Service Manual COMMODORE 1701/1702 MONITOR

SERVICE MANUAL MODEL 1701/1702 MONITOR Preliminary APRIL 1985 PN-314004-01 Commodore Business Machines, Inc. 1200 Wilson Drive, West Chester, Pennsylvania 19380 U.S.A. Commodore makes no expressed or implied war- ranties with regard to the information contained herein. The information is made available solely on an as is basis, and the entire risk as to quality and accuracy is with the user. Commodore shall not be liable for any consequential or incidental damages in connection with the use of the information contained herein. The listing of any available replacement part herein does not constitute in any case a recommendation, warranty or guaranty as to quality or suitability of such replacement part. Reproduction or use without expressed permission, of editorial or pictorial content, in any matter is prohibited. This manual contains copyrighted and proprietary information. 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 the prior written permission of Commodore Electronics Limited. Copyright © 1985 by Commodore Electronics Limited. All rights reserved.

CONTENTS Title Page SPECIFICATIONS SAFETY PRECAUTIONS ......................................................................................... 2 ADJUSTMENTS PURITY ...................................................................................................... 4 CONVERGENCE ... ........................ .............. .............. ........................ .... ........ 5 WHITE BALANCE ........................................................................................ 5 B1 VOLTAGE, FOCUS, VERT. & HOR. ADJ. ................................................... 6 SUB TINT, SUB CONTRAST, COLOR SYNC, 3.58 MHz TRAP ........................... 7 BLOCK DIAGRAM CIRCUIT NOTES 8 VIDEO CIRCUIT ....... ............ ... ................... ........ ................... ................ .... ... 9 AUDIO CIRCUIT ............ ......... .......... ........................ .... ....... .... ... ................. 10 COLOR DEMODULATION CIRCUIT ................................................................ 11 CHROMA OUTPUT CIRCUIT ................................................... ........ .... ....... ... 12 CONTROL CIRCUIT .......................................................................... ............ 13 H. OSC., V. OSC. & V. OUT CIRCUIT ................ ...................... ...................... 14 HORIZONTAL OUTPUT CIRCUIT ................................................................... 15 POWER CiRCUiT ........................................................................................ , 16 TROUBLESHOOTING GUIDE NO RASTER, NO SOUND (81 NORMAL) .............. .......... .......... .............. ........ 17 NO RASTER, NO SOUND (81 ABNORMAL) ...... ........................ .............. ........ 18 NO RASTER, NORMAL SOUND .............................................. ' ............. , ........ 19 NO SOUND, NORMAL PICTURE ................................................. , .................. 19 SINGLE HORIZONTAL LINE, NORMAL SOUND ....... .............. ........................... 20 IMPROPER HORIZONTAL OR VERTICAL SYNC ...... ........ .......... ....................... 22 1701 PARTS LIST ........ ......................... ..... ............. .......................... ... ......... ........ 23 1701 BOARD LAYOUT ................................... ............................ .......... ........... ...... 30 1701 SCHEMATIC NOTES ..................................................................................... 31 1701 SCHEMATIC ................................................................................................ 31 iii

.-----~-~--~------ CONTENTS (Continued) Title Page TROUBLESHOOTING GUIDE - 1702 32 DEAD SET, B+ ABNORMAL ......................................................................... 33 NO RASTER, SOUND NORMAL, HIGH VOLTAGE NORMAL .............................. 34 NO RASTER, NO SOUND, B+ NORMAL ........................................................ 35 NO CHROMA, SOUND NORMAL, BLACK & WHITE TRACKING ......................... 36 NO VIDEO, SOUND NORMAL, RASTER NORMAL ...................... ...................... 37 NO SOUND, VIDEO NORMAL ....................................................................... 38 NO VERTICAL SWEEP .................................................................................. 38 CANNOT SET BLACK & WHITE TRACKING .................................................... 39 1702 MODEL IDENTIFICATION ............................................................................... 40 1702 PARTS LIST ................................................................................................. 41 1702 BOARD LAYOUT .......................................................................................... 48 1 702 SCHEMATIC NOTES ..................................................................................... 49 1702 SCHEMATIC ................................................................................................ 49 1 702T BOARD LAYOUT ........................................................................................ 50 1702T UNIQUE PARTS .......................................................................................... 51 1702T SCHEMATIC .............................................................................................. 51 iv

GENERAL DESCRIPTION C1701/C1702 COLOR MONITORS PRODUCT SPECIFICATION The C1701 and C1702 are quality, high resolution color monitors, designed to maximize the video capabilities of your Commodore Computer. They give you a superior color picture that enhances your computing experience and are completely compatible with all Commodore equipment. SCREEN SIZE 13 Inch (screen measured diagonally). NTSC color standard DISPLAY 40 Columns x 25 lines RESOLUTION 1000 Characters per screen CONTROLS Color, tint, brightness, contrast, volume, vertical hold and horizontal hold AUDIO Built-in audio amplifier and speaker INPUTS Chrominance, luminance, composite video and audio OTHER FEATURES Video cassette recorder compatible (1 V p-p, 75 Ohms) COMPUTERS Commodore 64, VIC 20, Plus/4 and C16 POWER REQUIREMENTS 120 Volts, 60 Hz, 0.85 Amps POWER CONSUMPTION 87 Watts All specifications subject to change without notice. 1

