SJ-MD100 supplement - MiniDisc Community Page
Contents
1. e Thus to record the signals 1 0 1 1 0 1 0 the direction of the magnetism at the locations where 1 is to be recorded must be changed to face upward north south Because the magnetic film is strongly magnetic once a downward facing magnetism is recorded it is not easy to change it to an upward facing magnetism e By directing a laser beam at the magnetic film the temperature of the location that the laser beam strikes rises to the Curie temperature recordable MD about 180 C eliminating the magnetic force retention force Because the magnetic film is strongly magnetic similar to a permanent magnet once it is magnetized it has a strong retention force In order to eliminate that retention force it is irradiated with a laser beam so that the temperature rises to the Curie temperature e After the magnetism of the specific location is eliminated an external magnetic field with an upward direction north south is applied thus changing the direction of the magnetism at that location to face upward north south e Conversely if a downward facing south north external magnetic field is applied the direction of the magnetism at that location is changed to face downward south north e Then when the disc rotates and the location which has been changed to upward facing magnetism leaves the laser spot the temperature of the magnetic film drops and the upward facing magnetism recorded at that location is retained e In this way di2. I 2 6V 0V s there output from IC1 pin 29 TP148 or IC3 pin 87 4 NO Is voltage output from IC3 pin 96 NO YES Is RF signal stable Faulty IC3 YES rae Are communications between IC3 and IC72 OK NO YES Communications error Faulty C72 Does IC10 pin 13 change from H to L Faulty IC10 Faulty S4 ul 6 Continued on next page zts s playback possible Is playback sound OK NO YES Press eject key and remove ROM disc Can RAM disc NO be inserted Is UTOC read and disc data displayed Play track 1 of a previously recorded MD Is playback sound OK YES Insert a recordable MD Is recording possible NO YES Operation complete sJ MD100 SURV erat 16 9344MHz OVW 10 9344MHz Shan NO N 3 3V Is output of IC3 pins 61 65 OK during playback YES Faulty audio circuit Faulty IC3 5 To page 10 After TOC is read does traverse move to UTOC NO See Traverse Operation YES next page Faulty IC1 Is shape of magnetic head OK YES Faulty magnetic head Is there output from CN8 TP110 and TP111 NO NO YES Is output of IC3 pin 73 OK YES Faulty magnetic head circuit Faulty
3. MN66616 using EFM demodulation and ACIRC and the signals are stored in the DRAM IC72 MNV4400 At this time the cycle of the signals is adjusted by the LSI s clock in order to eliminate any jitter that might result from irregular revolution of the disc P4 The signals are sequentially taken from the DRAM IC72 and sent back to the MD LSI IC3 where they are ATRAC decoded and then output from pin 64 All of the above steps 1 through 4 are processed on the MD servo PCB and all of the signals are digital P5 The digital signals output from the MD LSI are input to pin 13 of the A D D A converter IC601 AK4520 via the interface IC 1C401 TC74HCT7007 input pin 3 output pin 4 where they are converted to analog signals and then output from pins 26 left channel and 27 right channel P6 The analog converted signals are output to LINE OUT via the buffer amp IC711 BA4560 input pins 5 left channel and 3 right channel output pins 7 left channel and 1 right channel At the same time they are also output to the headphone amp IC801 M5218 input pins 5 left channel and 3 right channel output pins 7 left channel and 1 right channel eThe MD servo PCB operates at Vcc 3 3 V and the main PCB operates at Vcc 5 V For that reason the exchange of signals between the two PCBs is performed via an interface IC during playback IC401 TC74HCT 7007 during recording 1C402 TC74HCT4050 eThe exchange of signals betw
4. 21 f Voltage alternates above and below VREF 1 65 V Faulty IC3 NO Faulty IC2 Does optical pickup move up and down y Continued on next page a4 Se Does CN4 pin 18 change from H to L when disc is inserted Faulty loading TRG S7 Is output of IC10 pins 13 15 17 and 18 OK NO Faulty S3 S4 S5 and S6 Is voltage of IC10 pins 8 and 9 OK YES Faulty IC10 Is voltage output from IC92 pins 2 and 4 Faulty IC92 Faulty loading motor IC3 pin 18 Voltage alternates above and below VREF 1 65 V Does output of IC3 pin 18 alternate above and below VREF 1 65 V Faulty IC3 Is voltage output between IC2 pins 13 and 14 Faulty IC2 Faulty optical pickup SJ MD100 Is TOC read and disc data displayed NO YES Is there output from IC1 pins 11 TP55 and 16 TP57 1 1 See Service Manual page 27 for measurements of IC1 Can waveform of IC1 pin 11 be adjusted so that it is approx symmetrical wih A level ol 4 Se Faulty IC1 or YES optical pickup Is RF Waveform output from NO IC1 pin 32 TP52 1 Is voltage YES output from IC1 NO pins 38 TP44 and 39 TP37 1 YES IC1 pin 29 TP148 or IC3 pin 87 Faulty IC1 Faulty optical pickup
