JVC AV-21AT Service Manual

SERVICE MANUAL

COLOUR TELEVISION

AV-21AT

BASIC CHASSIS

+−

−

CONTENTS

■ SPECIFICATIONS ........................................................................................................................... 2

■ SAFETY PRECAUTIONS ................................................................................................................ 3

■ FEATURES ...................................................................................................................................... 4

★ OPERATING INSTRUCTIONS (APPENDED).............................................................................. 1-1

■ SPECIFIC SERVICE INSTRUCTIONS ............................................................................................ 4

■ SERVICE ADJUSTMENTS............................................................................................................10

★ STANDARD CIRCUIT DIAGRAM (APPENDED) ......................................................................... 2-1

■ PARTS LIST................................................................................................................................... 27

No. 56013 1

No. 56013

May 2000

A V-21AT

SPECIFICATIONS

Item Content

Dimensions (W × H × D) 502mm × 451mm × 480.5mm Mass 19.5kg TV RF System B / G, I, D / K, K1 Colour System TV Mode PAL / SECAM

VIDEO Mode PAL / SECAM / NTSC3.58 / NTSC4.43

Receiving Frequency VHF (VL) 46.25MHz ~ 168.25MHz

VHF (VH) 175.25MHz ~ 463.25MHz UHF 471.25MHz ~ 863.25MHz CATV ● Cable TVs of Mid (X-Z, S1-S10)

Super (S11-S20) & Hyper (S21-S41) bands receivable

Intermediate VIF Carrier 38.0MHz Frequency 31.5MHz (6.5MHz)

SIF Carrier 32.0MHz (6.0MHz)

32.5MHz (5.5MHz)

33.5MHz (4.5MHz)

Colour Sub Carrier Frequency PAL (4.43MHz)

SECAM (4.40625MHz / 4.25MHz) NTSC (3.58MHz / 4.43MHz)

Aerial Input Terminal 75Ω Unbalanced Power Input AC110 ~ 240V, 50 / 60Hz Power Consumption 105W (Max.)/68W (Avg.) Picture Tube Visible size : 51cm measured diagonally High Voltage 26.5kV ± 1.5kV (at zero beam current) Speaker 5cm × 9 cm Oval type × 2 Audio Output 5W (Monaural) Input Video 1Vp-p, 75Ω

Audio 500mVrms (−4dBs), High impedance

Output Video 1Vp-p, 75Ω

Audio 500mVrms (–4dBs), Low impedance

Headphone Jack Stereo mini jack (3.5ø) Remote Control Unit RM-C364-1H (Battery size : AA/R06/UM-3 × 2)

Design & specifications are subject to change without notice.

No. 560132

SAFETY PRECAUTIONS

AC VOLTMETER (HAVING 1000Ω/V, OR MORE SENSITIVITY)

PLACE THIS PROBE ON EACH EXPOSED METAL PART

1500Ω 10W

0.15µF AC-TYPE

GOOD EARTH GROUND

AV-21AT

1. The design of this product contains special hardware, many circuits and components specially for safety purposes. For continued protection, no changes should be made to the original design unless authorized in writing by the manufacturer. Replacement parts must be identical to those used in the original circuits. Service should be performed by qualified personnel only.

2. Alterations of the design or circuitry of the products should not be made. Any design alterations or additions will void the manufacturer's warranty and will further relieve the manufacturer of responsibility for personal injury or property damage resulting therefrom.

3. Many electrical and mechanical parts in the products have special safety-related characteristics. These characteristics are often not evident from visual inspection nor can the protection afforded by them necessarily be obtained by using replacement components rated for higher voltage, wattage, etc. Replacement parts which have these special safety characteristics are identified in the parts list of Service manual. Electrical

components having such features are identified by shading on the schematics and by (!) on the parts list in Service manual. The use of a substitute replacement which does

not have the same safety characteristics as the recommended replacement part shown in the parts list of Service manual may cause shock, fire, or other hazards.

4. Don't short between the LIVE side ground and ISOLATED

(NEUTRAL) side ground or EARTH side ground when repairing.

