Sharp 20CT-250 Service Manual
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Sharp 20CT-250 Service Manual

Sharp 20CT-250 Service Manual

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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.
Ë User Preset Timer (On Timer/Sleep Timer/Reminder)
Ë 2 Selectable OSD Languages (English/Thai)
Ë CATV (Hyper Band) Ready
〈Used Frequency Synthesizer Tuner〉
Ë NTSC 4.43/3.58MHz (AV only), Rear AV IN/OUT
terminal
Ë Blue Back Noise Mute
Ë Fine Tuning Adjustable with Remote Control
» SPECIFICATIONS ............................................... 2
» IMPORTANT SERVICE NOTES ......................... 2
» ADJUSTMENT PRECAUTIONS ........................ 3
» SERVICE ADJUSTMENT ................................... 6
» TROUBLE SHOOTING TABLE ......................... 15
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.

SERVICE MANUAL

MODEL
FEATURE
Ë Full Auto Channel Preset And Auto Channel Skip
Ë 100 CH Program Memory
Ë Aperture Control Circuit
Ë Black Stretch Circuit
Ë Bilingual System (Mono)
Ë Auto Channel Scan System
Ë Favorite Channel Memory System
CONTENTS
Page
» CHASSIS LAYOUT ............................................ 17
» SCHEMATIC DIAGRAM ................................... 19
» BLOCK DIAGRAM ............................................ 23
» REPLACEMENT PARTS LIST .......................... 27
WARNING
COLOUR TELEVISION
Chassis No. G2
20CT-250
20CT-250
S88U521CT-250
Page

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Summary of Contents for Sharp 20CT-250

  • Page 1: Table Of Contents

    20CT-250 SERVICE MANUAL S88U521CT-250 COLOUR TELEVISION Chassis No. G2 20CT-250 MODEL 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.

  • Page 2: Specifications

    SPECIFICATIONS Convergence ..............Self Converging System IMPORTANT SERVICE NOTES Focus ................. Uni Bi-Potential Electrostatic Sweep Deflection ..................Magnetic Maintenance and repair of this receiver should be done by Intermediate Frequencies qualified service personnel only. Picture IF Carrier ................. 38.9 MHz Sound IF Carrier Frequency ............

  • Page 3: Adjustment Precautions

    ADJUSTMENT PRECAUTIONS This model’s settings are adjusted in two different ways: through the I C bus control and in the conventional analog manner. The adjustment via the I C bus control includes preset-only items and variable data. 1. Calling the service mode by the microprocessor 1 Set the switch S1006 to the service mode position, and the microprocessor is put in the service mode (adjustment through the I C bus control).
  • Page 4 SUB-ADJUST mode SUB SUBTINT ( SUB TIN) V-PHASE 60 Hz (V-CENTER60) Y DELAY B/W (DT BW TV/AV) SUB SHARPNESS (SUB SHARP) H-PHASE 60 Hz (H-CENTER60) VIDEO MUTE ON/OFF (V-MUTE) In the direction of arrow : CH DOWN key In the opposite direction : CH UP key...
  • Page 5 * To go to the service mode, the data at the E PROM’s addresses 00H thru 03H are read. If the data are not as INITIAL SETTINGS OF CHANNEL SELECTION DATA given below, the E PROM is initialized according to the table below. Address : Data (1) Make an entry of MCL1 in the service mode in order to set the following channel selection data to the...

  • Page 6: Service Adjustment

    PIF/AFT/AGC ADJUSTMENT SERVICE ADJUSTMENT 115V ADJUSTMENT No. Adjusting point Adjusting procedure/conditions Waveform and others VCO adjust- 1. Disconnect the antenna from the tuner antenna * Warm up the unit for longer than No. Adjusting point Adjusting procedure/conditions Waveform and others ment: T203 terminal.