5. 5 slightly approx 0 5 counterclockwise clockwise Subtraction amplifier detector 2 Semiconductor laser SJ MD100 Rewriting action of a magnet optic disc MD rewriting process e The signals recorded on an MD are rewritten using a new process called magnetic field modulation overwriting e In this process a laser beam spot of about 5 mW is focused on the location on the disc to be rewritten heating that location to the Curie temperature 180 C and thus canceling the magnetization e At the same time current flows to the optical pickup and to the magnetic head opposite it between the two of which the disc is held thus generating a magnetic field e When the disc revolves so the laser spot moves from the location to be rewritten the temperature drops below the Curie temperature and the magnetic field generated by the magnetic head re magnetizes that location e At this time if the direction of the current flowing to the magnetic head is reversed in accordance with whether the data being recorded is 1 or 0 the direction of the magnetic field also changes between north and south and accordingly the direction of the magnetization of the recording film changes between upward facing and downward facing Thus it is possible to directly magnetize the recording film on the disc in accordance with the 0 and 1 digital signals No need for a erasing head Thus the new recording data is overw
6. Is voltage of IC1 pin 36 2 6 V 1 NO Is voltage on both sides of R5 at least 0 025 V Is voltage of IC9 pin 3 2 6 V ue Faulty cg N Faulty IC1 3 3V YES ov Is there pin 92 1 See Service Manual page 27 for measurements of IC1 ls voltage of IC1 pin 2 left side of R8 approx 1 8 V Faulty IC1 Is voltage on both sides of R5 at least 0 V Faulty Q1 Faulty optical pickup Is current flowing equal to at least 1 2 times value indicated on pick FPC 2 Faulty optical pickup 2 Indicated value Current equal to that on both sides of R5 divided by 1 Q 3 3V oV NO Faulty IC3 Is output of IC3 pin 92 OK Is voltage of IC1 pin 2 left side of R8 approx 1 9 V 4 Faulty IC1 YES Faulty optical pickup Ps ee ROM RAM Operation Can ROM NO SJ MD100 disc be inserted correctly H 3 3V L 0V Does output of IC3 pin 21 alternate above and below VREE 1 65 V YES Is voltage output between IC2 pins 17 and 18 Faulty spindle motor 1C10 Dise mav TSTOPPLAY REC 43 LOAD OPEN SWO S3 L H H a LOAD PLAY SW S5 H HEL amp LOAD PLAY REC SW3 S6 H L H amp DISC IN en LiT IC3 pin
7. ORDER NO AD9903069S2 Service Manual KA SJ MD100 Ry Colour K 2 0 Black Type Areas Thi ment i lementar h EJ tse Europe E This document is supplementary to the EB Great Britain following Service Manual EG Germany Model No No AreaCode Code Order No No ee MD100 eee EG ee E Purpose Supplement for technical information about MD E Contents 1 Measuring instruments and special tools ROM Part No RFKV0006 Test Disc e ROM Part No RFKV0014 e Extension Cable Kit Part No RFKZJMD100EK Extension Cable Kit e Laser Power Meter Model No LE8010 Made by Laser Electric Laser Power Meter 2 Basic Knowledge of MD 3 Operating Procedures 4 Troubleshooting Guide for MD Servo Circuit Z WARNING This service information is designed for experienced repair technicians only and is not designed for use by the general public It does not contain warnings or cautions to advise non technical individuals of potential dangers in attempting to service a product Products powered by electricity should be serviced or repaired only by experienced professional technicians Any attempt to service or repair the product or products dealt with in this service information by anyone else could result in serious injury or death 1999 Matsushita Electric Industrial Co Ltd e Technics AlI rights reser