SAFETY PRECAUTIONS 1 . This product contains special designed circuits and components that were designed for safety purposes. For continued protection, changes should not 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 to the design or circuitry of this receiver should not be made. Any design alterations or additions will void the manufactuer'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 MONITOR sets 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, watt- age, etc. Replacement parts which have these special safety characteristics are identified in the parts list of this service manual. Electrical components having such features are identified by shading on the schematics and by (*) on the parts list in this 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 may create shock, fire, or other hazards. 4. If any repair has been made to the chassis, it is recommended the the B1 setting be checked or adjusted (See ADJUSTMENT OF B1 VOLTAGE). 5. The high voltage applied to the picture tube must conform with that specified in this 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 deter- mine 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 alter- natives approved by the manufacturer of the complete product. 6. 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 1 OkQ 2W resistor to the anode button. 7. 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. 2

SAFETY PRECAUTIONS (Continued) 8. ISOLATION CHECK (SAFETY FOR ELECTRICAL SHOCK HAZARD) After re-assembling the product, always perfrom an isolation check on the exposed metal parts of the cabinet, screwheads, cable jacks, controls 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 1,1 OOV AC (r.m.s.) for a period of one second. This method of test requires test equipment not generally found in the service trade. * (8) 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. ALTERNATE CHECK METHOD Plug the AC line cord directly into the AC output (do not use a line isolation transformer during this check). Use an AC voltmeter having 1,000 ohms per volt or more sensitivity in the following manner. Connect a 15000 10W resistor paralleled by a 0.15/LF 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 0.35V AC (r.m.s). This corresponds to 0.5mA AC (r.m.s.). CAUTION: When troubleshooting, with power applied, use an isolation transformer and confirm that the CRT earth wire is connected to the CRT socket board and the chassis. 3

ADJUSTMENTS - PURITY, CONVERGENCE AND WHITE BALANCE PICTURE TUBE The picture tube is a precision in-line gun type. For this picture tube, dynamic convergence is carried out by a precision deflection yoke which eliminates the use of a convergence yoke and a convergence circuit. The adjustment of the picture tube is therefore made easier as only the adjustment of static convergence by using a magnet is enough. The deflection yoke and purity/convergency magnets assembly has been set at the factory and requires no field adjustments. However, should the assembly be accidentally jarred or tampered with, some or all adjustment may be necessary. COLOR PURITY & VERTICAL CENTER Loosen yoke retaining clamp (Fig. 2-1). With a sharp knife, cut between the picture tube and the wedge. Remove wedges completely and clean off dried adhesive from the picture tube. PAINT is used to lock the tabs of the purity/ convergence magnet assembly in place (Fig. 2-1). The paint must be removed with the end of a screwdriver before any adjustments are attempted. 1. Inject a Video Signal (RASTER) to the Video input terminal. 2. Let the purity tabs come in line horizontally as is shown in Fig. 2-3. A long tab should be in the same direction as the other short tab. 3. Move the yoke slowly backward. 4. Turn the green cut-off control to maximum and the red and blue cut-off controls to minimum. Then adjust the screen control so that the green band can be seen best. (Fig. 2-4) 5 . Rotate the two tabs in the opposite direction with them kept at an angle. Move them in either direction so that the green band is centered on the picture tube. 6 . Check the vertical center position by displaying a horizontal line. If incorrect, bring it to the center by rotating the two tabs, kept at an angle, together in either direction. (Fig. 2-5, 2-6) 7. Repeat steps 5 and 6 alternately until the green band and the vertical centre are in line. 8. Move the yoke slowly towards the bell of the tube so that the whole surface of the picture tube is filled with a pure green raster. 9. Turning the red cut-off control to maximum and the green cut-off control to minimum, check for pure red raster. 10. Turning the blue cut-off control to maximum and the green cut-off control to minimum, check for pure blue raster. 11. Secure yoke retaining clamp (do not install wedges at this time). YOKE LOCKING RING PURITY MAGNETS (mark "P") Fig. 2-1 (REAR VIEW) LONG AND SHORT PROTRUSIONS Let the protrusions come in line Fi g .2- 3 J (FRONT VIEW) _-o--7"7t7::,.,-_.L GREEN BAN D CENTRE Bring the green band to the centre. Fig. 2-4 (FRONT VIEW) HORIZONTAL LINE (~~--'------------~ (identified with a white notch) Bring the horizontal line nearest to the white notches shown in the dotted circles. Fig. 2-5 (TOP VIEW) RDG. IJL-___ --I Select the cut-off service switch from N to S, and a horizontal line will appear. Fig. 2-6 4