Some model's power circuit is partly different in the GND. The difference of the GND is shown by the LIVE : (#) side GND, the ISOLATED (NEUTRAL) : (") side GND and EARTH : ($) side GND. Don't short between the LIVE side GND and ISOLATED (NEUTRAL) side GND or EARTH side GND and never measure with a measuring apparatus (oscilloscope etc.) the LIVE side GND and ISOLATED (NEUTRAL) side GND or EARTH side GND at the same time. If above note will not be kept, a fuse or any parts will be broken.

5. If any repair has been made to the chassis, it is recommended that the B1 setting should be checked or adjusted (See ADJUSTMENT OF B1 POWER SUPPLY).

6. The high voltage applied to the picture tube must conform with that specified in Service manual. Excessive high voltage can cause an increase in X-Ray emission, arcing and possible component damage, therefore operation under excessive high voltage conditions should be kept to a minimum, or should be prevented. If severe arcing occurs, remove the AC power immediately and determine the cause by visual inspection (incorrect installation, cracked or melted high voltage harness, poor soldering, etc.). To maintain the proper minimum level of soft XRay emission, components in the high voltage circuitry including the picture tube must be the exact replacements or alternatives approved by the manufacturer of the complete product.

8. When service is required, observe the original lead dress. Extra precaution should be given to assure correct lead dress in the high voltage circuit area. Where a short circuit has occurred, those components that indicate evidence of overheating should be replaced. Always use the manufacturer's replacement components.

9. Isolation Check

(Safety for Electrical Shock Hazard)

After re-assembling the product, always perform an isolation check on the exposed metal parts of the cabinet (antenna terminals, video/audio input and output terminals, Control knobs, metal cabinet, screw heads, earphone jack, control shafts, etc.) to be sure the product is safe to operate without danger of electrical shock.

(1) Dielectric Strength Test

The isolation between the AC primary circuit and all metal parts exposed to the user, particularly any exposed metal part having a return path to the chassis should withstand a voltage of 3000V AC (r.m.s.) for a period of one second.

(. . . . Withstand a voltage of 1100V AC (r.m.s.) to an appliance

rated up to 120V, and 3000V AC (r.m.s.) to an appliance rated 200V or more, for a period of one second.) This method of test requires a test equipment not generally found in the service trade.

(2) Leakage Current Check

Plug the AC line cord directly into the AC outlet (do not use a line isolation transformer during this check.). Using a "Leakage Current Tester", measure the leakage current from each exposed metal part of the cabinet, particularly any exposed metal part having a return path to the chassis, to a known good earth ground (water pipe, etc.). Any leakage current must not exceed

0.5mA AC (r.m.s.). However, in tropical area, this must not exceed 0.2mA AC (r.m.s.).

● Alternate Check Method Plug the AC line cord directly into the AC outlet (do not use a line isolation transformer during this check.). Use an AC voltmeter having 1000 ohms per volt or more sensitivity in the following manner. Connect a 1500Ω 10W resistor paralleled by a

0.15µF AC-type capacitor between an exposed metal part and a known good earth ground (water pipe, etc.). Measure the AC voltage across the resistor with the AC voltmeter. Move the resistor connection to each exposed metal part, particularly any exposed metal part having a return path to the chassis, and measure the AC voltage across the resistor. Now, reverse the plug in the AC outlet and repeat each measurement. Any voltage measured must not exceed 0.75V AC (r.m.s.). This corresponds to 0.5mA AC (r.m.s.). However, in tropical area, this must not exceed 0.3V AC (r .m.s.). This corresponds to 0.2mA AC (r.m.s.).

7. Do not check high voltage by drawing an arc. Use a high voltage meter or a high voltage probe with a VTVM. Discharge the picture tube before attempting meter connection, by connecting a clip lead to the ground frame and connecting the other end of the lead through a 10kΩ 2W resistor to the anode button.

No. 56013 3

A V-21AT

FEATURES

● New chassis design enables use of an interactive on-screen control.

● Wide range voltage for AC power input.

● With AUDIO / VIDEO INPUT & OUTPUT terminals.

● MUTING button can reduce the audio level to zero instantly.

