Sharp VT-3448X User manual

I
VT-3448X
VT-51 48X
’ SHARP
SERVICE MANUAL
S77Cl VT-3448X
TV/VCR COMBINATION
TELEVIDEO
9
VT-3448X VT-51 48X
,
MODELS
VT-51 48X
i
I
In the interests of user-safety (Required by safety regulations in some countries) the set should be restored to its
original condition and only parts identical to those specified should be used.
FEATURE
n Full Auto Search Tuning System
n On Screen Digital Channel/Sound Level/Tuning
Display, Control (Contrast, Colour, Brightness, Tint, P-
Tone) Symbol and Level
n Blue Back Off Timer
n 39 Key, Wireless Remote Control Unit
n Channel Skip
n High Speed and Double Speed Video Search System
l PAL : 3 times/7 times (SP/LP)
@ NTSC : 3 times/5 times (SP/LP)
5 times/l5 times (EP)
n DPSS (Digital Program Search System)
n Quick Start Playback with Full Loading System
n Digital Automatic Tracking Control
n Automatic Playback Function
n AHC (Automatic Head Cleaning System)
n Sharp Super Picture
CONTENTS
Page
l
SPECIFICATIONS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
l
IMPORTANT SERVICE NOTES . . . . . . . . . . . ..a............ 3
l
LOCATION OF USER’S CONTROL . . . . . . . . . . . . . . . . . . . . 4
l
DISASSEMBLY AND REASSEMBLY
. . . . . . . . . . . . . . . . . . 6
l ADJUSTMENT OF THE TV ELECTRICAL
CIRCUITRY
.................. ..~....................................
9
l
PRECAUTIONS IN REASSEMBLING . . . . . . . . . . . . . . . 23
l FUNCTION OF MAJOR MECHANICAL
PARTS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24
l ADJUSTMENT, REPLACEMENTAND
Page
l TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
l CHASSIS LAYOUT
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
65
l BLOCK DIAGRAM OF TV SECTION . . . . . . . . . . . . . . . . . 67
l DESCRIPTION OF TV SECTION
SCHEMATIC DIAGRAM
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
l BLOCK DIAGRAM OF VCR SECTION
. . . . . . . . . . . . . 85
l DESCRIPTION OF VCR SECTION
SCHEMATIC DIAGRAM
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
95
l PRINTED WIRING BOARD ASSEMBLIES...... 101
l
ASSEMBLY OF MECHANICAL UNITS . . . . . . . . . . . . . . 26
REPLACEMENT PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . 107
l PACKING
l ADJUSTMENT OF THE VCR
OF THE SET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
ELECTRICAL CIRCUITRY
. . . . . . . . . . . . . . . . . . . . . . . ..a...... 44
WARNING
The chassis in this receiver is partially hot. Use an isolation transformer between the line cord plug and power
receptacle, when servicing this chassis.
To prevent electric shock, do not remove cover.
No user -
serviceable parts inside. Refer servicing to qualified service personnel.
SHARP CORPORATION

