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AV-21YT15
Service Manual
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User Manual
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JVC AV-21YT15 Service Manual

SERVICE MANUAL
FLAT COLOR TELEVISION
YA26620057

AV-21YT15/Z, AV-21VT35/Z

BASIC CHASSIS
CW
[AV-21VT35/Z][AV-21YT15/Z]

TABLE OF CONTENTS

2 SPECIFIC SERVICE INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
3 DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
4 ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
5 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-30
COPYRIGHT © 2005 Victor Company of Japan, Limited
No.YA266
2005/7
SPECIFICATION
Items
Dimensions (W × H × D) 64.9cm × 47.05cm × 47.75cm 64.9cm × 47.8cm × 47.35cm
Mass 21kg 25kg
TV RF System M / N
Color System TV Mode
Video Mode
Stereo System MTS (Multi-Channel Television Sound)
Receiving Frequency VHF Low
VHF High
Intermediate Frequency
Color Sub Carrier Frequency 3.58MHz/4.43MHz (PAL), 3.58MHz (NTSC)
Aerial Input Terminal 75Ω unbalanced, coaxial
Power Input AC110V-AC240V, 50Hz / 60Hz (Operating Voltage 90V~260V)
Power Consumption 91W (Max.) / 65W (Avg.) 143W (Max.) / 91W (Avg.)
Picture Tube 21-inch, aspect ratio 4:3, flat square face type, tinted
Screen Size Visible size :51.0cm (Diagonal) / 41.6cm × 31.5cm (H × V)
High Voltage 26.5kV ± 1.5kV (at zero beam current) 29kV ± 1.5kV (at zero beam current)
Speaker 6.0cm × 12cm, Oval type × 26.5cm × 13cm, oval type × 2
Audio Output 3W + 3W 7W + 7W + 13W
Video / Audio Input [1/2/3]
Video / Audio Output Video
Headphone 3.5mm stereo mini jack × 1
Remote Control Unit RM-C1288-1H
S-Video [1]
Video [1/3] 1V(p-p), negative sync, 75Ω, RCA pin jack × 2
Video [2] --- 1V(p-p), negative sync, 75Ω, RCA pin jack × 1
Audio [1/3] 500mV(rms) (-4dBs ), high impedance, RCA pin jack × 4
Audio [2]
Component
Video [2] ---
NTSC3.58 PAL / NTSC3.58 / NTSC4.43
55.25 MHz ~ 127.25 MHz (CH.2 ~ CH.B)
133.25 MHz ~ 361.25 MHz (CH.C ~ CH.W+11)
UHF
367.25 MHz ~ 801.25 MHz (CH.W+12 ~ CH.69)
VIF 38.0MHz
SIF 33.5MHz (4.5MHz)
1V(p-p), 75Ω, RCA pin jack × 1
Audio
500mV(rms)(-4dBs), Low impedance (400Hz when modulated 100%), RCA pin jack × 2
(AA/R06/UM-3 battery × 2)
AV-21YT15/Z AV-21VT35/Z
---
---
Contents
13cm, round type × 1 (Bass blaster unit)
Mini-DIN 4 pin × 1 Y: 1V(p-p), positive (negative sync provided), 75Ω C: 0.286V(p-p) (Burst signal), 75Ω
500mV(rms) (-4dBs ), high impedance,
RCA pin jack × 2 RCA pin jack × 3
Y:1V(p-p), positive (negative sync), 75Ω Cb/Cr:0.7V(p-p), 75Ω
Design & specifications are subject to change without notice.
1-2 (No.YA266)
SECTION 1
PRECAUTION

1.1 SAFETY PRECAUTIONS

(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 the LIVE side GND and ISOLATED (NEUTRAL) side GND or EARTH side GND at the same time with a measuring apparatus (oscilloscope etc.). 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 B1 POWER SUPPLY check).
(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 X-Ray 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.
(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.
(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.
a) 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.
b) 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 1000Ω 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.).
AC VOLTMETER (HAVING 1000 /V, OR MORE SENSITIVITY)
0.15 F AC-TYPE
PLACE THIS PROBE
1500 10W
GOOD EARTH GROUND
ON EACH EXPOSED ME TAL PAR T
(No.YA266)1-3
SECTION 2
SPECIFIC SERVICE INSTRUCTIONS

2.1 FEATURES

• New chassis design enables use of an interactive on-screen control.
• Pure flat CRT produces fine textured picture in every detail.
• Wide range voltage (110V ~ 240V) for AC power input.
• With AUDIO/VIDEO/S-VIDEO/COMPONENT input terminals.
2
C bus control utilizes single chip ICs.
•I
• By means of AUTO PROGRAM, the TV stations can be selected automatically and the TV channels can also be rearranged automatically.
• Built-in DIGITAL 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 OFF TIMER & RETURN +.