● Functional remote control to operate TV set (for channel select, volume control, power ON/OFF, etc.) from a distance.

C bus control utilizes single chip ICs for IF, V/C (Video/Chroma) and VSM (Video Status Memory).

● I

● By means of AUTO PROGRAM, the TV stations can be selected automatically and the TV channels can also be rearranged

automatically.

● Built-in ECO MODE (ECONOMY, ECOLOGY) In accordance with the brightness in a room, the brightness and/or contrast of the picture can be adjusted automatically to make the optimum picture which is easy on the eye.

● Built-in ON TIMER & RETURN +.

SPECIFIC SERVICE INSTRUCTIONS

DISASSEMBLY PROCEDURE

REMOVING THE REAR COVER

1. Unplug the AC power cord.

2. Remove the 6 screws marked "A" and 1 screw marked "B".

3. Withdraw the rear cover backward.

REMOVING THE MAIN PW BOARD

● After removing the rear cover.

1. Slightly raise both sides of the Main PW Board by hand and

withdraw the Main PW Board backward. (If necessary, take off the wire clamp, connectors etc.)

REMOVING THE SPEAKER

● After removing the rear cover and the Main PW Board.

1. Remove the 2 screws marked "C".

2. Follow the same step for removing the other hand speaker.

CHECKING THE MAIN PW BOARD

T o check the back side of the Main PW Board, follow the next steps.

1. Pull out the Main PW Board. (Refer to "REMOVING THE MAIN

PW BOARD".)

2. Erect the Main PW Board vertically so that you can easily check

the back side of it.

CAUTION:

● When erecting the Main PW Board, be careful so that there will

be no contacting with other PW Board.

● Before turning on power, make sure that the CRT earth wire

and other connectors are properly connected.

WIRE CLAMPING AND CABLE TYING

1. Be sure to clamp the wire.

2. Never remove the cable tie used for tying the wires together.

Should it be inadvertently removed, be sure to tie the wires with a new cable tie.

No. 560134

FRONT CABINET

SPEAKER

CRT SOCKET PWB (Within MAIN PWB)

(×2)

MAIN PWB

AV-21AT

SPEAKER

REAR COVER

(×2)

(×6)

No. 56013 5

A V-21AT

REPLACEMENT OF MEMORY IC

1. MEMORY IC

This TV uses the following memory IC.

Memory IC: IC1702 on MAIN PW Board

The memory IC memorizes data for correctly operating the video and deflection circuits. When replacing the memory IC, be sure to use the same type IC written with the initial values of data. In other words, use the specific IC listed in "PRINTED WIRING BOARD PARTS LIST". For its mounting location, refer to "ADJUSTMENT LOCATIONS".

2. PROCEDURE FOR REPLACING MEMORY IC

(1) Power off

Switch the power off and unplug the power cord from the wall outlet.

(2) Replacing the memory IC

Replace the memory IC with new one. Be sure to use the memory IC written with the initial data values.

(3) Power on

Plug the power cord into the wall outlet and switch the power on.

(4) Check and setting of SYSTEM CONSTANT SET:

1) Press the DISPLAY key and the PICTURE MODE key on the remote control unit simultaneously. The SERVICE MENU screen will be displayed. (See Fig. 1.)

2) In the SERVICE MENU, press the DISPLAY key and PICTURE MODE key simultaneously. Then, the SYSTEM CONSTANT SET screen will be displayed. (See Fig. 2.)

3) Check whether the setting values of the SYSTEM CONSTANT SET are the same as those indicated in Table

1. If the value is different, select the setting item with the MENU a key, and set the correct value with the MENU − / + key.

4) Press the DISPLAY key twice to return to the normal screen.

(5) Receive channel setting

Refer to the OPERATING INSTRUCTIONS and set the receive channels (channels preset).