VT-3448X
VT-51 48X
SPECIFICATIONS
E OF THE PRODUCT
Power Source:
Power Consumption:
Receiving Broadcast Standard:
Receiving Channel:
Receiving System:
Antenna Input Impedance:
Video Signal:
Audio Signal:
Temperature:
Dimensions (Approx.):
Weight (Approx.):
Cabinet Material:
Accessories:
220-240 VAC, 50 Hz
VT-3448X : 77 W
VT-5148X : 98 W
B/G
VHF; 1 A-S20
UHF; s21 -c57
Sound; 5.5 MHz
Colour; PAUNTSC (AV INPUT only)
VHF/UHF; 75 ohm Unbalanced (DIN)
Input;
0.5-2.0 Vp-p/75 ohm (RCA)
output; 1 .O Vp-p/75 ohm (RCA)
Input; 0.5 Vrms/lOk ohm (RCA)
output; 0.5 Vrms/l k ohm (RCA) (54% MOD)
Operation; 5°C to 40°C
Storage;
-1OOC to 60°C
VT-3448X : 352 mm (W) x 387 mm (H) x 382 mm (D)
VT-5148X : 504 mm (W) x 505 mm (H) x 470 mm (D)
VT-3448X : 12.4 kg
VT-5148X : 23.4 kg
Plastic
0 Operation Manual
0 Infrared Remote Control Unit
c] Dry Batteries, Type AA (x2pcs)
HTV SECTION
Viewing Area:
Picture Power:
Speaker Output:
Picture Tube:
WCR SECTION
VT-3448X : 33.54 cm Diagonal Measurement
VT-5148X : 50.8 cm Diagonal Measurement
VT-3448X : 22.0 kV at 800 uA Beam Current
VT-5148X : 25.0 kV at 1100 uA Beam Current
VT-3448X : 3.0 W at Max. (8 cm Round Dynamic xlpc)
VT-5148X : 3.0 W at Max. (8 cm Round Dynamic xlpc)
Type;
VT-3448X : VB370BVBKI S-S (Tint Tube)
VT-5148X : VB51 KPD12X/4E (Tint Tube)
Heater; VT-3448X : 6.3 V, 300 mA
VT-5148X : 6.3 V, 600 mA
Focus; High Bi-Potential Electrostatic
Outline:
Format:
Video Recording System:
Luminance:
Chrominance:
Video Signal System:
Cassette Tape:
Tape Width:
Tape Speed:
Recording/Playback Time:
VHS Video System Colour Video Cassette Recorder
VHS PAUNTSC Standard
Rotary Slant Azimuth 2-Head Helical Scan System
FM Recording
Low Frequency Converted Direct Recording
PAUNTSC 3.58MHz Colour
VHS Type Video Cassette Tape
12.7 mm
PAL ;
23.39 mm/s (SP), 11.70 mm/s (LP)
NTSC ;
33.35 mm/s (SP), 16.68 mm/s (LP.PB only), 11.12 mm/s (EP)
SP ; Max. 240 min (with E-240)
LP ;
Max. 480 min (with E-240, PAL only)
EP ; Max. 480
min (with T-160, NTSC only)
Note: The antenna must correspond to the new standard DIN 45325 (IEC 169-2) for combined UHF antenna with
75 ohm connector.
Specifications are subject to change without prior notice.
2

I
VT-3448X
VT-51 48X
IMPORTANT SERVICE NOTES
Maintenance and repair of this receiver should be done by qualified service
personnel only.
SERVICING OF HIGH VOLTAGE SYSTEM AND
PICTURE TUBE
When servicing the high voltage system, remove static charge from it by
connecting a IOk ohm Resistor in series with an insulated wire (such as a
test probe) between picture tube dag and 2nd anode lead. (AC line cord should
be disconnected from AC outlet.)
1. Picture tube in this receiver employs integral implosion protection.
2. Replace with tube of the same type number for continued safety.
3. Do not lift picture tube by the neck.
4. Handle the picture tube only when wearing shatterproof goggles and after discharging
the high voltage completely.
X-RAY
This receiver is designed so that any X-Ray radiation is kept to an absolute
minimum. Since certain malfunctions or servicing may produce potentially
hazardous radiation with prolonged exposure at close range, the following
precautions should be observed:
1. VT-3448X:
When repairing the circuit, be sure not to increase the high voltage to more
than 25.3 kV, (at beam 0 PA) for the set.
VT-51 48X:
When repairing the circuit, be sure not to increase the high voltage to more
than 29.3 kV, (at beam 0 PA) for the set.
2. VT-3448X:
To keep the set in a normal operation, be sure to make it function on 22.0 kV
+ 1.5 kV - 2.0 kV (at beam 800 PA) in the case of the set. The set has been
factory - Adjusted to the above-mentioned high voltage.
VT-5148X: To keep the set in a normal operation, be sure to make it function on 25.0 kV 2
1.5 kV (at beam 1100 PA) in the case of the set. The set has been factory -
Adjusted to the above-mentioned high voltage.
* If there is a possibility that the high voltage fluctuates as a result of the repairs, never . .
forget to check for such high voltage after the work.
3. Do not substitute a picture tube with unauthorized types and/or brands which may cause
excess X-ray radiation.
BEFORE RETURNING THE RECEIVER
Before returning the receiver to the user, perform the following safety checks.
1. Inspect all lead dress to make certain that leads are not pinched or that hardware is not
lodged between the chassis and other metal parts in the receiver.
2. Inspect all protective devices such as non-metallic control knobs, insulating fishpapers,
cabinet backs, adjustment and compartment covers or shields, isolation resistor-capac-
ity networks, mechanical insulators etc.
3

VT-3448X
VT-51 48X
LOCATION OF USER’S CONTROL
STOP/EJECT button
POWER button
EO/AUDIO INPUT terminals
01 VA A VCH A S.PICTlJRE.REC
CHILD-LOCK indicator
PROGRAM TIMER Indicator
REC indicator
POWER/WAKE-UP TIMER
indicator
button SHARP SUPER PICTURE button
(This function WIII create a clearer image dunng playback.)
CHANNEL UP/DOWN buttons
VOLUME UP/DOWN buttons
I Rear1
VIDE IO
INPUT
--.I
I
? AUDIO
VIDEO
OUTPUT
ANTENNA IN terminal
INPUT
OUTPUT
This operation manual is for VT-3448X and VT-
4