STATIC CONVERGENCE & DYNAMIC CONVERGENCE Static convergence is achieved by four magnets located on the neck, nearest the base of the picture tube. The front pair of magnetic rings (closest to the purity tabs) are adjusted to converge the red and blue crosshatch lines. The rear pair of convergence rings (closest to the base of the picture tube) are adjusted to converge the magenta (Red/Blue) and green crosshatch lines. Dynamic convergence is achieved by tilting the deflection yoke, Up-Down and Left-Right. 1. Inject Video Signal (CROSSHATCH) to the Video input terminal and adjust BRIGHTNESS and CONTRAST control for distinct pattern. 2. Adjust the convergence around the edges of the picture tube tilting the yoke, up-down and left-right. Temporarily install one wedge at the top of the yoke. (Fig. 2-9, 2-10, 2-11) 3. Rotate the front pair of tabs as a unit to minimize the separation of the red and blue lines around the center of the screen. To adjust the convergence of red and blue, vary the angle between the tabs. 4. Rotate the rear pair of tabs as a unit to minimize the separation of the magenta and green lines. (Fig. 2-8) 5. Adjust the spacing of the rear tabs to converge the magenta and green lines. 6. Apply paint to fix 6 magnets. 7. Remove the wedge installed temporarily on the yoke. 8. Tilting the angle of the yoke up, down and sideways, adjust the yoke so as to obtain the circumference convergence. (Fig. 2-10, 2-11) 9. Insert three wedges to the positions as shown in Fig. 2-12 to obtain the best circumference convergence. 10. Secure wedges in position with the adhesive backing provided or use a non-conductive siliconlrubber compound. 11. White balance adjustment (Black & White tracking) can now be performed. WHITE BALANCE ADJUSTMENT (Black and White Tracking) 1. Inject a Video Signal (RASTER) to the Video input terminal. 2. Set the red and green drive controls for their mechanical center. 3. Turn the red, green and blue cut off controls and the screen control fully counterclockwise. 4. Change the service switch as shown in Fig. 2-6, to the "S" position. 5. Turn screen control slowly clockwise until a very faint horizontal line appears. 6. Turn the cut off control of the color which has ap- peared first, clockwise by about 10 0 and then adjust the screen control again so that the color may shine faintly. 7. Turn the other color cut off controls slowly clockwise until a reasonable white line appears. 8. Return the service switch to normal (N) position. (Fig. 2-6) 9. Adjust the red and green drive controls for best white highlights. (FRONT VIEW) (FRONT VIEW) RED AROUND~. BLUE CENTRE ' , , ~ 1ROUND-~ G~.EEN \ CENTRE __ :': MAGENTA I -•.. - I ' .... , " "------ Fig. 2·7 Fig. 2-8 BLUE GREEN - RED - - (REAR VIEW) W ,..WEDGE 0) ! " DEF. YOKE Fig. 2-9 (FRONT VIEW) RED. GREEN BLUE , , I " " /'f" ,,~, .. ...... - /~ I " ./-', '\.,\j /1 ' . "- BLUE GREEN RED RED - GREEN _BLUE Tilting the yoke upward will move the lines as shown with the arrows. Fig. 2-10 (FRONT VIEW) GREEN BLUE BLUE GREEN RED, ; , ! /RED ; I ; l' ' 1 ' RED __ ::::-_:_-=--=~=-:.:_:~ __ :_ -::: GREEN I I : + : I' BLUE ..,Ii:'" .,.' I .. I • ' I --t l.- ____ = _____ Jl. -~~~~N ~r.----~--'-:- +- RED Tilting the yoke upward will move the lines as shown with the arrows. Fig. 2-11 (REAR VIEW) ANODE CAP Fig, 2-12 5

NOTE: 1702 locations in ( ). B1 VOLTAGE - Inject a video signal 1701 (110V) Regulate VR, R109, for B1 adjustment so that Dc voltage between TP-91 and earth is 110 volts. 1702 (125V.) Confirm that the voltage at TP-94 and IC901 pin 4 is 125 volts. NOTE: Meter should be periodically calibrated at 20K ohms/volt. FOCUS Adjust the FOCUS control for best overall definition and picture detail at normal brightness and contrast. VERTICAL POSITION Adjust the V. center VR R428 (R429) to the optimum vertical picture position. VERTICAL HEIGHT AND LINEARITY 1 . Display a pattern which allows easy confirmation of symmetry (such as a circle or crosshatch). 2. Reduce the vertical size with the V. HEIGHT VA. 3. Adjust the vertical linearity with the V. LIN. VA. 4. Readjust the vertical height, so that the picture extends to normal size. HORIZONTAL WIDTH Adjust H. WIDTH control coil L503 (L522) by turning it with a hexagonal adjusting bar only if RIGHT and LEFT sides of picture can't be seen. HORIZONTAL OSCILLATOR 1. Set the H. FREQ. VR to the mechanical center position. 2. Connect a jumper clip between TP-33A and TP-33B. 3. While rotating the H. FREQ. VR, R504, keep the picture stationary or slowly moving. 4. Remove the jumper wire. 5. Make sure that the set maintains horizontal sync, when signals are switched. 6

Service Manual COMMODORE 1701/1702 MONITOR

You're Reading a Preview

Recently Viewed