SERVICE MANUAL MODEL C64 COMPUTER
Contents
1. 2 V SELECT BOARD LAYOUT 7250425 01 28 MODULATOR SCHEMATIC 251696 T LOP ite Ail 20 5410 a F 83 92 22 LOC HET ns NOTES OZ MAIShK o EQUIVALENT 23 4437 GR EQUIVALENT EQUIVALENT 0 7 5 2 OS 4 26 AAS AR EQUIVALENT 27 02 220224034 EQUIVALENT GJ Q4 ZSC 2778 28 EQUIVALENT as 2 GR EQUIVALENT COMPONENT PARTS VALUE Ran CQ2. 00150201 7 R6 Ui 50 906114 01 R23 RG Bo Wis lesisiD c906112 01 R 19 6567 C 906109 04 u20 901523 03 021 1724 4161 20015 901505 01 The input video line requires a 470 ohm 1 4 watt resistor soldered to ground M 26 741533 00152109 27 174138 901521 03 028 4066 901502 01 29 7414 01521 06 U30 74148193 90152126 CAPACITORS 7405609 901521 68 52 4044 06128 01 47uF 50V 20 Cs Electrolytic 10 uF 25V 50 10 TRANSISTORS 47uF 50V 20 0000 00265201 10 Ceramc Q2 N3904 902658 01 CI2 15 Electrolytic 10 uF 25V 50 10 3 902653 01 C16 Ceramic SOV 48 Dw2222 90268601 Electrolytic 10 uF 25V 50 10 jlur sov DIODES C19 Electrolyte ss 2200uF 16V0 27 Zener IN4371 20 21 22uF 100V 20 00000 ICR2 SVZemrINTSS 2 Ceramic RP1 33 8 Pin Bourne No 430BR 102 330 RP3 RP4 33K 8 Pin Bourne No 430BR 101 332 3 3K 10 Pin 5 Iko U25 74L8257 901521 57 RESISTOR PACKS ICR56 Rectifier N4001 25 28 Ceramic 224 509 RESISTORS values ohms 1 4W 30 31 32
3. 1 zeae mH 8 E mim 3 CHT 2 2 5 CO4 Ce La E 27 257 soy 20 20 LE 2 2 aH CAM S Coe I 5 AF 20 The Power Supply The external power supply generates a regulated 5 and 9VAC 5VDC is applied to pins 5 and 1 of CN7 on the C64 pcb Filtered by L5 C97 and C100 it is then controlled by on off switch S1 This 5SVDC output supplies the microprocessor logic 9V AC is applied to pins 6 and 7 of CN7 on the C64 pcb 12VDC 5 CAN and 9VAC unregulated are outputs that are derived from this 9VAC supply The 9VAC supply is made available on pins 10 and 11 of the USER PORT CN2 12VDC Generation 9V AC is added to 9VDC through CR6 and rectified by CR5 The unregulated DC output is filtered by C88 and C89 then regulated at 12VDC by The regulated output is filtered by C57 and C59 The 12VDC supplies the VIC and SID IC and the audio amplifiers 5VDC CAN Generation 9VAC is rectified by CR4 The unregulated DC output is filtered by C19 and C95 then regulated at SVDC by VR2 The regulated output is filtered by C102 and C103 The output called SVDC CAN is separated and individually filtered into two outputs called Vvid and Vc Vvid is the 5VDC supply for video circuits and is the SVDC supply for the clock circuits 9VDC U
4. Check U7 6510 MPU Cassette motor keeps running even after a program is done loading The TIP 29 Check Cassette Port for Shorts transistor gets extremely hot and the fuse may possibly blow R4 Possibly Open The cursor disappears when the cassette is plugged in Check U7 6510 MPU Cassette runs extremely slow The program seems to load but will not run Check U7 6510 MPU SYMPTOM POSSIBLE SOLUTION When loading from cassette the SYNTAX ERROR message is displayed Check U20 556 IC DEVICE NOT PRESENT ERROR is displayed when disk is used Check U1 6526 CIA U7 6510 MPU R28 R29 R30 Disk drives continue to search when trying to load Check U2 6526 CIA When loading from disk and any key of the 4th row of the keyboard is pressed U20 556 IC the cursor goes to home position R35 Possible Bad Connection When loading from disk a FILE NOT FOUND message is displayed Check U4 ROM U2 6526 CIA OUT OF MEMORY is displayed when disk is used Check U20 556 IC VERSION Original A CR B 2 C64 BOARD IDENTIFICATION To date there are 4 version of 64 PCB assemblies in use IDENTIFYING FACTORS 5 pin board CN5 Video port has 5 pins 8 pin board CN5 Video port has 5 pins 8 pin board Reduced oscillator circuit 8 pin board 326298 01 250407 04 250425 250441 01 SCHEMATIC 326106 251138 251469 251469 These boards are interchangeable with casework key