LOCATION OF USER’S CONTROL (Continued)
I Remote Control I
TVA/IDE0 Select button
STANDBY/ON button
CHANNEL SELECT buttons-,
FLASHBACK button
Returns to previously
viewed channel.
COUNTER RESET button
l Used to reset the tape
counter.
TAPE SPEED button
l Used to select the recording
tape speed.
------\Y
PLAY button
l Used for tape playback.
l Used to cancel the PAUSE/
STILL mode and return to nor-
mal playback operation.
/--
REW button 2
l Used to rewind the tape or to
conduct Reverse Video Search
during playback mode.
REC button
l Used to record a programme.
CONFIRM button -
l Used to confirm the
programme setting.
Infrared Transmitter Window
DISPLAY button
l Used to change the On
Screen Dtsplay
I-MI ITF hl attnn
sound Press + Mutes
Press again + Restores
sound to previous level.
VOLUME UP/DOWN buttons
CHANNEL UP/DOWN
buttons (TRACKING ,@/@)
l Used to select the
CHANNEL.
l Used to adjust the TRACK-
ING whrle playing the tape
CHILD-PROOF LOCK button
l Used to lock any selected
mode.
FF button
l Used to fast forward the
tape or to conduct Forward
Video Search dunng play-
back mode.
STOP button
l Used to stop the tape.
PAUSE button
l Used to temporarily stop the
tape during recording mode.
l Used to display a still
picture during p!ayback
mode.
SHARP
DPSS buttons
TV-VCR COMBINATION
l Press the (s/e) button to
search for the Index signal
and begin playback auto-
matically.
RETURN button -----/
SET button /
PROGRAMME button
. Press the button to set the
programme Timer.
n Installing dry batteries in the remote control unit
I,.....- MENU button
l Used to select the menu
screen.
Before using the TV set for the first time, install the supplied dry batteries in the remote control.
Inserting batteries
0 With your thumb nail, pull up the slit as indicated by the arrow
to remove the back cover.
Pull up
@Insert two batteries (size “AA”). Be sure to match the battery
O/O terminals with the @/@ marks inside the compartment.
@Replace the battery cover.
l Remove batteries if weak or if the unit IS not in use for long periods.
l Do not mrx old and new batteries.
l Incorrect installation of the batteries may damage the remote control.
5

VT-3448X
I
VT-51 48X 1
DISASSEMBLY AND REASSEMBLY
1. Remove the 9 rear cover fixing screws and detach the rear cover.
2. Take out the anode cap, CRT PWB, connectors F and G, coating ground, SP chip, fixing screws and others.
3. Remove the 2 Main PWB fixing screws and take out the Main PWB unit and the Power PWB unit.
4. Remove the 4 Power PWB fixing screws, and take out the Power PWB unit.
VT-3448X
c--l
1
VT-51 48X

DISASSEMBLY AND REASSEMBLY (Continued)
4
5. Remove the 7VCR fixing screws, and detach the shielding case.
6. Remove the 4 cassette housing control fixing screws, and detach the cassette housing control.
7. Remove the 2 Power SW PWB fixing screws, and detach the Power SW PWB.
8. Remove the 6 mechanism chassis fixing screws, and detach the mechanism chassis from the Main PWB.
9. Remove the 4 Main PWB fixing screws, and detach the Main PWB.
0
6

DISASSEMBLY AND REASSEMBLY (Continued)
For servicing any of the components inside, disconnect the lead dressing holder. Position the main PWB unit upright
as shown below and connect the leads for starting the services.
Note: Fit the VCR unit the front cabinet with the front flap door tilted at 70-80”.

