COMMODORE C64 C64C Service Repair Fix Manual

SERVICE MANUAL C64/C64C MARCH, 1992 PN-314001-03 Commodore Business Machines, Inc. 1200 Wilson Drive, West Chester, Pennsylvania 19380 U.S.A. Commodore makes no express or implied warranties with regard to the information contained herein. The information is made available solely on an as is basis, and the entire risk as to completeness, reliability, and accuracy is with the user. Commodore shall not be liable for any 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 express 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, photo copying, recording or otherwise, without the prior written permission of Commodore Electronics Limited. Copyright © 1992 by Commodore Electronics Limited. All rights reserved. Printed in U.S.A.

CONTENTS Title Page SPECIFICATIONS 1 PRODUCT PARTS LIST 2 BLOCK DIAGRAM 3 CIRCUIT THEORY POWER SUPPLY 4 RESET LOGIC 5 CLOCK CIRCUITS 6 I/O, ROM, EXPANSION PORT 7 RAM CONTROL LOGIC 8 5 PIN VIDEO AND AUDIO OUTPUTS 9 8 PIN VIDEO AND AUDIO OUTPUTS 10 CASSETTE INTERFACE 11 KEYBOARD, JOYSTICK & PADDLE INTERFACES 12 SERIAL INTERFACE, USER PORT 13 TROUBLESHOOTING GUIDE 14 BOARD IDENTIFICATION 17 PCB ASSEMBLY #326298-01 BOARD LAYOUT 18 PARTS LISTS 19,20 PIN ASSIGNMENTS 21 SCHEMATIC #326106 21,22 PCB ASSEMBLY #250407-04 BOARD LAYOUT 23 PARTS LIST 24,25 MODULATOR SCHEMATIC #251025 26 SCHEMATIC #251138 26,27 PIN ASSIGNMENTS 27 PCB ASSEMBLY #250425-01 BOARD LAYOUT 28 PARTS LIST 29,30 MODULATOR SCHEMATIC #251696 31 SCHEMATIC #251469 31,32 PIN ASSIGNMENTS 32

CONTENTS (continued) Title Page SERVICE REFERENCE DIAGRAM B-3 33 B-3 PCB PARTS LIST 34 B-3 BOARD LAYOUT 36 B-3 SCHEMATICS #252278 37 SERVICE REFERENCE DIAGRAM - E 39 E PCB PARTS LIST 40 E BOARD LAYOUT 41 E SCHEMATIC #252312 42

C64 GENERAL DESCRIPTION MEMORY ROM MICROPROCESSOR DISPLAY COLORS CHARACTERS DISPLAY MODES RESOLUTION SPRITES SOUND KEYBOARD KEYS INPUTS/OUTPUTS FEATURES PERIPHERALS POWER REQUIREMENTS COMPUTER • The "All Purpose" Commodore 64 is the complete computer for education, home or small business applications. Supported by quality peripherals and a full range of software, the Commodore 64 is perfect for the family. No other computer can offer such variety of uses and applications at such an affordable price. • 64K RAM • 20K ROM Standard (includes operating system and BASIC interpreter) • 6510A Microprocessor—1.02 MHz clock • Compatible with the 6502 • 40 Columns X 25 lines of text • 16 Background, border and character colors • Upper & lower case letters, numerals and symbols • Reverse characters • All PET graphic characters • Text characters • High resolution graphics • 320 X 200 Pixels • 8 independent sprites • Each consists of 24 X 21 pixels and up to 4 colors • Each independently expandable horizontally and vertically • Collision detection for sprite to sprite and data to sprite collisions • 6581 Sound Interface Device includes 3 independent tone generators—each with 9 octaves • Each voice includes programmable ADSR generator (Attack, Decay, Sustain, Release) and control of sawtooth, triangle, square, variable pulse and noise waveforms • Full filtering capabilities with low, high and band pass filters • External sound input • Full size typewriter style design • 66 Keys total • 2 Cursor control keys • 4 Function keys (up to 8 user defined/programmable functions possible) • Upper and lower case character set • Graphic character set • User port • Serial port • ROM cartridge port • 2 Joystick/ paddle ports • Video port • C1530 Cassette drive interface port • Built-in BASIC 2.0—over 70 commands, statements and functions • Full screen editor • C1541 Diskdrive • C1530 Datasette • MPS 801 Dot matrix printer • MPS 802 Dot matrix printer • MPS 803 Dot matrix printer • DPS 1101 Daisey wheel printer • C1520 Plotter/Printer • C1702 Color monitor • CM 141 Color monitor • 120 Volts, 60 Hz Specifications subject to change without notice.