5. DD00 DDOF I O1 DE00 SDEFF 02 8105 00 ROM Address Decoding Basic ROM resides at locations A000 BFFF The output F1 pin 17 of the PLA 17 goes low when the BASIC ROM is selected The KERNAL ROM resides at locations E000 FFFF The output F2 pin 16 of the PLA UI7 goes low when the KERNAL ROM is selected The CHARACTER GENERATOR ROM resides at locations 0000 DFFF The output pin 15 of the PLA UI7 goes low when the Character Generator ROM is selected The Expansion Port Connections The expansion port is an extension of the microprocessor address data and control bus ROML decodes addresses 8000 9FFF and decodes addresses E000 SFFFF These are outputs from the PLA used to select the catridge inserted in the expansion port I O 1 input from 715 decodes addresses DE00 DEFF 2 output from U15 decodes addresses DF00 C64 CIRCUIT THEORY RAM Control Logic 013 925 are multiplexers The address output from the microprocessor are passed to RAM via U13 U25 when the output Address Enable Control AEC from the VIC IC is high When AEC is low the VIC IC outputs refresh addresses on pins 24 31 AEC goes low when the system clock phase 2 is low Since all decoding occurs when phase 2 is high refresh is transparent to the processor Eight 4164 DRAMS provide 64k bytes of memory One 2114 RAM U6 provides 512 bytes of memory allocated for sc
6. Se EXE Hes ER abe T n Iu Tne ae T E 1 mr Keyboard Joystick and Paddle Interface Circuits Keyboard Interface U1 is a Complex Interface Adapter CIA Both parallel ports are used to decode the keyswitches on the keyboard Parallel port A signals PA7 are outputs PArallel port B signals PB7 are inputs A 0 bin is shifted through the parallel port A when a key is depressed on the keyboard the 0 bit is returned on one of the parallel port B inputs A program in the KERNAL ROM generates the shifting 0 bit output on parallel port A and decodes the signals returning on the parallel port B inputs Depressing the restore key causes U20 to trigger U9 pin 6 goes low generating a Non Maskable Interrupt NMI at the processor This causes the processor to execute a subroutine which initializes the I O interfaces If the STOP key is depressed at the same time BASIC flags are initialized ee b 112 E510 Ew KEYBOARD MATRIX Joystick Interface UI also controls the joystick Parallel port A accepts inputs from the B joystick connected to control port 2 Parallel port B accepts inputs from the A joystick connected to control port 1 When the joystick is moved up down left right or the fire button is depressed a ground potential is applied to the appropriate
7. input of U1 Paddle Interface A Variable resistor is connected to adjusting knob on the paddle When the knob is rotated the resistance varies controlling the time constant of an RC network The Voltage developed across the capacitor is input to an A D converter internal to the SID chip U18 The digital output is stored in one of the SID registers The paddle position can be determined by the reading the contents of the appropriate register U28 is a 4066 CMOS switch The signals from the paddles are passed to the SID chip when the Enable inputs EO E3 of U28 are high NOTE 01 port assignments are incorrect on schematics Refer to Keyboard Matrix for correct assignments C64 CIRCUIT THEORY td a a 3 io T i a LL E H Le Rn am TM n XT 3E us a 1 li HE Lam pls un Serial Interface and User Port Circuits The Serial Interface U2 is a Complex Interface Adapter CIA Parallel port signals PA3 PA7 control the serial bus interface is the Attention ATN output This signal is inverted by U8 before being transmitted to a device on the bus PA4 is the clock output Data transmitted from the C64 to a device on the bus is synchronized by this clock signal U8 inverts the output PA4 PAS is the data output U8 inverts this