NAME OF REMOTE CONTROL KEYS

DISPLAY

MENU –

ECO

SENSOR

SYSTEM

COLOUR SOUND

TV/VIDEO

I / II

OFF

TIMER

CHANNEL

RETURN+

SCAN

DISPLAY

CHANNEL

POWER

PICTURE

MODE

456

−

VOLUME

-/- -

MUTING

+−

PICTURE MODE

MENU +

(6) User setting

Check the user setting values in Table 2, and if setting value is different, set the correct value. For setting, refer to the OPERATING INSTRUCTIONS.

(7) Setting of SERVICE MENU

Verify the setting for each setting item in the SERVICE MENU. (See Table 3.) If readjustment is necessary, perform adjustment referring to "SERVICE ADJUSTMENTS".

SERVICE MENU

1. IF

3. DEF

5. PRESET

6. TURBO TIMER OFF

1-6 : SELECT DISP : EXIT

✽✽✽✽✽✽✽✽ ✽✽✽✽✽

2. V/C

4. VSM PRESET

✽✽.✽✽✽✽

✽✽✽ ✽✽✽✽✽

✽✽.✽✽✽✽

Fig. 1

SYSTEM CONSTANT - I

SYSTEM CONSTANT SET 1/3

COLOUR : TRIPLE BILINGUAL : NO TUNER : MU ECO SENSOR : YES LANGUAGE : E / R / C

a: SELECT

− / + : OPERATE

DISP : EXIT

SYSTEM CONSTANT - II

SYSTEM CONSTANT SET 2/3

B/B SOUND : OFF LOCK : 180 COLOUR AUTO : NO QSS : MINT ALC : NO TEXT RATE : 20

a: SELECT

− / + : OPERATE

DISP : EXIT

SYSTEM CONSTANT - III

SYSTEM CONSTANT SET 3/3

AMP TUNER : NO

a: SELECT

− / + : OPERATE

DISP : EXIT

Fig. 2

No. 560136

SETTING OF SYSTEM CONSTANT SET

Table 1

Setting item Setting contents Setting value

AV-21AT

COLOUR TRIPLE BILINGUAL NO TUNER MU ECO SENSOR YES LANGUAGE E/R/C B/B SOUND OFF

LOCK 180

COLOUR AUTO NO QSS MINT ALC NO TEXT RATE 20 AMP TUNER NO

USER SETTING VALUES

MULTI. TRIPLE PAL YES NO MU MA YES NO E/R/C/U E/R/C E/R/U E/C ON OFF

YES 10 20 ... 230

250 240 YES NO MINT MQSS YES NO

10 20 40 80

YES NO

Table 2

Setting item Setting value Setting item Setting value

SUB POWER ON PICTURE MODE (VSM) BRIGHT CHANNEL POSITION 1 POSITION VNR OFF

CHANNEL PRESET

VOLUME Appropriate sound volume AUTO SHUTOFF OFF TV/VIDEO TV ECO SENSOR OFF ON SCREEN DISPLAY POSITION NUMBER DISPLAY BLUE BACK OFF COLOUR SYSTEM AUTO PAL ON TIMER PR1 0:00 SOUND SYSTEM B / G CHILD LOCK OFF

Refer to OPERATING INSTRUCTION

OFF TIMER OFF LANGUAGE ENGLISH

No. 56013 7

A V-21AT

SERVICE MENU SETTING ITEMS

Table 3

Service menu Setting item

1. IF 1. VCO

2. DELAY POINT

2. V / C 1. CUTOFF(R/G/B)

2. DRIVE(R/B)

3. BRIGHT

4. CONT.

5. COLOUR (P / S/ N3 / N4)

6. TINT (N3 / N4)

7. SECAM BL ADJ

8. SHARP (TV / VIDEO)

3. DEF 1. VER. POSITION

2. HOR. POSITION

3. VER. HEIGHT

4. VER. LINEARITY

5. VER. SCURVE

6. HOR. VCO ADJUST

4. VSM PRESET TINT (BRIGHT/STD/SOFT) COLOUR

BRIGHT CONT. SHARP

Do not adjust.