8. ding and playback blank guide grooves called pre grooves recordable MD are formed around the entire surface of the disc at the production stage e As shown in the illustration below the pre grooves wobble very slightly in a regular pattern and that curve is fine modulated at intervals of 13 3 ms to record beforehand the addresses of the continuous time data e Technically speaking the pre grooves in the disc is not perfect spiral but is wobble with a typical amplitude of 30 nm a spatial period of 54 to 64 um When this wobble is locked to a frequency of 22 05 kHz the velocity of the disc should be in the range of 1 2 to 1 4 m s e In this way even if the MD is blank because the addresses are already recorded around the entire circumference of the disc when the MD is recorded those addresses are read in order to control the movement of the optical pickup and perform CLV control e To record immediately quick access is first performed to quickly search for an blank area on the disc and then recording will automatically begin When recording is completed that address is automatically recorded in the U TOC user table of contents area so it can be read during playback for quick and easy access This also makes it easy to edit the track number User TOC area e Thus with an MD when the recording is completed the track data is automatically written in the U TOC area at the innermost part of the magnetooptic disc The data i
9. e specifically developed for MD The following is a description of the functions of those six LSls e This LSI controls the laser and performs the detection processing of the servo signals and of the audio signals from the disc needed to correct the position of the laser spot e This LSI receives the laser spot position correction signals from the RF amplifier and controls the focus servo that ensures that the laser spot is correctly focused on the disc surface and the tracking servo that controls the disc rotation direction to ensure that the pits on the disc surface are traced correctly e This LSI demodulates the address signals that are recorded in the pre group on a playback record magnetooptic disc MD In addition to reading the absolute addresses the address decoder also functions to control the rotation speed so that the servo signal is obtained at a constant linear speed at the location being read e This is the main signal processing LSI EFM is a circuit which converts 8 bit digital signals into the 14 bit format recorded on the disc It also performs signal processing for error correction changing the interleaving format in order to use the ideal algorithm for MD In addition this LSI also performs other tasks such as encoding during recording and decoding during playback e This memory controller provides a shock proof memory e This LSI performs the signal processing for the ATRAC compression technology that was specifically devel
10. een the DRAM and the MD LSI is performed using four data lines pins 1 2 24 and 25 of the DRAM and pins 43 44 45 and 46 of the MD LSI Record R1 The analog signals input from LINE IN pass through the REC LEVEL VR and are input to pins 5 left channel and 3 right channel of the A D D Aconverter IC601 via the buffer amp IC751 BA4560 input pins 5 left channel and 3 right channel output pins 7 left channel and 1 right channel R2 The analog signals input to the A D D A converter IC601 are converted to digital signals with a sampling frequency of fs 44 1 kHz and then output from pin 14 to pin 65 of the MD LSI IC3 via the interface IC IC402 TC74HCT4050 input pin 3 output pin 4 R3 The signals input from OPTICAL IN are input to pins 70 and 71 of the MD LSI IC3 via the interface IC IC401 input pin 9 output pin 8 R4 The signals input to pins 70 and 71 of the MD LSI IC3 are converted to a sampling frequency of fs 44 1 kHz by an fs converter inside the LSI If the signals are already fs 44 1 kHz they bypass the fs converter R5 The signals converted to fs 44 1 kHz or the signals input to pin 65 are ATRAC encoded and stored in the DRAM IC72 R6 The signals are sequentially taken from the DRAM IC72 and sent theback to the MD LSI IC3 where they are ACIRC processed and EFM modulated and then output from pin 73 to the magnetic head R7 The magnetic disc records the signals onto the disc by magne
11. encoder Using a maximum time of 11 6 ms as a single unit the encoder converts the digital waveforms within each single unit into about 500 different frequency spectra and then analyzes the strength level of each frequency Then as shown in the figures below utilizing the two principles of the threshold of audibility and the masking effect only the signals actually heard by the human ear are selected and compressed to one fifth the original volume eThis complex process is performed by an LSI chip called the ATRAC Threshold of audibility _ Signals below the threshol Sound lebel dB Audible rabge 2 Masking by high level sounds of audibility are eliminated Sound lebel dB Sound lebel dB 100 100 Threshold of audibility altered by signal A signal B becomes inaudible 80 Signal B can be heard but signal C cannot eo Threshold ot audibility Inaudible range 20 50 Fig A 100 200 500 1K 2K 5l Frequncy Hz Inaudible 10K 20K 10K 20K 20 50 10K 20K Frequncy Hz Fig B Frequncy Hz Fig C SJ MD100 Composition of an MD system Development of 6 LSIs RF amplifier Servo control circuit Address decoder EFM and ACIRC encoder decoder Anti vibration memory controller Audio signal compression encoder decoder New generation LSIs e The figure below shows the composition of an MD system An MD system uses six LSIs that wer