I
VT-3448X
VT-51 48X
ADJUSTMENT OF THE TV ELECTRICAL CIRCUITRY
ADJUSTMENT PRECAUTIONS
1. Calling the service mode
(1)
Place the set in the stand-by mode.
(2)
Hold down the CH UP button (CH A) of the set for 3 seconds or longer. Then press the STAND BY/ON button
(&I) of the set.
(3) Now the set will be in the service mode.
2. Getting out of the service mode
There are three ways to get out of the service mode.
(1)
Press the MENU key on the remote controller.
(2)
Bring the set into the stand-by mode.
(3) Turn off the MAIN POWER switch.
3. On-screen display in the service mode
A service mode item and its data appear in two lines
at the lower left on the screen. Top line : Service mode item (See below)
\
Bottom line : Data (See below) bW
Service mode
Item Display
Data Variable range
DIRECT MODE DIRCT * Adjustable in the DIRECT MODE
V-AMPLITUDE V-AMP 0 - 127 R CUT OFF
(0 - 255)
V-LINEARITY V-LIN 0 - 31 G CUT OFF
(0 - 255)
V-OUT PHASE v-POS o- 7 B CUT OFF (0 - 255)
H-POSITION H-POS
0 - 31
G DRIVE GAIN (0 - 255)
BELL FILTER BELL
o- 3B DRIVE GAIN
(0 - 255)
R-Y BLACK OFFSET
R-Y
o- 15
B-Y BLACK OFFSET B-Y o- 15
Y-SUB CONTRAST
CONT 0 - 31
SUB COLOUR
COLOR
0 -240
SUB BRIGHT BRI
0 -150
SUB TINT TINT 0
- 37
Note :
Item selectable by the CH Av keys and data by the VOL Irv keys (effective on both the
remote controller and the set)
The numeric keys on the remote controller work as follows in the DIRECT mode only.
R CUT OFF
G CUT OFF
B CUT OFF
G DRIVE GAIN
B DRIVE GAIN
UP
DOWN
1 4
2
5
3
6
7
5
8 0
Notes :
In all the other modes, these keys are used to select channels.
In the DIRECT TUNING mode, these keys are used to enter data.
9

VT-3448X
VT-51 48X I
Item-by-item control in the service mode
1. DIRECT mode
F-B/W
o->I (forced B/W)
2. DIRECT mode + HOR. POS. mode
DRV CNT 0->I (drive forced center)
SUB-BRIGHT Initial value
R.G.B. CUTOFF 0
(E2PROM data resumed when any of the “1” thru
“6” keys on the remote controller is pressed)
3. R-Y Black Offset
4. B-Y Black Offset
CONTRAST MAX (USER-CONTROL)
BRIGHT MAX (USER-CONTROL)
COLOUR CENTER (USER-CONTROL)
R-MONITOR SW 0 - > 1 (MONITOR OUT)
MUTE MODE
Y-MUTE
CONTRAST MAX (USER-CONTROL)
BRIGHT MAX (USER-CONTROL)
COLOUR CENTER (USER-CONTROL)
B-MONITOR SW 0 - > 1 (MONITOR OUT)
MUTE MODE Y-MUTE
5. SUB Tint MUTE MODE
Y-MUTE
6. Unspecified items PICTURE NORMAL (CONT. BRI. COL.)
Note :
All the settings will be back to the initial ones when shifting into any other mode or getting out of the
service mode.
Allocation of special keys in the service mode
*HORIZONTAL POSITION key CONFIRM (SET
-> S-PICTURE)
*Y-MUTE KEY SET
*COLOUR MAXIMIN. select key TIMER ON/OFF
*DIRECT TUNING MODE KEY
RETURN
*VCR SLOW TEST KEY
PROG
*NVM MODE KEY DISPLAY
Adjustment precautions
1) Basically follow the sequential order of adjustments.
(Unless otherwise specified, follow the adjustment procedures.)
2) The “*“-marked steps in the adjustment procedures are automatically taken when in the service mode. Leave
out these steps.
3) For adjustments in the service mode, it is necessary to have the remote controller at hand.
Trouble indicators
If the set is interrupted by the protectors, the following indicators work to identify a spot in trouble.
’
1) &I LED (red) flashing : Deflection system protector activated
2) REC LED flashing (high-voltage or beam protector)
: IIC bus line error
3) LED off
(VCJ or tuner, EEPROM)
: Power protector activated
(+B line short-circuited)

VT-3448X
VT-51 48X
Initial settings of EEPROM data
Initial settings of adjustment items
Item
Variable range Initial setting
R CUT OFF 0 - 255 0
G CUT OFF 0 - 255 0
B CUT OFF 0 - 255 0
V-AMPLITUDE 50Hz 0 - 127 58
V-AMPLITUDE 60Hz 0 - 127 60
V-LINEARITY 50Hz 0 - 31 23
V-LINEARITY 60Hz 0 - 31 17
V-OUT PHASE 50Hz 0 - 704
V-OUT PHASE 60Hz 0 - 7 01
HORIZONTAL POSITION 50Hz 0 - 31 08
HORIZONTAL POSITION 60HZ 0 - 31 12
Y-SUB CONTRAST 0 - 31 10
SUB-COLOUR 0 - 240 87
SUB-BRIGHT 0 - 150 76
G-DRIVE GAIN 0 - 255 132
B-DRIVE GAIN 0 - 255 94
SUB-TINT 0 - 37 16
BELL FO 0 - 3 01
R-Y BLACK OFFSET 0 - 15 12
B-Y BLACK OFFSET 0 - 15 11
PICTURE Adjust User setting
Initial setting : NORMAL (CONTRAST at MAX, others at CENTER)
11