2.2 MAIN DIFFERENCE LIST

Items AV-21YT15/Z AV-21VT35/Z
BASS BLASTER None BASS BLASTER UNIT
AUDIO OUTPUT 3W + 3W 7W + 7W + 13W
POWER CONSUMPTION 91W (Max.) / 65W (Avg.) 143W (Max.) / 91W (Avg.)
1-4 (No.YA266)

2.3 MAIN CPU [MAIN PWB : IC701] PIN FUNCTION

Pin no. Pin name I/O Remark
1VssP2 -GND
2 VssC4 - GND
3 V1.8C4 I 1.8V (Digital)
4 V3.3A3 I 3.3V
5 VrefP_Sdac I 3.3V (Positive)
6 VrefN_Sdac - GND
7 VrefP_Sdac I 3.3V (Negative)
8 VrefN_Sdac - GND
9 VrefP_Sdac I 3.3V (Positive)
10 XtalIn I 24.567MHz for system clock
11 XtalOut O 24.567MHz for system clock
12 VssA1 - GND
13 NECK I V-guard input/ I/O switch
14 CONT I 1.8V regulator control
15 V5P1 I +5V
16 Ph2 - Phase-2 filter
17 Ph1 - Phase-1 filter
18 Gnd1 - GND
19 SecPll - SECAM PLL decoupling
20 Dec8G - Bandgap decoupling
21 EW O East-West drive output
22 VDRB- O Vertical drive B output
23 VDRA+ O Vertical drive A output
24 Vif1 I Video IF input 1
25 Vif2 I Video IF input 2
26 Vsc - Vertical sawtooth capacitor
27 Iref I Reference current input
28 GndIF - GND
29 Sif1 I Sound IF input 1
30 Sif2 I Sound IF input 2
31 AGC O Tuner AGC output
32 EHT I EHT/overvoltage protection input
33 Ssif/RefIn/Avl/RefOut O
34 L3 I Audio-L3 input (left signal)
35 R3 I Audio-R3 input (right signal)
36 L_OUT O Audio L output
37 R_OUT O Audio R output
38 DecsDem - Decoupling sound demodulator
39 QssO/AmO/AudeEm O QSS intercarrier output / AM output /
40 Gnd2 - GND
41 PllIf - IF-PLL loop filter
42 SifAgc - AGC sound IF
43 IfVo/FmRo/DvbO O Not used
44 NC O Not used
45 V8AudioSwitches I 8V
46 AgcSsif - AGC capacitor second sound IF
47 V5P2 I 5V
48 V_OUT O Video output
49 L1 I Audio-L1 input
50 R1 I Audio-R1 input
51 V3 I Video V3 input
52 C4 I Not used
53 Audio2InL I Not used
54 Audio2InR I Not used
55 V2/Y I Video 2 input
56 L2 I Audio L2 input (Left signal)
57 R2 I Audio R2 input (right signal)
58 Y3/Cvbs I S-Video Y1 input
59 C1 I S-Video C1 input
60 AudioLsL O Audio L output for audio power amplifier
61 AudioLsR O Audio R output for audio power amplifier
62 HP_L O Headphone L
63 HP_R O Headphone R
Automatic Volume Levelling/ sound IF input / subcarrier reference output / external reference signal input for I signal mixer for DVB operation
deemphasis / (front-end audio out)
Pin no. Pin name I/O Remark
64 CVBSO/PIP O CVBS / PIP output
65 SVM O Scan velocity modulation output
66 FbiSo I Flyback input/sandcastle output
67 Hout O Horizontal output
68 VssComb - GND
69 V5Comb I 5V
70 Vin/R2/Pr I PIP R input
71 Uin/B2/Pb I PIP B input
72 Yin/G2/Y I PIP G input
73 Ysync I Not used
74 Yout O Not used
75 Uout/INSSW2 I YUV insertion input
76 NC O Not used
77 INSSW3 I YUV insertion input
78 R3/Pr I Component PR input (Video-2)
79 G3/Y I Component Y input (Video-2)
80 B3/Pb I Component PB input (Video-2)
81 Gnd3 - GND
82 V5P3 I 5V
83 BCL I Beam current limiter input
84 BLKIN I Black current input
85 Rout O R output
86 Gout O G output
87 Bout O B output
88 V3.3A1 I 3.3V
89 RefAdN - GND
90 V3.3RefAdP I 3.3V (Positive)
91 RefAd I 3.3/2V
92 GndA - GND
93 V1.8A I 1.8V
94 V3.3A2 I 3.3V
95 VssADC - GND
96 V1.8ADC I 1.8V
97 REMOTE I Remote control
98 PW_LED I POWER LED control
99 P11/TO I POWER LED control
100 V1.8C2 I 1.8V
101 VssC2 - GND
102 COMPONENT-PIP - Not used
103
COMB_SW_NT3.5/OTHER
104 VER_PROTECT O X-ray protect
105 S_REDUCE O Sound control
106 P00/I2SDI1 O Not used
107 POWER O SUB POWER control
108 SCL1 I I2C bus clock
109 SDA1 I/O I2C bus clock
110 V3.3P I 3.3V
111 ROTATION O ROTATION
112 3.58/OTHER O
113 A_MUTE O Audio muting
114 4.5/OTHER O NTSC 4.43 detection
115 PROT I Protect
116 ECO_IN I ECO sensor level detection
117 V1.8C1 I 1.8V (Digital)
118 DecV1V8 I 1.8V
119 KEY_IN I Key scan data
120 VDO_DET I Video DET input
121 VSSC1+P1 - Digital GND
122 P24/PWM3 I S-Video DET input
123 P25/PWM4 O GTVA_reset
124 V1.8C3 I 1.8V (Digital)
125 VssC3 - GND
126 P12/Int2 I External interrupt
127 SDA0 I/O I2C bus data (for memory)
128 SCL0 I I2C bus clock (for memory)
- Not used
NTSC 3.58 detection
(No.YA266)1-5
SECTION 3
DISASSEMBLY