8. 6510 MPU U20 556 IC When RETURN is pressed after a run command the cursor goes back Check U3 ROM to home position Poke command does not work Check U3 ROM Joystick does not operate correctly Check U1 U28 6526 CIA Wrong frequency Check C70 No character lettering is displayed on the screen Check U3 ROM U2 CIA Graphic characters instead of letters displayed Check U19 VIC II Power up message appears but no cursor Check U1 U15 U7 and U4 POSSIBLE SOLUTION Cursor jumps to back to home position Check U7 6510 MPU Abnormal colors appear in the letters Check U6 2114 RAM U16 4066 IC Different characters are displayed and cursor is locked when turned on and off Check RAM System does not reset and the RESTORE key does not work Check U20 556 IC White band scrolls down the screen 60 HZ HUM Check External Power Supply VR2 5V Regulator Cursor disappears after the system warms up Check U1 6526 CIA SYNTAX ERROR displayed after system warms up Check RAM U3 ROM Wavy screen after the system warms up Check External power supply U31 74LS629 U30 74LS193 The system resets when it warms up Check U7 6510 MPU U3 ROM Keyboard does not operate correctly when the system warms up Check U1 6526 CIA U3 ROM Black band scrolls through screen when the system warms up Check External Power Supply C90 C88 4 VR2 5V Regulator Cassette motor keeps running
9. Ceramic 1 uF 50V 5 unless noted 683 Ceramic uL PARTS LIST PCB ASSEMBLY 326298 Continued C Indicates mm Stocked Part Numbers CAPACITORS Continued CAPACITORS Continued 0 Ceramic 81 uF 50V Electrolytic ts 0 Ceramic 470 pF 50V C102 Blectrolytic x Er Ceramic 1 uF 50V Header Assy 20 Pin 90333 1 20 Ceramic 1 uF 50V 6 Pin Din 903361 01 es Ceramic 1 uF 50V 66 44 Pin Card Edge C 906100 02 Ceramic 22 uF 50V CN7 7PinDin C 906130 01 C60 61 Ceramic 47 uF 50 20 lc CN8 9 Plug Assy 8 Pin Rt Angle C 906126 01 062 Electrolytic 10 uF 25V 55096 10 0 Header Assy 3Pin c63 Ceramic 47 uF sov 20 64 69 Electrolytic 10 uF 25 50 10 MISCELLANEOUS C66 67 Ceramic 47 uF 50V 20 LL2 Coil Inductor 2 2 uH 901151 17 LNOAYI AMAT XI rr Fk z RFES 421 rer fee Te dash 2 cag Ec nean F MODULATOR SCHEMATIC 251025 HM g 101 03 JAJ sr 000 112 AETA if rese 8 4 26 i et h 1 ET 7
10. IDEO AND AUDIO OUTPUTS o 8 PIN VIDEO AND AUDIO OUTPUTS o CASSETTE INTERFACE o KEYBOARD JOYSTICK amp PADDLE INTERFACES o SERIAL INTERFACE USER PORT e TROUBLESHOOTING GUIDE e BOARD IDENTIFICATION e ASSEMBLY 326298 01 BOARD LAYOUT PARTS LISTS o SCHEMATIC 326106 PCB ASSEMBLY 260407 04 o BOARD LAYOUT PARTS LIST MODULATOR SCHEMATIC 251025 o SCHEMATIC 251138 e PCB ASSEMBLY 250425 01 BOARD LAYOUT PARTS LIST o MODULATOR SCHEMATIC 251696 o SCHEMATIC 251469 o PIN ASSIGNMENTS 64 GENERAL DESCRIPTION MEMORY ROM MICROPROCESSOR DISPLAY COLORS CHARACTERS DISPLAY MODES RESOLUTION SPRITES SOUND KEYBOARD KEYS INPUTS OUTPUTS FEATURES PERIPHERALS COMPUTER The All Purpose Commodore 64 us 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 amp 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 o
11. SERVICE MANUAL MODEL C64 COMPUTER SEPTEMBER 1985 PN 314001 02 Commodore Business Machines Inc 1200 Wilson Drive West Chester Pennsylvania 19380 U S A Commodore makes no expressed or implied warranties with regard to the information contained herein The information is made available solely on as is basis and the entire risk as to quality and accuracy is within 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 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 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 Converted to PDF peter sieg1 gmx de in Jan 2007 CONTENTS e SPECIFICATIONS e PRODUCT PARTS LIST e BLOCK DIAGRAM e CIRCUIT THEORY o POWER SUPPLY o RESET LOGIC o CLOCK CIRCUITS EXPANSION LOGIC CONTROL LOGIC 5 PIN V