VT-3448X
VT-5 148X
SERVICE ADJUSTMENT
n PIF/AFT/AGC ADJUSTMENT
1. TUNER IFT : TU201 (preset)
1. Get the tuner ready to receive the E-9CH signal,
but with no signal input. Adjust the PLL data.
2. Connect the sweep generator’s output cable to
the tuner antenna. (RF sweep)
3. Adjust the sweep generator’s output level to 80
dBpV.
4. Connect the response lead (use a low-impedance
probe with wave detector; see Fig.7) to the tun-
er’s IF output terminal.
I F-OUT
1 OOOp
1OkQ
~‘~‘~‘~~oscope
(This terminal must have the probe alone con-
nected.)
Fig. 7
5. Set the RF AGC voltage to OV - 6V with no con-
tact with the waveform.
6. Adjust the tuner IF coil to obtain the waveform as
shown in Fig. 2.
E-9CH
Note : Be sure to keep the tuner cover in posi-
tion during this adjustment.
2. VCO and AFT ADJUSTMENT : T203 (VCO), T204 (AFT)
1. VCO coil (T203)
1) Disconnect the antenna from the tuner antenna
terminal.
2) Apply DC voltage to pin (4) (IF AGC, TP202)
of IC201.
l DC voltage: 6.0 +O.l V
Fig. 2
3) Using a digital voltmeter, measure the DC volt-
age at pin (20) (PLL FIL, TP203) of IC201.
l (The digital voltmeter must be able to take
readings down to the third decimal place.)
10 kHz at 0.007 V
4) Relieve TP202 of the DC voltage.
5) Reconnect the antenna in position and receive
the E-12CH signal.
l (With the AFT off, adjust the receiving fre-
quency to 224.25 MHz.)
DC voltage at TP201
6V
3.3v
------
6) Connect the DC digital voltmeter to TP203.
Adjust T203 so that the voltmeter should read
the same voltage as in Step 3).
l Allowable error: 0.015 V (20 kHz)
2. AFT coil (T204)
1) Receive the E-l 2CH signal in the same condi-
tion as in Step 5) above.
DOWN A B’ B B”
c UP
Fig. 3
2) Connect the oscilloscope to pin 1 (AFT, TP201)
of IC201.
3) Adjust T204 so that the DC voltage reading be
3.3 v.
l 3.3 +O.l V (from the O-6.6 V variable range)
12

VT-3448X
VT-51 48X
H PIF/AFT/AGC ADJUSTMENT(Continued)
3. RF AGC CUT-IN ADJUSTMENT : R216
1. Receive the “E-12CH” (PAL COLOUR BAR) sig- Oscilloscope
TV Set
nal.
l Field strength: 57 +I dBpV (75 ohms open)
2. Connect the oscilloscope to TP204, as shown at
right.
3. Turn R216 to have the highest voltage.
4. Turn R216 slowly in the opposite direction until
the voltage goes down 0.1 V below the highest
level.
5. Adjust the signal level to 63 - 67 dBpV and make
sure there is no noise.
6. Now adjust the signal level to 90 - 95 dB@/ and
make sure there is no chrominance modulation
beat.
Note : If a 50-ohm field strength meter is used
without a 50/75 impedance converter, set
the field strength to 55 +I dBpV. Pay atten-
tion to a loss that would be caused with
the converter.
J
Bias box
Fig. 4
Bias box:About 6.5V
13