PARTS LIST C64 NOTE: Commodore part numbers are provided tor reference only and do not _._ availability of parts from Commodore. Industry standard parts (Resistors, "', Connectors) should be secured locally. Approved cross-references tor TTL chips, are available in manual form through the Service Department, order part 1. Unique or non-standard parts will be stocked by Commodore and are indicated bya"C". TOP CASE ASSY L Top Case Keyboard LED Plate Nameplate Lamp Holder Set LED Assembly BOTTOM CASE ASSY Bottom Case Foot, Self-Adhesive PCB Shield Plate PCB Insulation Sheet ACCESSORIES Users Manual Power Supply RF Cable Switch Box C C C C C C 326113-01 326165-02 326160-01 326161-01 903820-03 1001039-01 C 326114-01 C 950157-04 C 326131-01 C 326288-01 C 320974 C 251053-02 C 326189-01 C 904778-01 C64C PARTS LIST MAIN CASE ASSY Top Case, B3 Top Case, E Keyboard B3, E BOTTOM CASE ASSY Top Shield Assembly, B3 Top Shield Assembly, E Medal Angle, RT, B3 Paper Shield, E Shield Plate, Bottom E Bottom Case, B3, E Foot B3, E 250785-01 250785-02 326166-03 252114-01 251975-01 252113-01 252085-03 251976-01 252111-01 950150-03

C-64 BLOCK DIAGRAM CASSETTE PORT 1 MEG Hz«AO \—-V PADDLES RF MOD SYNC CHROMA LUMA 6510 MICRO SID CHIP V V MONITOR 6567 VIC CHIP 1 2 3 4- 5- 6- 7- ADDRESS DECODING PLA J DATA BUS ADDRESS BUS 6 EXPANSION PORT BASIC ROM 8K KERNAL ROM 8K CHARACTER GENERATOR ROM 4K 64K ROM USER PORT 6526 CIA KEYBOARD MATRIX CONTROL PORTS

C64 CIRCUIT THEORY u +5V +5V +SV R36 IK <ftESET > NC U Reset Logic Circuits. U20 is a 556 IC timer configured as a one shot multivibrator. The output pulse width is determined by the size of R34 and C24. Pulse width = 1.1 x R34 x C24 » .5 seconds. The output on pin 9 is "high" active. The output of U8 is "low" active. Reset initializes all the processor logic and causes the processor to load the program counter register with the address of the first instruction of the operating system program called the KERNAL. The starting address is stored in locations $FFFC and $FFFD. The first instruction is decoded and executed giving KERNAL control of the computer opera tions. The reset pulse occurs when turning the power on to the computer.

+Vc C64 CIRCUIT THEORY U32 MC4O44 8.1616 MHi The C64 Clock Circuits. X (N457I Crystal Y1 develops a 14.31818MHz fundamental frequency clock signal. U31 is a Dual Voltage Con trolled Oscillator. The output on pin 10 is a 14.31818 MHz clock signal called the color clock. R27 can be adjusted to obtain exact output frequency. U30 is a frequency divider that outputs a 2MHz signal on pin 6. U29 is a D flip flop which outputs a 1 MHz signal on pin 9. U32 is a Phase/Frequency Detector which compares the output of the U29 to the phase 0 clock, and outputs a dc voltage on pin 8 that is proportional to the phase difference between the inputs. The second half of the Dual Voltage Controlled Oscillator U31 generates an 8.1818MHz clock signal called the DOT Clock. The VIC IC divides the DOT clock by eight and outputs this as the phase 0 clock on pin 17. The output of the Phase/Frequency Detector is applied to the frequency control input pin 2 of U31. This causes tracking of the dot clock and the color clock because one input, pin 3 of U32, is the phase 0 clock which is derived from the dot clock, and the other input pin 1 of U32, is derived from the color clock. I t f TfiP o t-5 u I U3/ 87ol PAL OPEN T The C64B Clock Circuits. Refer to schematic 251469 Crystal Y1 develops the fundamental 16MHz clock signal. U31 is a Clock Generator IC that outputs the 8.1818MHz DOT clock on pin 6, and the 14.31818 MHz color clock on pin 8.

COMMODORE C64 C64C Service Repair Fix Manual

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