12. board etc however care must be taken to provide the customer with a unit that is compatible with their monitor and cable When component level repairs are necessary be certain to acquire the appropriate part for the board you are repairing Most modulators are different as are many of the components The 4th version of 64 board was recently developed and only a few may be in the field It is termed the 64B 2 All circuits remain the same as the 64B Schematic 251469 with a few component location changes 1 Resistors 28 29 30 36 48 were reduced to Resistor Pack 2 Diodes CR100 105 are no longer piggybacked Their new locations are CR9 12 16 8 ponam ne f TE LLLA LLL c cx BOARD LAYOUT 296998 01 PARTS LIST PCB ASSEMBLY 6 C Indicates Commodore Stocked Part Numbers INTEGRATED CIRCUITS RESISTORS continued ULU2 626 90608 180 fk D364BasicROM c90122 01 Rie R9 ROM 6901227 03 R7 hax R8 Us D364CharROM 90122501 9 We 2114L 30RAM 01453 01 07 j si0uProesor 906107 01 B1 7 Us 740 190152206 R2 sk K 0942 1640 R3 R s BD jus pasz 01521457 Ra IM 4 7418258 90152158 R2 RG lus 48 ps uie 406
13. ed cross references for TTL chips Transistors etc will be available in manual form through the Service Department in November of 1984 Unique or non standard part will be stocked by Commodore and are indicated on the parts list by a C TOP CASE ASSY Top Case C 326113 01 Keyboard C 326166 02 LED Plate C 326160 01 Nameplate C 326161 01 Lamp Hold Set C 903820 03 LED Assembly C 1001039 01 BOTTOM CASE ASSY Bottom Case C 326114 01 Foot Self Adhesive C 950157 04 PCB Shield Plate C 326131 01 PCB Insulation Sheet C 326288 01 ACCESSORIES Users Manual C 320974 Power Supply C 251053 02 RF Cable C 326189 01 Switch Box C 904778 01 64 BLOCK DIAGRAM 1 MEG 3 CASSETTE 5 PLA d POHT 7 MICRO DATA BUS PADDLES ADDRESS BUS MOD SYNC KERNAL CHROMA LUMA 8 j CHIP 3 MONITOR j ROM 6520 5526 j E CIA E CONTROL PORTS PORT y C64 CIRCUIT THEORY There are three versions of the C64 The C64 with five pin connector video output 326106 The C64 with an eight pin connector video output 251138 and the C64B which has improved system clock circuit design 251469 Most circuit theory explanations will be the same for all three versions Refer to schematic 326106 unless noted otherwise E E mr i PTT Lm m m aL a pe 2 ceu t E T A
14. f 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 Disk drive C1530 Datasette MPS 801 Dot matrix printer POWER REQUIREMENTS MPS 802 Dot matrix printer MPS 803 Dot matrix printer DPS 1101 Daisey wheel printer C1520 Plotter Printer C1702 Color monitor CM141 Color monitor 120 Volts 60 Hz Specifications subject to change without notice PARTS LIST C 64 PLEASE NOTE Commodore part numbers are printed for reference only and do not indicate the availability of parts from Commodore Industry standard parts Resistors Capacitors Connectors should be secured locally Approv
15. nregulated Generation CR4 rectifies the 9VAC input The output is 9VDC unregulated This supply powers the cassette motor transistor amplifier circuits and the RF modulator on the C64B version C64 CIRCUIT THEORY Reset Logic Circuits U20 is a 556 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 decode and executed giving KERNAL control of the computer operations The reset pulse occurs when turning the power on to the computer C64 CIRCUIT THEORY The C64 Clock Circuits Crystal Y1 develops a 14 31818MHz fundamental frequency clock signal U31 is a Dual Voltage Controlled 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 IMHz 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 pha
16. output also Data transmitted from a device on the bus to the C64 is synchronized by a clock generated by the transmitting device The Clock signal is input on Data transmitted from a device on the bus to the C64 is input on PA7 When a device the bus wants to communicate with the C64 SQR IN goes low indicating service is requested The User Port Parallel port B of U2 PBO PB7 is made available on the user port Parallel data transfers with external device are made very easily through this parallel port SP2 and SP1 are bi directional serial ports CNT 1 and CNT2 are bi directional synchronizing clock signals for each serial bus 64 TROUBLESHOOTING GUIDE SYMPTOM POSSIBLE SOLUTION Blank screen on power up Check External Power Supply U4 KERNAL ROM 917 PLA U7 6510 MPU U3 ROM U8 7406 IC U19 VIC ID U9 U12 4164 RAM U21 U24 4164 RAM 2 CR4 1 Out of memory error on power up Check U9 U12 4164 RAM U21 U24 4164 RAM USE DIAGNOSTIC TEST DISK No cursor displayed Intermittent blank screen Check 01 015 U7 Check U2 U7 Powers up with graphics display and blinking cursor Check U14 74LS258 IC Powers up with all the characters displayed as blocks Check U26 74LS373 IC Intermittent display Check C88 Possible Bad Connection Powers up with the PRESS PLAY ON TAPE message and the display Check U7 6510 MPU blanks Possible Bad Connection On power up the cursor lock up Check U7
