two tabs of the 6-pole magnet to superimpose red/blue line and green line.

2.1.6 Remember red and blue movement. Repeat steps2.1.3-2..1.5 until optimal convergence is

Deflection Coil

Dummy Wedge

Rubber Wedge

Adhesive

Deflection Yoke

Purity/Convergence Ma

net Module

Glass Cloth Tapes

6-pole Magnet

Adj

ust the Angle (Vertical Lines

)

Fixed

Rotate Two Tabs At the Same Time

(

Horizontal Lines

)

Adjustment of Magnets

Purity Magnet

Conver

ence Magnet Assembl

4-pole Magnet

Fig. 2

SERVICE MANUAL

Incline the Yoke up (or down) Incline the Yoke Right(or left)

Circumference Convergence by DEF Yoke

Fig. 3

obtained.

2.2 Circumference convergence adjustment

2.2.1 Loosen the clamp screw holding the deflection yoke assembly and allow it tilting.

2.2.2 Temporarily put the first wedge between the picture tube and deflection yoke assembly. Move

front of the deflection yoke up or down to obtain better convergence in circumference. Push the

mounted wedge in to fix the yoke temporarily.

2.2.3 Put the second wedge into bottom.

2.2.4 Move front of the deflection yoke to the left or right to obtain better convergence in

circumference.

2.2.5 Fix the deflection yoke position and put the third wedge in either upper space. Fasten the

deflection yoke assembly on the picture tube.

2.2.6 Detach the temporarily mounted wedge and put it in either upper space. Fasten the deflection

yoke assembly on the picture tube.

2.2.7 After fastening the three wedges, recheck overall convergence and ensure to get optimal

convergence. Tighten the lamp screw holding the deflection yoke assembly.

3. White Balance Adjustment

Generally, white balance adjustment is made with professional equipment. It’s not practical to get

good white balance only through manual adjustment. For TVs with I

C bus control, change the bus

data to adjust white balance.

BLU Red Red/BLU

BLU

Red

4-pole Magnet Movement 6-pole Magnet

Movement

Red/BL

SERVICE MANUAL

CIRCUIT ADJUSTMENTS

Preparation:

Circuit adjustments should be made only after completion of set-up adjustments.

Circuit adjustments can be performed using the adjustable components inside the TV set. For TVs with

C bus control, first change the bus data.

1. Degaussing

A degaussing coil is built inside he TV set. Each time the TV is powered on, the degaussing coil will

automatically degauss the TV. If the TV is magnetized by external strong magnetic field, causing

color spot on the screen, use a specific degausser to demagnetize the TV in the following ways.

Otherwise, color distortion will be shown on the screen.

1.1 Power on the TV set and operate it for at least 15 minutes.

1.2 Receive red full-field pattern.

1.3 Power on the specific degausser and face it to the TV screen.

1.4 Turn on the degausser. Slowly move it around the screen and slowly take it away from the TV.

1.5 Repeat the above steps until the TV is degaussed completely.

2. Supply Voltage Adjustment

Caution: +B voltage has close relation to high voltage. To prevent X-ray radiation, set +B voltage to the rated voltage.

2.1 Make sure that the supply voltage is within the range of the rated value.

2.2 Connect a digital voltmeter to the +B voltage output terminal of the TV set. Power on the TV and set

the brightness and sub-brightness to minimum.

2.3 Regulate voltage adjustment components on the power PCB to make the voltmeter read 115±1V.

3. High Voltage Inspection

Caution: No high voltage adjustment components inside the chassis. Please perform high voltage inspection in the following ways.

3.1 Connect a precise static high voltmeter to the second anode (inside the high voltage cap) of the

picture tube.

3.2 Plug in the supply socket (110-240V, AC, 50/60Hz) and turn on the TV. Set the brightness and

contrast to minimum (0

A).

3.3 The high voltage reading should be less than the EHT limitation.

3.4 Change the brightness from minimum to maximum, and ensure high voltage not beyond the

limitation in any case.

Nominal EHT voltage: 22

1.3KV Limited EHT voltage: 25KV

4. Focus Adjustment

Caution: Dangerously high voltages are present inside the TV. Extreme caution should be exercised when working on the TV with the back removed.

4.1 After removing the back cover, look for the FBT on the main PCB. There should be a FCB on the

SERVICE MANUAL

VS 0-3F 25

xxxxxxxx

FBT.

4.2 Power on the TV and preheat it for 15 min.

4.3 Receive a normal TV signal. Rotate knob of the FCB until you get a sharp picture.

5. Safety Inspection

5.1 Inspection for insulation and voltage-resistant

Perform safety test for all naked metal of the TV. Supply high voltage of 3000V AC, 50Hz (limit

current of 10mA) between all naked metal and cold ground. Test every point for 3 min. and ensure

no arcing and sparking.