12. gital signals of 1 upward facing magnetism and 0 downward facing magnetism are recorded on the tracks on the disc Vertical magnetization With a conventional magnetic recording tape the magnetic material is magnetized parallel horizontal to the system surface of the tape A magnet optic disc however uses a vertical magnetization system in which the magnetic poles are recorded perpendicular vertical to the disc surface Because the magnetism is recorded vertically rather than horizontally much more data can be recorded in a smaller area Number of recordings possible e A magnet optic disc can be recorded more than 1 million times so it can virtually last forever Magnet optic disc recording principle D Laser spot Disk rotation direction Disk rotation i SABEN direction Only locations struck by a Assuming that the directions of powerful laser beam the magnetism on the unrecorded 4 4 4 4 4 4 Ey 4 u g 4 4 4 u 4 4 4 4 4 4 4 reach the Curie temperature disc are all facing downward Pe are eel a they may also all face upward ose r mag S retention force Laser spot Disk rotation direction Disk rotation Heated Recorded signals direction y An external magnetic ccoumowencare SOStItVSoogres Gm cocoot sysysas demagnetize locaton a 0 digital signal is recorded creating upword facing 00010100111001 N magnetism Upword 1 External magnetic field
13. is applied Downword 0 S Surface of the disk is a magnetic thin film made of terbium cobalt alloy C Horizontal magnetization D amp Vertical magnetization TATAA DES D SJ MD100 Playback of a recordable MD Playback of a recordable Because the signals on a magnet optic disc are recorded vertically as north south and south north magnetism the MD north and south magnetic poles appear on the surface of the disc s magnetic film These signals are played back utilizing a phenomenon called the Kerr effect which occurs when a weak laser beam strikes the magnetic poles e Light has wave vibration directions called planes of polarization Polarization refers to a light wave which vibrates only in a fixed direction e With normal light because the wave vibration directions are all mixed no planes of polarization appear e Because a laser beam is artificially generated light it is possible to align the planes of polarization e When a laser beam strikes something that has a magnetic field the direction of the plane of polarization of the reflected light varies very slightly in accordance with whether the magnetism is north polarity or south polarity When playing back a magnet optic disc MD these slight changes in the direction of the plane of polarization are read Reading of magnetic signals To further explain the principle used to read the signals recorded on a magnet optic disc first a la
14. magnetic head Faulty IC3 15 SJ MD100 Traverse Operation Traverse operation Remains at outer track Remains at inner track Is IC10 pin 12 approx 0 V Faulty shorted traverse detection switch S8 Is 1C10 pin 12 approx 3 3 V Faulty traverse detection switch S8 Is output of IC3 pin 20 OK Is voltage output between IC2 Faulty IC3 pins 15 and 16 Faulty traverse motor Faulty IC2 Printed in Japan F990406500MT KH D 16
15. oped for MD e New genaration LSIs developed for higher performance of MD system There are reduced to three LSIs 1 RF amplifire 2 4 ch driver servo control 3 Signal processor a Block Diagram for playback record MD circuit Cartridge Spindle motor 4Mbit DRAM Audio input gt EFM and ACIRC encoder decoder Audio output Servo control System controller circuit SJ MD100 Operating Procedures Play P1 To read the signals recorded on the disc the laser beam emitted by the laser diode LD strikes the disc and is reflected back and detected by the photodetector PD eFor a pre mastered disc similar to a CD the signals are recorded as pits on the surface of the disc and the signals are detected by the amount of light reflected when the laser beams strikes the pits eFor a recordable disc the signals are recorded by magnetizing the magnetic film on the surface of the disc and there is no variation in the amount of light that is reflected so the signals are detected using the shifting of the polarization of the reflected light due to the Kerr effect P2 The detected signals are input to pins 38 and 39 of the RF IC IC 1 where they are amplified and then output from pin 32 eBy observing the input signals between pins 38 and 39 and the output signals pin 32 on an oscilloscope it is possible to check the eye pattern P3 Error correction of the amplified signals is performed by the MD LSI IC3
