Sharp 37VT-26H User manual

1
37VT-26H(GY)
WARNING
Thechassisinthisreceiverispartiallyhot.Useanisolationtransformerbetweenthelinecordplugandpower
receptacle,whenservicingthischassis.Topreventelectricshock,donotremovecover.Nouser– serviceable
parts inside. Refer servicing to qualified service personnel.
SERVICE MANUAL
S99P337VT26H/
In the interests of user-safety (Required by safety regula-
tions in some countries) the set should be restored to its
originalcondition and onlyparts identical tothose specified
be used.
MODEL
SERVICE MANUAL TV/VCR COMBINATION TELEVIDEO MODEL 37VT-26H(GY)
SHARP CORPORATION
37VT-26H(GY)
TV/VCR COMBINATION
TELEVIDEO
Chassis No.VP-8
37VT-26H(GY)
FEATURE
ËAIS (Automatic Instruction System)
ËASS (Automatic Sorting System)
ËVPS/PDC (Video Program System / Program Delivery
Control)
ËFASTEXT
ËVIDEO Plus+
ËPost Cord Security
ËOn Screen Digital Channel/Sound Level/Tuning Display,
Control (Contrast, Colour, Brightness, Tint, Sharpness,
White temp) Symbol and Level
ËBlue Back OffTimer
Ë52 Key, Wireless Remote Control Unit
ËChannel Skip
ËHigh Speed and Double Speed Video Search System
»PAL : 3 times/7 times (SP/LP)
»NTSC : 3 times/5 times (SP/LP)
5 times/15 times (EP)
ËDPSS (Digital Program Search System)
ËQuick Start Playback with Full Loading System
ËDigital Automatic Tracking Control
ËAutomatic Playback Function
ËAHC (Automatic Head Cleaning System)
ËSharp Super Picture
Ë345 Times Hi-Speed FF/REW
CONTENTS Page
»SPECIFICATIONS ................................................................................................................................................................................. 2
»IMPORTANT SERVICE NOTES ............................................................................................................................................................ 3
»LOCATION OF USER'S CONTROL...................................................................................................................................................... 4
»DISASSEMBLY AND REASSEMBLY .................................................................................................................................................... 6
»ADJUSTMENT OF THE TV ELECTRICAL CIRCUITRY ........................................................................................................................9
»PRECAUTIONS IN REASSEMBLING ................................................................................................................................................ 19
»FUNCTION OF MAJOR MECHANICAL PARTS ................................................................................................................................. 20
»ADJUSTMENT, REPLACEMENT AND ASSEMBLY OF MECHANICAL UNITS ................................................................................. 22
»ADJUSTMENT OF THE VCR ELECTRICAL CIRCUITRY ...................................................................................................................41
»MECHANISM OPERATION FLOWCHART AND TROUBLESHOOTING GUIDE ............................................................................... 44
»CHASSIS LAYOUT .............................................................................................................................................................................. 63
»BLOCK DIAGRAM OFTV SECTION .................................................................................................................................................. 64
»BLOCK DIAGRAM OFVCR SECTION ............................................................................................................................................... 66
»DESCRIPTION OF SCHEMATIC DIAGRAM ...................................................................................................................................... 75
»SOLID STATE DEVICE BASE DIAGRAM ........................................................................................................................................... 76
»WAVEFORMS .....................................................................................................................................................................................77
»SCHEMATIC DIAGRAM ...................................................................................................................................................................... 78
»PRINTED WIRING BOARD ASSEMBLIES......................................................................................................................................... 92
»REPLACEMENT PARTS LIST ............................................................................................................................................................ 99
»PACKING OF THE SET ..................................................................................................................................................................... 115

37VT-26H(GY)
2
SPECIFICATIONS
ËOUTLINE OFTHE PRODUCT
Power Source: 220~240 V AC, 50 Hz
Power Consumption: 77 W
Receiving Broadcast Standard: I
Receiving Channel: VHF; 1A~S36
UHF; S37~C57
Receiving System: Sound; 6.0 MHz
Colour; PAL
Antenna Input Impedance: VHF/UHF; 75 ohm Unbalanced (DIN)
Video Signal: Input; 0.5-2.0 Vp-p/75 ohm (SCART/RCA)
Output; 1.0 Vp-p/75 ohm (SCART)
Audio Signal: Input; 0.5 Vrms/10k ohm (SCART/RCA)
Output; 0.5 Vrms/1k ohm (SCART) (54% MOD)
Temperature: Operation; 5°C to 40°C
Storage; -10°C to 60°C
Dimensions (Approx.): 378 mm (W) ×387 mm (H) ×384 mm (D)
Weight (Approx.): 12.7 kg
Cabinet Material: Plastic
Accessories: Operation Manual
Infrared Remote Control Unit
Dry Batteries, Type AA (×2 pcs.)
ËTV SECTION
Viewing Area: 33.54 cm Diagonal Measurement
Picture Power: 22.0 kV at 800 µA Beam Current
Speaker Output: 3.0 W at Max.(5×9 cm oval type ×1pc.)
Picture Tube: Type; VB370BVBK1S-S (Tint Tube)
Heater; 6.3 V, 300 mA
Focus; High Bi-Potential Electrostatic
ËVCR SECTION
Outline: VHS Video System ColourVideo Cassette Recorder
Format: VHS PAL/NTSC Standard
Video Recording System: Rotary Slant Azimuth 2-Head Helical Scan System
Luminance: FM Recording
Chrominance: Low Frequency Converted Direct Recording
Video Signal System: PAL/NTSC 3.58MHz Colour
Cassette Tape: VHS Type Video Cassette Tape
Tape Width: 12.7 mm
Tape Speed: 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)
Recording/Playback Time: 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)
Number of Video Head: 4 pcs.
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.