Service menu Setting item

5. PRESET 1. C-TRAP FIX

2. SHARP PEAK

3. ABL

4. GAMMA

5. Y.DELAY TIME

6. BLACK EXP START

7. C-BPF

8. CW/SCP

9. V.IF DET. LEVEL

10. S.IF DET. LEVEL

11. IF AGC MIN.

12. V.IF AGC

13. V.IF PMOD

14. S.IF BPF BW ADJUST

15. S.IF TRAP FO ADJUST

16. S.IF TRAP FO ADJUST 2

17. S.IF-TRAP

18. S.IF-BPF

19. VNR

20. RGB LIM.

21. RGB LIMIT LEVEL

22. S.IF SW

23. TEXT H. POSITION

24. READ DATA

6. TURBO TIMER ON/OFF Should be set to OFF. (When you turn the TV power off, the Turbo Timer is automatically set to OFF.)

Do not adjust.

No. 560138

REPLACEMENT OF CHIP COMPONENT

■ CAUTIONS

1. Avoid heating for more than 3 seconds.

2. Do not rub the electrodes and the resist parts of the pattern.

3. When removing a chip part, melt the solder adequately.

4. Do not reuse a chip part after removing it.

■ SOLDERING IRON

1. Use a high insulation soldering iron with a thin pointed end of it.

2. A 30W soldering iron is recommended for easily removing parts.

■ REPLACEMENT STEPS

1. How to remove Chip parts

● Resistors, capacitors, etc.

(1) As shown in the figure, while pushing the chip part with twee-

zers, alternately melt the solder at its each end.

AV-21AT

2. How to install Chip parts

● Resistors, capacitors, etc.

(1) Apply solder to the pattern as indicated in the figure.

(2) Shift the chip part with tweezers and remove it.

● Transistors, diodes, variable resistors, etc.

(1) Apply extra solder to each lead.

SOLDER

(2) As shown in the figure, while pushing the chip part with twee-

zers, alternately melt the solder at its each lead. Then, shift and remove the chip part.

SOLDER

(2) Grasp the chip part with tweezers and place it on the solder.

Then heat and melt the solder at both ends of the chip part.

● Transistors, diodes, variable resistors, etc.

(1) Apply solder to the pattern as indicated in the figure. (2) Grasp the chip part with tweezers and place it on the solder. (3) First solder lead A as indicated in the figure.

(4) Then solder leads B and C.

Note : After removing the part, remove remaining solder from

the pattern.

No. 56013 9

A V-21AT

SERVICE ADJUSTMENTS

BEFORE STARTING SERVICE ADJUSTMENT

1. There are 2 ways for adjusting this TV: One is with the REMOTE CONTROL UNIT and the other is the conventional method using adjustment parts and components.

2. The setting (adjustment) using the REMOTE CONTROL UNIT is made on the basis of the initial setting values. The setting values which adjust the screen to the optimum condition can be different from the initial setting values.

3. Make sure that connection is correctly made to AC power source.

4. Turn on the power of the TV and measuring instrument for warming up for at least 30 minutes before starting adjustment.

5. If the receive or input signal is not specified, use the most appropriate signal for adjustment.

6. Never touch parts (such as variable resistors, transformers and capacitors) not shown in the adjustment items of this service adjustment.

7. Preparation for adjustment (presetting): Unless otherwise specified in the adjustment items, preset the following functions with the remote control unit.

PICTURE MODE (VSM) COLOUR/BRIGHT/CONT./SHARP

VNR OFF TIMER ECO SENSOR BLUE BACK

Function

Setting value

BRIGHT See "VSM Preset" on page 22.

OFF OFF OFF OFF

MEASURING INSTRUMENT AND FIXTURES

1. DC voltmeter (or Digital voltmeter)

2. Oscilloscope

3. Signal generator (Pattern generator) [PAL / SECAM / NTSC]

4. Remote control unit

ADJUSTMENT/CHECK ITEMS

Adjustment/Check item Page

B1 POWER SUPPLY Check 14 FOCUS Adjustment 14 IF CIRCUIT Adjustment 14 V/C (VIDEO/CHROMA) CIRCUIT Adjustment 15 DEFLECTION CIRCUIT Adjustment 20 VSM PRESET Adjustment 22 PRESET Adjustment 23 PURITY, CONVERGENCE Adjustment 24

BASIC OPERATION IN SERVICE MENU

1. TOOL OF SERVICE MENU OPERATION

Operate the SERVICE MENU with the remote control unit.