16. oximately half that of a CD and the thickness is 1 2 mm the same as a CD Similar to a CD only one side of an MD disc is used to store data e The MD disc is made of polycarbonate the same material that is used for a CD Polycarbonate is a type of engineering plastic that is highly resistant to temperature and humidity as well as having excellent wear and impact resistant e A clamping plate is mounted in the center of the MD disc and when the MD is loaded into a player a magnet in the player attracts that metal plate to secure the disc in place If the MD disc were to be secured by clamping it from above and below similar to a CD it would be necessary to have a hole pass through the center of the MD cartridge which would reduce the amount of space available for attaching a label By using this magnetic method of securing the disc the entire front side of the MD cartridge can be used as a label area e Because of the metal plate mounted at the center of the MD disc the center of the cartridge is 2 mm thick slightly thicker than the rest of the cartridge e To protect the MD disc from dust fingerprints and other things that might hinder the reading of the recorded signals the disc is stored inside a cartridge similar to that of a floppy disc When the MD is loaded into a player the shutter on the cartridge is opened and the disc is ready to be played e For a recordable MD because there is no need for a recording head and it is only neces
17. r counterclockwise Those subtle differences in the reflected light are picked up by two light receiving elements and detected as either a 1 or a 0 by reading whether there is electrical current or no electrical current e If an MD were recorded in the same way as a CD it would only have about 15 minutes of recording time However by using a new signal compression technology called ATRAC that was specifically developed for MDs the signals are compressed to approximately one fifth making it possible to record for an extended time of 74 minutes the same as with a CD Blank MDs are currently marketed in two recording times 74 minutes and 60 minutes e Although MDs were originally developed for use in recording and playing back music in July 1993 the MD data standard was established By using an MD data music player MDs can be used as external memory storage media for computers and a single MD has a storage capacity of 140 MB equivalent to about 100 floppy discs e Construction of an MD Construction of an MD Materials used in an MD A 3 Construction of magnet optic disc Upper shell S Shutter window lt Clamping plate Bee Erasure a Shutter lock Lower shell Sager Shutter f Shutter window J e The playback only MD and the recordable MD are exactly identical in size and shape e The figure below is a cross sectional diagram of an MD disc The diameter of an MD disc is 6 4 cm appr
18. reproduction 4 Curie temperature The temperature at which magnetism of a specific material dissipates This temperature varies according to the material BUTOC eree User Table Of Contents Found only on recordable MiniDiscs this area contains subdata track number etc which can be rewritten by the user 10 SJ MD100 Mi Troubleshooting Guide for MD Servo Circuit Switch power ON with no MD loaded Does player enter self check mode 1 NO CN4 5v 5V 0 3 3V sv l s Is CN4 power supply line OK See Srevice Manual page 35 Set to read power adjustment mode 2 Check power supply circuit on main unit See Srevice Manual page 69 Is oscillation signal output from IC10 pin 33 Is read power output 10 02MHz YES IC10 pin 33 Continued on next page Can read power be set to 600uW or lower using VR1 Set to write power f adjustment mode 3 Faulty optical pickup 3 See Srevice Manual page 69 NO Is CN4 pin 14 H Is write power output 2 Continued on next page Adjust write power and check ROM data laser Faulty IC10 power and RAM data laser power Check reset circuit on main unit To ROM RAM Operation page sits SJ MD100 Is output voltage of IC1 pin 37 TP35 approx 1 3 V 1