  • Page 7: Purity Adjustment

    PURITY ADJUSTMENT CONVERGENCE ADJUSTMENT No. Adjusting point Adjusting procedure/conditions Waveform and others No. Adjusting point Adjusting procedure/conditions Waveform and others Purity 1. Using the remote controller, make the screen colour Convergence 1. Receive the Crosshatch Pattern signal. adjustment green-only. Adjust the contrast control to have a beam adjustment 2.
  • Page 8 CRT CUT-OFF, SUB-CONTRAST, WHITE BALANCE AND SUB BRIGHTNES ADJUSTMENT No. Adjusting point Adjusting procedure/conditions Waveform and others No. Adjusting point Adjusting procedure/conditions Waveform and others Maximum 1. Receive the Monoscope Pattern signal. beam current 2. Set to the P-NORM mode. CRT cut-off 1.
  • Page 9 PAL CHROMA ADJUSTMENT PROTECTOR PERFORMANCE CHECK No. Adjusting point Adjusting procedure/conditions Waveform and others No. Adjusting point Adjusting procedure/conditions Waveform and others Sub-colour 1. Receive the PAL Colour Bar signal. Beam protector 1. Receive the Monoscope Pattern signal. adjustment: 2. Set to the P-NORM mode. 2.
  • Page 10 FUNCTION CHECK (VIDEO AND AUDIO) No. Adjusting point Adjusting procedure/conditions Waveform and others No. Adjusting point Adjusting procedure/conditions Waveform and others Contrast key 1. Receive the E-5CH signal. Channel sign 1. The display colour of all the channel (0-99) signs 2.
  • Page 11 MEMORY MAP (RH-iX3031CEZZ) DATA DATA FACTORY FACTORY REMARKS CRITERIA REMARKS CRITERIA ADDRESS SETTING ADDRESS SETTING Initialization judgment data “23” Other than $23 PLL data (upper) CH22 Initialization judgment data “20” Other than $20 PLL data (lower) Initialization judgment data “13” Other than $13 PLL data (upper) CH23...
  • Page 12 DATA DATA FACTORY FACTORY REMARKS CRITERIA REMARKS CRITERIA ADDRESS SETTING ADDRESS SETTING PLL data (upper) CH46 PLL data (upper) CH70 PLL data (lower) PLL data (lower) PLL data (upper) CH47 PLL data (upper) CH71 PLL data (lower) PLL data (lower) PLL data (upper) CH48 PLL data (upper)
  • Page 13 DATA DATA FACTORY FACTORY REMARKS CRITERIA REMARKS CRITERIA ADDRESS SETTING ADDRESS SETTING PLL data (upper) CH94 CH7 CH5 CH5 CH4 CH3 CH2 CH1 CH0 SKIP SKIP ON PLL data (lower) CH15 CH5 CH5 CH4 CH3 CH2 CH1 CH0 0 : OFF PLL data (upper) CH95 CH23 CH22 CH21 CH20 CH19 CH18 CH17 CH16...
  • Page 14 DATA DATA FACTORY FACTORY REMARKS CRITERIA REMARKS CRITERIA ADDRESS SETTING ADDRESS SETTING AUDIO SYSTEM (1) VIDEO SYSTEM (2) AUTO P/N KIL NOISE DET RGB CONTRAST Y γ WPL SW AFC MODE B.S OFF P/N GP CL-L SW 0,0,1 CLL LEVEL PN CD ATT BLACK STRETCH OFFSET DC TRAN RATE...

  • Page 15: Trouble Shooting Table

    TROUBLE SHOOTING TABLE TROUBLE SHOOTING TABLE (Continued) NO RASTER CIRCUITS TO BE CHECKED: NO PICTURE, NO SOUND » Tuner. » PIF. Check F701. Blown out. » Automatic Gain Control. » (5V), (9V) Power Source. Does the noise level increase at max. Contrast, Brightness and Sound controls ? Normal Replace the fuse.
  • Page 16 TROUBLE SHOOTING TABLE TROUBLE SHOOTING TABLE (Continued) (Continued) NO SPECIFIC COLOUR NEITHER VERTICAL NOR HORIZONTAL SYNCHRONIZATION Is some colour produced in CIRCUIT TO BE CHECKED: B/W broadcast reception ? » Sync. Separator Circuit. Check IC801 and Q401. Is the white balance properly Check IC801, R809, R810, adjusted ? R811, D801, D802, D803,...

  • Page 17: Chassis Layout

    20CT-250 CHASSIS LAYOUT 21CT-25 as is...

  • Page 18: Solid State Device Base Diagram

    20CT-250 SOLID STATE DEVICE BASE DIAGRAM TOP VIEW ST24C04 iX1779CE TB1226 iX3031 BA7357S SIDE VIEW BASE CATHODE COLLECTOR BASE 1 2 3 3 2 1 E C B ANODE EMITTER COLLECTOR EMITTER 2SA1015 KiA7045P UPC78L05 iX0037CE 2SC3789 TA7348P 2SC2482 2SC1815...
  • Page 19 20CT-250 20CT-250 Ë Ë Ë Ë Ë Tuner DESCRIPTION OF SCHEMATIC DIAGRAM å å å å å RTUNQ0004KJZZ NOTE: The parts here shown are supplied as an assembly but not independently. SAFETY NOTES: NOTES: 1. DISCONNECT THE AC PLUG FROM THE AC OUTLET BEFORE 1.