W--3448X
VT-5 148X
m PURITY ADJUSTMENT
1. PURITY ADJUSTMENT
1.
First of all, let a beam current of over 400pA flow
in the set to warm it up for 30 minutes or longer.
(over 700 PA for VT-5148X).
2.
Keep the purity magnet in the zero magnetic field
in advance. Roughly adjust the static conver-
gence.
3. Receive the green-only colour signal. Adjust the
beam current to about 500 PA. (about 770 PA for
VT-5 148X)
4. Degauss the cathode ray tube enough with the
degaussing coil.
ADJUSTMENT
Eastward magnetic field specified
1) Observe the beam landings “a” and “b”, as
shown in Fig. A, through a microscope. Ad-
just the landings as specified.
2) If the right and left landings are equally out-
ward as shown in Fig. B, move the deflection
yoke forward.
3) If the right or left landing is shifted to the right
or to the left, as shown in Fig. C and Fig. D,
adjust the opening angle of the purity magnet.
4) Make sure the right and left beam landings are
just as specified about the screen center. Now
check the cathode ray tube corners.
Be sure that all the landings are at rank “B”.
5) If any other colour appears on the screen,
move the deflection yoke back and forth.
LANDING ERROR
l Outward: Move the deflection yoke forward.
l Inward: Move the deflection yoke backward.
6) Receive the monoscope pattern signal.
RASTER ROTATION
7) Adjust the raster rotation to “0” eastward.
l Adjustment error : 0 +2 mm
8) Tighten up the deflection coil screws.
l Tightening torque : II+2 kg
Note : Each time the single-colour key is pressed,
the screen colour changes as follows.
/
3
a
b
--j
-- ----
I
Left
,
I’
~II
\
\
Left
Fig. A
Right
Beam landing equally outwards
Fig. B
.\
:I’
6’
m
Left
landing shifted to right.
Fig. C
Right
\\
li
/’
Right
Beam landing shifted to the left.
Fig. D
14

VT-3448X
VT-51 48X
H CONVERGENCE ADJUSTMENT
LCONVERGENCE ADJUSTMENT
(to be done after the purity adjustment)
BGR
1. Receive the crosshatch pattern signal.
2. Using the remote controller, call the Normal mode.
STATIC CONVERGENCE
1. Turn the 4-pole magnet to a proper opening an-
gle in order to superimpose the blue and red col-
ours.
2. Turn the 6-pole magnet to a proper opening an-
gle in order to superimpose the green colour over
the blue and red colours.
DYNAMIC CONVERGENCE
1. Adjust the convergence on the fringes of the
screen in the following steps.
l Fig. a : Drive the wedge at point “a” and
I ‘,
Fig. a
RGB
_________________ 4 ____ i
I
L- ’
----.------ --1.
’ I
swing the deflection coil upward.
l Fig. b : Drive the wedges at points “b” and
“c” and swing the deflection coil
downward.
l Fig. c : Drive the “c” wedge deeper and
swing the deflection coil rightward.
l Fig. d :Drive the ‘Id” wedge deeper and
swing the deflection coil leftward.
2. Fix all the wedges on the cathode ray tube and
apply glass tape over them.
3. Apply lacquer to the deflection yoke lock screw,
magnet unit (purity, 4-pole and 6-pole magnets),
and magnet unit lock screw.
Finally receive the red-only and blue-only colour sig-
nals and make sure there is no other colour mixed
on the screen.
RGB
\
\ :
\ :
\ :
--__ --a_
1:
----
-- R
_H--
,--- -~ --___
G
‘\
--__
:\
--. B
’ \
1’ \
1’ \
Fig. b
BGR
I
--------I-
I
I
--------- - ------- 4-.
III
II
IIII
I
Wedge “a”
Fig. d
Fig. 5
15

n CRT CUT-OFF, BACKGROUND AND SUB-CONTRAST ADJUSTMENT (1)
1 .CRT CUT-OFF (l*C bus data adjustment)
1. Receive the monoscope pattern signal.
2. Put the set in the service mode and call up the DIRECT mode (DIRCT).
3. Set the screen control to O/IO position.
4. Press the “CONFIRM” key on the remote controller to reach the horizontal centering mode. (S-PICTURE key on
the set)
5. Turn the screen control clockwise until the horizontal raster of the first glimmering colour becomes slightly
visible.
6. Adjust the cut-off data of the other two colours until the horizontal raster becomes whitish.
Note : The data can be turned up and down with the above keys.
l R CUT OFF UP
“1 ” KEY l G CUT OFF DOWN “5” KEY
l R CUT OFF DOWN “4” KEY l B CUT OFF UP
“3” KEY
l G CUT OFF UP
“2” KEY l B CUT OFF DOWN “6” KEY
7. Turn the screen control counterclockwise until the horizontal raster disappears.
Note : Before starting this adjustment, warm up the unit for 30 minutes or longer at a beam current of over
600 PA (over 700 yA for VT-5148X).
8. Press the “CONFIRM” key on the remote controller to call up the NORMAL mode. (S-PICTURE key on the set)
SUB-BRIGHTNESS (l*C bus data adjustment)
9. Using the remote controller, call the SUB-BRIGHT setting mode (BRI). (Receive the crosshatch and gray scale
signal.)
lO.Set the sub-brightness data so that the third black portion (1st to 5th counted from the left of the screen) of the
window pattern looks sinking.
Note : The service mode adjustment in the above steps (9) and (10) should be carried out after the white
balance and background adjustments.
11. Exit from the service mode.
2. WHITE BALANCE AND BACKGROUND (l*C bus data adjustment)
1. Receive the (monoscope pattern) signal.
2. Put the set in the service mode and call up the DIRECT mode (DIRCT).
3. Connect the beam ammeter between TP601 and TP602.
4. Using the sub-contrast control, roughly adjust the beam current to about 700 uA (about 1,000 uA for VT-51 48X).
5. Adjust the G-drive and B-drive data to have a colour temperature of 12,300”K (white).
l 12,300”K x : 0.272
y : 0.275
(with a Minolta colour temperature meter CA-1 00)
Note : The data can be turned up and down with the above keys.
l G-DRIVE UP
“7” KEY l B-DRIVE UP
“8” KEY
l G-DRIVE DOWN “5” KEY l B-DRIVE DOWN
“0” KEY
6. Adjust the contrast and brightness controls to have the beam current of 200 uA or so. Now check the back-
ground colour. If the colour temperature is not as specified, go back to No, 1 on the preceding page.
7. Exit from the service mode.
Note : Before starting this adjustment, warm up the unit for 30 minutes or longer at a beam current of over
600 PA (over 700 PA for VT-5148X).
16