17. reen color data storage C64 CIRCUIT THEORY 5 Pin Video and Audio Output Circuits Pin 15 of the VIC IC is the sync luminance output Pin 14 is the color output A composite video output is created by mixing sync luminance and color The composite output is applied to the RF modulator and also passed to the monitor connector CNS on pin 4 The color output is not made available on the monitor connector CNS as on the 8 pin version and the RF modulator mixes audio with the composite video producing the TV RF output unlike the 8 pin version RF modulator which creates the composite video output C64 CIRCUIT THEORY gil if 1 ra tion e t himm nm 2 1 BRN FEMALE OME iz 5 1551 B Pin and Audin Quod tn FE Gan 8 Pin Video and Audio Output Circuits Refer to schematic 21469 U19 is the Video Interface Chip VIC Sync horizontal and vertical and luminance video is output on pin 15 This signal is passed to pin 2 of the RF modulator Color is output on pin 14 and passed to pin 3 of the modulator Light pen inputs are sensed by the VIC IC on pin 9 U18 is the Sound Interface Device SID The audio output is on pin 27 and audio input is on pin 26 The RF modulator mixes sync luminance color and audio out generating a TV compo
18. se difference between the inputs The second half of the Dual Voltage Controller 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 1s 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 4 of U32 is the phase 0 clock which is derived from the dot clock and the other pin 1 of U32 is derived from the color clock r C64B Clock Circuits Refer to schematic 251469 Crystal Y1 develops the fundamental 16Mhz clock signal U31 is Clock Generator that outputs the 8 1818MHz DOT clock on pin 6 and the 14 31818 MHz color clock on pin 8 C64 CIRCUIT THEORY LL n a qim m 9 117 1 pa 1 2 Irt 4 et aci cup BT EIER i b EOE cu Ta E ett jH Pi 1 0 ROM Address Decoding and Expansion Port I O Address Decoding Logic U17 is a Programmable logic array PLA The output F5 on pin 12 called 1 0 goes low when any of the I O devices controlled by U15 are selected The addresses are listed below for each device VICIC 0000 D02E SID IC D400 D7FF Color Ram 0800 CIA 1 DC00 SDCOF CIA 2
19. site signal on pin 5 The RF modulator also passes the VIC outputs to the monitor connector CN5 Audio out on pin 27 is amplified by Q2 and output on pin 3 of CN5 Audio in is applied to pin 5 of CNS then to pin 26 of the SID IC Inputs from paddles connected to on of the control ports are monitored by the SID IC on pins 23 and 24 C64 CIRCUIT THEORY FY ums 1 38 Tir EET Te ha Cassette Interface Circuits U7 is a 6510 microprocessor One of the features of the 6510 is a built in parallel I O port PO P5 5 control most of the cassette interface circuitry P3 pin p6 of U7 outputs the write data signal to connector CN3 on pins E and 5 P4 is an input that senses the play switch depressed on the cassette deck P5 is on output that controls the cassette motor When P5 goes low Q2 cuts off CR2 regulates Vb of Q1 at 7 5 volts this forward biases Q1 and passing current through the cassette motor coil 1 is a Complex Interface Adapter CIA Parallel ports serial outputs and Timers are standard features of the CIA Read data enters on pins D 4 of CN3 UI accepts the read data signal on the FLAG input pin 24 C64 CIRCUIT THEORY Mr Rr 2 2 EFLFE aL H T peel cit NN 5 Ge OBE
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