3.1 DISASSEMBLY PROCEDURE [AV-21YT15/Z]

3.1.1 REMOVING THE REAR COVER
• Unplug the power cord. (1) Remove the 8 screws [A], 1 screw [B] and 2 screws [C] as
shown in Fig.1.
(2) Withdraw the REAR COVER toward you.
CAUTION:
When reinstalling the rear cover, carefully push it inward after inserting the MAIN PWB into the REAR COVER groove.
3.1.2 REMOVING THE MAIN PW BOARD
• Remove the REAR COVER. (1) Slightly raise the both sides of the MAIN PWB by hand. (2) Withdraw the MAIN PWB backward.
(If necessary, take off the wire clamp and connectors, etc.)
3.1.3 REMOVING THE SPEAKER
• Remove the REAR COVER. (1) Remove the 4 screws [D] as shown in Fig.1.
3.1.4 CHECKING THE MAIN PW BOARD
• To check the back side of the MAIN PWB. (1) Pull out the MAIN PWB. (Refer to REMOVING THE MAIN
PW BOARD).
(2) Erect the MAIN PWB vertically so that you can easily check
its back side.
CAUTIONS:
• Before turning on power, make sure that the CRT earth wire
and other connectors are properly connected.
• When repairing, connect the DEG. COIL to the DEG.
connector on the MAIN PWB.
• When repairing, connect the DEG. COIL to the DEG.
connector on the MAIN PWB.
3.1.5 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.

3.2 DISASSEMBLY PROCEDURE [AV-21VT35/Z]

3.2.1 REMOVING THE TWIN PORT BASS BLASTER UNIT
• Unplug the power supply cord. (1) Disconnect the TWIN PORT BASS BLASTER UNIT’s cord
from the rear of the TV set.
(2) Remove the TWIN PORT BASS BLASTER UNIT by pulling
it upwards.
NOTE:
After removing the TWIN PORT BASS BLASTER UNIT, proceed to the following procedure.
3.2.2 REMOVING THE REAR COVER
• Unplug the power cord. (1) Remove the 2 screws [A], 6 screws [B], 1 screw [C] and 4
screws [D] as shown in Fig.2.
(2) Withdraw the REAR COVER toward you.
CAUTION:
When reinstalling the rear cover, carefully push it inward after inserting the MAIN PWB into the REAR COVER groove.
3.2.3 REMOVING THE MAIN PW BOARD
• Remove the REAR COVER. (1) Slightly raise the both sides of the MAIN PWB by hand. (2) Withdraw the MAIN PWB backward.
(If necessary, take off the wire clamp and connectors, etc.)
3.2.4 REMOVING THE SPEAKER
• Remove the REAR COVER. (1) Remove the 2 screws [E] as shown in Fig.2. (2) Follow the same steps when removing the other hand
SPEAKER.
3.2.5 CHECKING THE MAIN PW BOARD
• To check the back side of the MAIN PWB. (1) Pull out the MAIN PWB. (Refer to REMOVING THE MAIN
PW BOARD).
(2) Erect the MAIN PWB vertically so that you can easily check
its back side.
CAUTIONS:
• Before turning on power, make sure that the CRT earth wire
and other connectors are properly connected.
• When repairing, connect the DEG. COIL to the DEG.
connector on the MAIN PWB.
• When repairing, connect the DEG. COIL to the DEG.
connector on the MAIN PWB.
1-6 (No.YA266)
3.2.6 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.
PICTURE TUBE
FRONT CABINET
D
(X4)
SPEAKER
MAIN PWB (CRT SOCKET PWB)
D
(X4)
FBT
SPEAKER
REAR COVER
MAIN PWB
A
(X8)
B
(X2)
C
Fig.1
(No.YA266)1-7
SPEAKER
PICTURE TUBE
FRONT CABINET
E
E
(X2)
SPEAKER
MAIN PWB (CRT SOCKET PWB)
FBT
(X2)
REAR COVER
MAIN PWB
(X6)
TWIN PORT BASS BLASTER UNIT
B
A
(X2)
C
1-8 (No.YA266)
D
(X4)
Fig.2

3.3 REPLACEMENT OF MEMORY IC

3.3.1 MEMORY IC
This TV uses the following memory IC.
Memory IC: IC702 on MAIN PWB
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".
3.3.2 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 [] / [] 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).
6. User setting
Check the user setting values in Table 2 and Table 3. 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 4.) If readjustment is necessary, perform adjustment referring to "ADJUSTMENTS PROCEDURE".
NAME OF REMOTE CONTROL KEYS
SERVICE MENU
SERVICE MENU
1. IF
3. AUDIO
5. VSM W/B
7. PLUG & PLAY (ON)
1-7 : SELECT DISPLAY : EXIT
******* **** ***** ***** **** **** *** ***
2. V/C
4. DEF
6. S TATUS
Fig.1
SYSTEM CONSTANT-1
SYSTEM CONSTANT
SYSTEM OTHERS COMB TILT SUPER BASS
: SEL  : OPE

SET 1
NO NO NO
DISP : EXIT
SYSTEM CONSTANT-2
SYSTEM CONSTANT SET 2
SOUND BLUE BACK MUTE ECO SENSOR
: SEL  : OPE

STEREO NO NO
DISP : EXIT
SYSTEM CONSTANT-3
SYSTEM CONSTANT SET 3
SURROUND

: SEL  : OPE
YES NOPICTURE BOOSTER NOCOMPONENT NOS INPUT
DISP : EXIT
Fig.2
DISPLAY / BACK
MENU
PICTURE MODE
MENU
MENU
MENU
(No.YA266)1-9
3.3.3 FACTORY SETTING VALUE
SETTING OF SYSTEM CONSTANT SET
Setting item Setting content
SYSTEM OTHERS
COMB NO
TILT NO
SUPER BASS YES
SOUND STEREO
BLUE BACK MUTE NO
ECO SENSOR NO
SURROUND YES
PICTURE BOOSTER NO
COMPONENT NO
S INPUT NO
TAIWAN OTHERS
YES NO
YES NO
YES NO
STEREO PB MONO
YES NO
YES NO
YES NO
YES NO
YES NO
YES NO
Setting
AV-21YT15/Z AV-21VT35/Z
NO
value
YES
YES
YES
Table 1
1-10 (No.YA266)
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