n CRT CUT-OFF, BACKGROUND AND SUB-CONTRAST ADJUSTMENT (2)
3. SUB-CONTRAST
(l*C bus data adjustment)
1, Receive the crosshatch pattern signal.
2. Put the set in the service mode and select the SUB-CONTRAST mode (CONT).
3. Adjust the sub-contrast data to “0” (VT-3448X)/ “10” (VT-51 48X).
4. Exit from the service mode.
n HORIZONTAL AND VERTICAL CIRCUIT ADJUSTMENT
1. SERVICE MODE DATA ADJUSTMENT
Put the set in the service mode.
Turn up or down the data for this adjustment.
l V-AMP 50 Hz
A) Select the V-AMP mode (V-AMP). Adjust the
overscan to 10% .
l V-LINEARITY - 50 Hz
9) Select the V-LIN mode (V-LIN). Adjust to get the
Note :
The selected channels in parentheses have the
following signals.
best linearity.
l V-OUT PHASE - 50 Hz (V-CENTER)
C) Select the V-OUT POS mode (V-POS). Align the
screen center with the cathode ray tube’s geo-
metrical center.
l H-POS 50 Hz (H-CENTER)
D) Select the H-POS mode (H-POS). Make the dis-
tances “A” and “9” on both sides equal.
l*C bus data adjustment
Exit from the service mode.
Monoscope pattern (50 Hz) signal
t
.
A
B
-;II)-
Fig. 6
For the V-AMP 60 Hz, V-LINEARITY 60 Hz, V-OUT PHASE 60 Hi!, and H-POS 60 Hz adjustments, their corrected
data are automatically entered when the corresponding 50-Hz mode adjustments are made. When check these
data on the 60 Hz mode screen, feed the video signal (monoscope pattern 60Hz) via the A/V input jacks. Readjust
any of them if required. (The 50 Hz and 60 Hz modes are selected on the screen.)
Once the adjustment has been made in the 60 Hz mode, do not change it in the 50 Hz mode.
2. FOCUS ADJUSTMENT
1. Receive the monoscope pattern signal.
2. Make the PICTURE ADJUST setting to NORMAL.
3. Adjust the focus control so that the middle areas
between the pattern’s center and the screen’s both
ends be in the best focus.
Fig. 7
17

VT-3448X
VT-51 48X
n PAL CHROMA ADJUSTMENT
1. SUB-COLOUR ADJUSTMENT (12C bus data adjustment)
1. Receive the PAL colour bar signal.
2. Put the set in the service mode.
3. Select the sub-colour mode (COL).
-I
4. Connect the oscilloscope to TP852 (RED cathode).
(Use a 10 : 1 probe.) (TP855 for VT-5148X)
l Range:
20 V/div.
l Sweep time: 20 psec/div.
5. Adjust the sub-colour data so that the 75% white
and red portions of the PAL colour bar be at the
i
-
I
1
-i
J
:Y G
same level. See Fig. 8.
6. Exit from the service mode.
l
When getting out of the SUB-COLOUR mode,
the sub-colour data turns up 15.
,
To be at the same level
Fig. 8
w NTSC CHROMA ADJUSTMENT
1. SUB-TINT ADUJUSTMENT (l*C bus data adjustment)
1. Receive the NTSC colour bar signal.
2. Put the set in the service mode.
3. Select the SUB-TINT mode (TINT).
4. Connect the oscilloscope to TP802 (B-Y OUT).
l Range :
10 mV/div. (AC)
l Sweep time : 10 psec/div.
(Use a 10 : 1 probe.)
5. Adjust the sub-tint data to obtain the waveform
as shown in Fig. 9.
6. Exit from the service mode. About 3 Vp-p
Fig. 9
18