2. SERVICE MENU ITEMS

With the SERVICE MENU, various settings (adjustments) can be made, and they are broadly classified in the following items of settings:

● 1. IF ............................. For entering/adjusting the setting values (adjustment values) of the IF circuit.

● 2. V/C........................... For entering/adjusting the setting values (adjustment values) of the VIDEO/CHROMA circuit.

● 3. DEF ......................... For entering/adjusting the setting values (adjustment values) of the DEFLECTION circuit.

● 4. VSM PRESET ......... For setting the values of STANDARD, SOFT and BRIGHT. (Do not adjust the preset values.)

● 5. PRESET .................. For setting the values for VIDEO/CHROMA control. (Do not adjust the preset values.)

● 6. TURBO TIMER........ For quick setting the values of TIMER COUNT — adjustable not only by minutes but also by second. If it is ON,

(VSM: video status memory)

the time in TIMER mode changes from 1 minute into 1 second temporarily. (Applicable to OFF TIMER, ON TIMER and AUTO SHUTOFF)

Note: When you turn the TV power off, the Turbo Timer is automatically set to OFF.

No. 5601310

AV-21AT

3. BASIC OPERATION IN SERVICE MENU

SERVICE MENU

(1) How to enter SERVICE MENU

Press the DISPLAY key and the PICTURE MODE key on the remote control unit simultaneously. The SERVICE MENU screen will be displayed. (See Fig. 1.)

SERVICE MENU

1. IF

3. DEF

5. PRESET

6. TURBO TIMER OFF

1-6 : SELECT DISP : EXIT

✽✽✽✽✽✽✽✽ ✽✽✽✽✽

2. V/C

4. VSM PRESET

✽✽.✽✽✽✽

✽✽✽ ✽✽✽✽✽

✽✽.✽✽✽✽

Fig. 1

(2) Selection of SUB MENU SCREEN

Press one of the keys 1 ~ 6 on the remote control unit, and select the SUB MENU SCREEN from the SERVICE MENU. (See Fig. 2 on the next page.)

SERVICE MENU → SUB MENU 1. IF

2. V / C

3. DEF

4. VSM PRESET

5. PRESET

6. TURBO TIMER

(3) Method of Setting

*Once the setting values are set, they are memorized automatically. *It must not adjust without inputting a signal.

1) 1. IF

[1. VCO]

(a) 1 Key ......................................... Select 1. IF.

(b) 1 Key ......................................... Select 1. VCO. (CW)

(c) VCO(CW) . ................................ Adjust VCO(CW) while watching the colour (yellow/blue) of the characters on the screen.

For details, refer to the adjustment table.

(d) DISPLAY Key ............................ When this is pressed twice, you will return to the SERVICE MENU.

[2. DELAY POINT]

(a) 1 Key ......................................... Select 1. IF.

(b) 2 Key ......................................... Select 2. DELAY POINT.

(d) DISPLAY Key ............................ When this is pressed twice, you will return to the SERVICE MENU.

2) 2. V/C, 3. DEF, 4. VSM PRESET and 5. PRESET

Note: Do not adjust "4. VSM PRESET" and "5. PRESET" unless you had changed its value by mistake.

(a) 2 ~ 5 Keys ................................. Select one from 2. V/C, 3. DEF, 4. VSM PRESET and 5. PRESET.

(b) MENU a key........................ Select setting items.

● Use the number keys on the remote control unit for setting of WHITE BALANCE and BLACK OFFSET. For the setting, refer to each item concerned.

(d) DISPLAY Key ............................ When this is pressed, you will return to the SERVICE MENU.

3) 6. TURBO TIMER

(a) 6 Key ......................................... Each time you press the key, ON/OFF state of TURBO TIMER changes.

(Should be set to OFF.)

(4) Release of SERVICE MENU

After completing the setting, return to the SERVICE MENU by pressing the DISPLAY key, then again press the DISPLAY key to return to the normal screen.

No. 56013 11

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