3
37VT-26H(GY)
IMPORTANT SERVICE NOTES
Maintenance and repair of this receiver should be done by qualified service
personnel only.
SERVICING OF HIGHVOLTAGE SYSTEM AND PIC-
TURETUBE
When servicing the high voltage system,remove static charge from it by con-
necting a 10k 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. When repairing the circuit, be sure not to increase the high voltage to more than 25.3 kV,
(at beam 0 µA) for the set.
2. 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 µA) 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 RETURNINGTHE 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.

37VT-26H(GY)
4
LOCATION OF USER'S CONTROL

5
37VT-26H(GY)
LOCATION OF USER'S CONTROL (CONTINUED)

37VT-26H(GY)
6
1. Remove the 11 rear cover fixing screws and detach the rear cover.
2. Take out the anode cap, CRT PWB, connectors H, G and F, coating ground, SP chip, fixing screws and others.
3. Remove the Main PWB fixing screws and take out the Main PWB unit and the Power PWB.
4. Remove the 4 Power PWB fixing screws, and take out the Power PWB unit.
DISASSEMBLY AND REASSEMBLY
G
F
H
3
2
4
1
1

7
37VT-26H(GY)
DISASSEMBLY AND REASSEMBLY (CONTINUED)
5. Remove the 8 VCR 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 7 mechanism chassis fixing screws, and detach the mechanism chassis from the Main PWB.
8. Remove the 3 Main PWB fixing screws, and detach the Main PWB.
9. Remove the 2 Tuner/Def and IF PWB fixing screws, and detach the Tuner/Def and IF PWB.
5
6
7
7
7
7
8
9

37VT-26H(GY)
8
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.
DISASSEMBLY AND REASSEMBLY (CONTINUED)
AO
AJ
H
PC
PC
K
AV
A
A
F
G
S
AJ
S
K
F
H
AV
PA
PB
PB
PA
AB
G
AB
70~80°
Note: Fit the VCR unit the front cabinet with the front flap door tilted at 70~80°.

9
37VT-26H(GY)
ADJUSTMENT OFTHETV ELECTRICAL CIRCUITRY
ADJUSTMENT PRECAUTIONS
1. Calling the service mode
Get the service test points (TP2002 and TP2003) of the set short-circuited.
2. Getting out of the service mode
Get the above service test points open.
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.
Service mode
Item Display Data Variable range
DIRECT MODE →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 0 ~ 7 B CUT OFF (0 ~ 255)
H-POSITION H-POS 0 ~ 31 G DRIVE GAIN (0 ~ 255)
BELL FILTER BELL 0 ~ 3 B DRIVE GAIN (0 ~ 255)
R-Y BLACK OFFSET R-Y 0 ~ 15
B-Y BLACK OFFSET B-Y 0 ~ 15
Y-SUB CONTRAST CONT 0 ~ 31
SUB COLOUR COLOR 0 ~ 240
SUB BRIGHT BRI 0 ~ 150
SUB TINT TINT 0 ~ 37
Top line : Service mode item (See below)
Micon version display
Bottom line : Data (See below)
Note :
Item selectable by the CH '" keys and data by the VOL '" 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.
UP DOWN
R CUT OFF 1 4
G CUT OFF 2 5
B CUT OFF 3 6
G DRIVE GAIN 7
õ
Õ
B DRIVE GAIN 8 0
Notes :
In all the other modes, these keys are used to select channels.
In the DIRECTTUNING mode, these keys are used to enter data.

37VT-26H(GY)
10
Item-by-item control in the service mode
1. DIRECT mode F-B/W 0 - > 1 (forced B/W)
2. DIRECT mode + HOR. POS. mode DRV CNT 0 - > 1 (drive forced center)
SUB-BRIGHT Initial value
R.G.B. CUTOFF 0 (E2PROM data resumed when any of the “0” thru
“9” keys on the remote controller is pressed)
3. R-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
4. B-Y Black Offset 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 MAX./MIN. select key TIMER ON/OFF
`DIRECT TUNING MODE KEY RETURN
`VCR SLOWTEST 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) LED (red) flashing : Deflection system protector activated (high-voltage or beam vert, out protector)
2) REC LED flashing : IIC bus line error (VCJ or tuner, EEPROM, TEXT, PDC)
3) LED off : Power protector activated (+B line short-circuited)