I
VT-3440X
VT-51 48X
n AA/ INPUT AND OUTPUT CHECK
1. VIDEO and AUDIO OUTPUT CHECK
1. Receive the PAL colour bar signal.
(100% white colour bar, 400 Hz, 100% modula-
tion audio)
2. Terminate the video output with a 75fi impedance.
Make sure the output is as specified
(1 .O Vp-p 2 3 dB).
3. Terminate the audio output with a 10k ohm im-
pedance. Make sure the output is as specified (2.6
Vp-p + 3 dB).
l Be sure that the audio output corresponds to
the video output on the screen.
2. VIDEO and AUDIO INPUT CHECK
1. Receive the PAL colour bar.
2.
Feed the video and audio signal via the A/V input
jacks.
3.
Using the CH A/v keys on the remote controller,
change to the AV mode and make sure the exter-
nal video and audio outputs are accordingly given.
(The AV mode can be picked up between ICH
and OCH.)
CHA 99+O+AVl -+AV2+1 +2
CHT 2-31 -+AV2-+AVl -+0-+99
l The AV mode may also be picked up using the
TV/VIDEO key on the remote controller.
n PROTECTOR PERFORMANCE CHECK
--_--------__I
J401 (Rear) - -AVl
J401 (Rear) - -AVl
J402(Front) AV2
1.
BEAM PROTECTOR
1. Receive the monoscope pattern signal.
2. Set the contrast control to maximum.
3. Set the brightness control to maximum.
4. Make a short-circuit between the collector and
emitter of Q853 and make sure that the protector
is activated and the stand-by mode is called. (The
POWER LED indicator starts flashing in red.)
2. HIGH-VOLTAGE PROTECTOR
1. Receive the monoscope pattern signal.
2. Connect the bias box to TP603.
3.
Adjust the bias box voltage to 20 V and make sure
that the protector is not activated.
Note : Normally about 19 V
4.
Adjust the bias box voltage to 25 V and make sure
that the protector is activated.
3. OTHER PROTECTORS
l
In checking the performance of other protectors
- for example, the one against shorting of
smoothing electrolytic capacitor of +B line -, pay
attention not to damage or deteriorate any related
element.
19

VT-3448X
VT-51 48X
n FUNCTION CHECK (1) (VIDEO AND AUDIO)
1. CONTRAST KEY
1. Receive the monoscope pattern signal.
2. Using the PlCTUREADJUSTcontrol, select CON-
TRAST.
3. The contrast must be changeable with the +/- key.
2. COLOUR KEY
1. Receive the PAL colour bar signal.
2. Using the PICTURE ADJUST control, select COL-
OUR.
3. The colour must be changeable with the +/- key.
(There must be no colour at the MIN position.)
R/C ME:NU
KEY
1 -+PICTURE ADJUST
I
1 +CONTRAST
/ -4OLOUR
1 -+Brightness
I
--+TINT
I
-4SHARPNESS
I
3. BRIGHTNESS KEY
1. Receive the monoscope pattern signal.
2. Using the PICTURE ADJUST key, select BRIGHT.
3. The black level must be changeable with the +/-
key.
4. TINT KEY
1. Feed the video signal (NTSC colour bar) Via the AA/ input jacks.
2. Using the PICTURE ADJUST control, select TINT.
3. The tint must be changeable toward green with the + key and toward red with the - key.
5. PIC-NORMAL KEY
1. With the PICTURE ADJUST control, select NORMAL. Make sure the following normal settings are displayed.
Here are the normal settings.
l Contrast : MAX
(60)
l Colour : CENTER (0)
l Brightness : CENTER (0)
l Tint : CENTER
(0)
l Sharpness : CENTER (0)
6. SHARPNESS KEY
1. Receive the monoscope pattern signal.
2. Using the PICTURE ADJUST control, select SHARPNESS.
3. The sharpness must be changeable with the +/- key.
7. CHANNEL SIGH DISPLAY COLOUR
1. The display colour of all the channel (0 - 99) signs must be green1 (AFT off).
20