  • Page 20: Schematic Diagram

    20CT-250 20CT-250 SCHEMATIC DIAGRAM...

  • Page 21: Block Diagram

    20CT-250 20CT-250 BLOCK DIAGRAM...
  • Page 22 20CT-250 20CT-250 PRINTED WIRING BOARD ASSEMBLIES (All the PWBs here are shown as viewed from their wiring sides) 21CT-25 as is (K9399WE) PWB-B: CRT Socket Unit 21CT-25 as is (K9398WE) PWB-A: Main Unit...

  • Page 23: Printed Wiring Board Assemblies

    20CT-250 Ref. No. Part No. Description Code Ref. No. Part No. Description Code PARTS LIST PWB-A: DUNTK9398WET4 PARTS REPLACEMENT MAIN UNIT Replacement parts which have these special safety characteristics identified in this manual: electrical components having such features TUNER are identified by "å" in the Replacement Parts Lists.
  • Page 24 20CT-250 Ref. No. Part No. Description Code Ref. No. Part No. Description Code COILS AND TRANSFORMERS PWB-A: DUNTK9398WET4 CF201 RFiLA0042CEZZ R Filter MAIN UNIT (Continued) CF202 RFiLA0095CEZZ R Filter D302 RH-DX0224CEZZ R Diode CF203 RFiLC0411CEZZ R Filter D303 RH-DX0475CEZZ R Diode...
  • Page 25 20CT-250 Ref. No. Part No. Description Code Ref. No. Part No. Description Code PWB-A: DUNTK9398WET4 C504 VCCSPA2HL471K R 470p 500V Ceramic C505 RC-QZA104TAYK R 0.1 Mylar MAIN UNIT (Continued) C506 VCEAGA1EW108M R 1000 Electrolytic C225 VCKYPA1HF103Z R 0.01 Ceramic C507...
  • Page 26 20CT-250 Ref. No. Part No. Description Code Ref. No. Part No. Description Code PWB-A: DUNTK9398WET4 C1020 VCEAGA0JW107M R 100 6.3V Electrolytic C1021 VCCSPA1HL181J R 180p Ceramic MAIN UNIT (Continued) C1022 VCKYD41CY103N R 0.01 Ceramic C723 VCKYPA2HB102K R 1000p 500V Ceramic å...
  • Page 27 20CT-250 Ref. No. Part No. Description Code Ref. No. Part No. Description Code PWB-A: DUNTK9398WET4 R613 VRD-RA2BE103J R 10k 1/8W Carbon R614 VRD-RM2HD180J R 18 1/2W Carbon MAIN UNIT (Continued) R617 VRS-VV3AB330J R 33 Metal Oxide R303 VRD-RA2BE392J R 3.9k 1/8W...
  • Page 28 20CT-250 Ref. No. Part No. Description Code Ref. No. Part No. Description Code PWB-A: DUNTK9398WET4 R1052 VRD-RA2BE272J R 2.7k 1/8W Carbon R1055 VRD-RM2HD101J R 100 1/2W Carbon MAIN UNIT (Continued) R1057 VRD-RA2BE273J R 27k 1/8W Carbon R1058 VRD-RA2BE822J R 8.2k 1/8W...

  • Page 29: Miscellaneous Parts

    20CT-250 Ref. No. Part No. Description Code Ref. No. Part No. Description Code PWB-B: DUNTK9399WET4 MISCELLANEOUS PARTS CRT UNIT å QACCZ3008PEZZ J AC Cord ACC701 TRANSISTORS RSP-Z0003KJZZ Speaker Q851 VS2SC3789//1E R 2SC3789 RSP-Z0003KJZZ Speaker Q852 VS2SC3789//1E R 2SC3789 Q853 VS2SC3789//1E...

  • Page 30: Sharp Corporation

    Code Ref. No. Part No. Description Code COPYRIGHT © 1998 BY SHARP CORPORATION ALL RIGHTS RESERVED. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of the publisher.

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