5.2 Requirements for insulation resistance

Measure resistance between naked metal of the TV and feed end of the power cord to be infinity

with a DC-500 high resistance meter and insulation resistance between the naked metal and

degaussing coil to be over 20M

6. DESIGN/SERVICE mode

6.1 To enter the USER SERVICE mode

Caution: The user service mode adjustment can be changed only when service personnel adjust

the whole set data during servicing. As the control data have dramatic effects on functions and

performance of the TV, service personnel should not tell user how to

enter the SERVICE mode to avoid improper data settings.

6.1.1 Set the volume to 0. Then press and hold the MUTE button on

the remote control, and press the MENU button on the TV to

enter the SERVICE mode. (In this case, the S mode cannot be

stored in the EEPROM. To exit from the S mode, turn off the TV set. )

6.1.2 After entering the S mode, Red

S is displayed on the upper center of the screen and MENU1

is default. Use the POS+/- buttons to highlight an adjustment and the VOL+/- buttons to adjust

it. The adjusted data are immediately output and stored in the EEPROM

6.2 Bus data in the S mode

Table 1 Adjustment and Option Data in S mode

Item Adjustment Description Remarks

CORE 03 Coring (for some CPU only)

0-IF 20 Sound adjustment setting (for some CPU only)

5PAR/6P

1F Parallelogram correction (for large-screen only)

5BOW/6

BOW

1F Curve correction (for large-screen only)

(continued)

SERVICE MANUAL

5HSH/6H

Set to the

optimal mode

Horizontal center in the TV mode for 50Hz/60Hz

For 50Hz,

5HSH is displayed for 60Hz, 6HSH

is displayed.

5EWW/6

EWW

1F East-West correction (for large-screen only)

5EWP/6

EWP

East-West parabola correction (for large-screen

only)

5UCR/6

UCR

Upper corner parabola correction (for large-screen

only)

5LCR/6L

Lower corner parabola correction (for large-screen

only)

5EWT/6

EWT

1F Trapezoidal correction (for large-screen only)

5VSL/6V

1F Vertical slope (for large-screen only) *

5VAM/6V

Vertical amplitude; For 50Hz,

5VAM is

displayed

for 60Hz, 6VAM is displayed.

5SCL/6S

Set to the

optimal mode

S correction *

5VSH/6V

Set to the

optimal mode

Vertical center in the TV mode for 50Hz/60Hz. For

50Hz,

5VSH is displayed for 60Hz, 6VSH

is displayed.

5VOF/6V

Set to the

optimal mode

OSD vertical center *

VX 19 Vertical zoom (for large-screen only)

RED 20 Red gun cutoff voltage *

GRN 20 Green gun cutoff voltage *

WPR 1F Red gun drive voltage *

WPG 1F Green gun drive voltage *

WPB 1F Blue gun drive voltage *

YDFP/Y

DFN

PAL brightness delay time/ NTSC brightness delay

time

TOP 10-1F UOC AGC *

VOL 26

TV audio output power can be adjusted by means of

UOC audio output amplitude. Generally, UOC audio

output amplitude is set to 26 for 21” models with

stereo output of 3W+3W; 2C for 21” models with

stereo output of 5W+5W; 24 for 14” models with

mono output of 2WX2; 22 for 14” models with mono

output of 1WX2.

***

(continued)

SERVICE MANUAL

IFFS

PIF (02-38.9MHz, 03-38MHz)

HDOL 00-07 Cathode drive level (typical: 04-07)

AGC 03 IF ACG speed

VG2B 3A

VG2 brightness setting(VG2B): 3A for 21” models;

2E for 14” models;

Contrast Max. setting (MCON): 30 for 21” Malaysia

Matsushita or BMCC CRT with ferrite mask;

MCON: 30; VG2B: 30, HDOL: 04 for 21” Chunghwa

CRT

SBRI 1F Sub brightness

MBRI 30 Brightness Max.

SCON 20 Sub contrast

MCON 39 Contrast Max.

SCOL 32 Sub color

OP1 87 Option set byte 1 ***

OP2 01 Option set byte 2 ***

OP3 FF Option set byte 3 ***

OP4 F6 Option set byte 4 ***

OP5 76 Option set byte 5 ***

OP6 1C Option set byte 6 ***

INIT EEPROM initialization

VG2 Adjusting screen voltage with VG2 *

VSD Vertical output off

STS0/1/2 System status byte

Notes:

The data marked with

* have been adjusted in the MANUFACTURE mode. Take care when in

service and adjustment.

To write in logo, use the

/ buttons to highlight an adjustment and the / buttons to adjust.

The data sheet may differ dependent on different models. The data sheet may differ dependent on different CRTs for the same model.

6.3 Option set

With remote control system software TDA935X, all options can be set in the SERVICE mode and

stored in EEPROM. Data related to picture, sound and geometric adjustment are also stored in

EEPROM.

+ 29 hidden pages

Digital Equipment 14BM18 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual