JVC AV-21U4 User manual

SERVICE MANUAL
COPYRIGHT © 2005 Victor Company of Japan, Limited No.YA252
2005/3
COLOUR TELEVISION
YA25220053
AV-21U4/SK
TABLE OF CONTENTS
1 PRECAUTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
2 SPECIFIC SERVICE INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
3 DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
4 ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12
5 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25
BASIC CHASSIS
CW

1-2 (No.YA252)
SPECIFICATION
Design & specifications are subject to change without notice.
Items Contents
Dimensions (W ×H ×D) 50.3cm ×46.7cm ×48.0cm
Mass 20kg
TV RF System B, G, I, D, K
Colour System TV Mode
Video Mode
PAL / SECAM
PAL / SECAM / NTSC3.58 / NTSC4.43
Receiving Frequency VHF Low
VHF High
UHF
CATV
46.25MHz ~ 140.25MHz (AS0 ~ S6)
147.25MHz ~ 423.25MHz (S7 ~ S36)
431.25MHz ~ 863.25MHz (S37 ~ C57)
Mid : X ~ Z, S1 ~ S10
Super: S11 ~ S20
Hyper: S21 ~ S41
Intermediate
Frequency
VIF 38.0MHz
SIF D/K: 31.5MHz (6.5MHz)
I: 32.0MHz (6.0MHz)
B/G: 32.5MHz (5.5MHz)
Colour Sub Carrier Frequency 4.43MHz (PAL), 4.40MHz/4.25MHz (SECAM), 3.58MHz/4.43MHz (NTSC)
Aerial Input Terminal 75Ωunbalanced, coaxial
Power Input AC110V ~ AC240V, 50Hz / 60Hz
Power Consumption 81W (Max.) / 57W (Avg.)
Picture Tube A51KQK99X01
21-inch, aspect ratio 4:3, convetional square face type, tinted
Screen Size Visible size : 50.5cm (Diagonal) / 40.4cm ×30.3cm (H ×V)
High Voltage 26.5kV±1.5kV (at zero beam current)
Speaker 5cm ×9cm, Oval type ×2
Audio Output 3W
Video / Audio Input
[1/2]
Video [1/2]
Audio [1/2]
1V(p-p), negative sync, 75Ω, RCA pin jack ×2
500mV(rms) (-4dBs ), high impedance, RCA pin jack ×2
Video / Audio Output Video
Audio
1V(p-p), 75Ω, RCA pin jack ×1
500mV(rms)(-4dBs), Low impedance (400Hz when modulated 100%), RCA pin jack ×1
Headphone 3.5mm stereo mini jack ×1
Remote Control Unit RM-C1261-2H
(AA/R06/UM-3 battery ×2)

(No.YA252)1-3
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 1000Ωper 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)
PLACE THIS PROBE
ON EACH EXPOSED
METAL PART
1500 10W
0.15 F AC-TYPE
GOOD EARTH GROUND

1-4 (No.YA252)
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 input terminals.
•I
2C bus control utilizes single chip ICs.
• By means of AUTO PROGRAM, the TV stations can be selected automatically and the TV channels can also be rearranged
automatically.
• Built-in OFF TIMER & RETURN +.
2.2 FUNCTIONS
REMOTE CONTROL UNIT
RM-C1261-2H
1
4
5
3
2
6
7
8
9
11
10
1
2
3
4
5
6
7
8
9
10
SOUND SYSTEM key
COLOUR SYSTEM key
FAVORITE CHANNEL
keys
DISPLAY / BACK key
PICTURE MODE key
OFF TIMER key
RETURN + key
TV / VIDEO key
Not used
PICTURE BOOSTER key
MENU ( ) key
11
12
13
14
15
CHANNEL (-/+) keys
Number keys
MENU/OK key
POWER key
17
-/--
key
MUTING key
16
MENU ( , /) keys /
VOLUME (-/+) keys
18
12
13
14
15
16
17
18

(No.YA252)1-5
2.3 MAIN CPU [MAIN PWB : IC701] PIN FUNCTION
Pin
no. Pin name I/O Function
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 24.576MHz for system clock
11 XtalOut O 24.576MHz 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 Automatic Volume Levelling/ sound IF input /
subcarrier reference output / external reference
signal input for I signal mixer for DVB operation
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 /
deemphasis / (front-end audio out)
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 V2 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
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 - Not used
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 data
110 V3.3P I 3.3V
111 ROTATION O ROTATION
112 3.58/OTHER O NTSC 3.58 detection
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)
Pin
no. Pin name I/O Function