19. ritten regardless of the direction of the previously recorded magnetization eliminating the need for an erasing head e This process is called magnetic field modulation overwriting e Because this magnetic field modulation overwriting makes it possible to directly overwrite the new signals on top of the old signals in a single process re recording on a MD is just as easy as with a magnetic tape making the MD ideally suited for use in personal audio equipment Magnetic field modulation overwriting Head drive signal Recording head Generates a magnetic field Vertical recording lt Recording magnetic field orecoingtack Bele e belele New recording signal ee Old signal 5 Die rotation Laser beam New recording signal Old signal recoraingtrack Nisia s Ksjnjs n fs New signal Overwrite means to write new data while erasing the old data SJ MD100 Random access on a recordable MD Random access on a With a disc high speed random access is possible something which is not possible with a tape playback only MD e The optical pickup moves quickly in the radial direction thus directly accessing the start of each track e With an optical disc which is capable of playback only the addresses in the TOC table of contents in the lead in area are all read beforehand in order to access the start of each track Random access on a With a recordable MD which is capable of both recor
20. s then read during playback for quick and easy access e The addresses for the start locations of each track track mark and also the addresses for the end locations are all recorded in the U TOC so when editing a track all that has to be rewritten is the area address e This is similar to the directory that a computer writes on a floppy disk Pre grooves on a magnet optic disc gt Pre grooves Laser spot Control the tracking of the Wobble in a optical pickup regular pattern On a blank MD the address are already recorded around the entire circumference of the disc When the MD is recorded the address are read in order to apply spindle servo control 4 and to perform CLV control Disc substrate Laser beam Spindle servo control means control of the disc s rotation speed SJ MD100 ATRAC signal compression technology What does the word ATRAC mean Why is signal compression necessary Basic concept of ATRAC e ATRAC adaptive transform acoustic coding is the name given to the signal compression technology that is one of the most important technologies used in the MD system The principles of this technology are extremely complex so here we will only explain the basic concept e Simply speaking utilizing the characteristics of the human auditory sense the sounds that cannot be heard by the human ear are eliminated so that only the sounds that can be heard remain thus reducing
21. sary for a laser beam to be directed at the underside of the disc the shutter is located only on the back of the cartridge e For a playback record magnet optic disc MD because it is necessary for the recording head and the laser beam to be able to access both sides of the disc the shutter is located on both sides upper shell and lower shell of the cartridge Recording of the music signals begins here Infomation describing the contents and advances outward of the music signals such as the number of tracks the playing time etc is recorded here Disc diameter 64mm Lead out area Radius 16mm 32mm Radius 14 5mm i ii vi ENE i Inner Outer tracks tracks Polycarbonate Clamping plate Dn aa Hole diameter i 11mm SJ MD100 Recording on a magnet optic disc Can be recorded and played By using a magnet optic disc digital signals can be recorded and played back over and over again back repeatedly Recording principle e To record on a magnet optic disc a laser beams momentarily heats pin spots on the magnetic film on the back of the disc and a magnetic field is applied from the other side of the disc Thus both sides of the disc must be accessed in order to record e To explain the recording principle we will assume that the directions of the magnetism on an unrecorded disc are all facing downward south north 0000 Actually on an unrecorded disc the directions are random
22. ser beam is directed at the disc If the direction of the magnetism recorded on the disc is upward north polarity the plane of polarization of the light reflected from the disc rotates very slightly clockwise as a result of the Kerr effect Conversely if the direction of the magnetism is downward south polarity the plane of polarization rotates very slightly counterclockwise e When the reflected laser light is passed through a Wollaston prism the light is distributed to photo detector 1 if the direction of rotation is clockwise or to photo detector 2 if the direction of rotation is counterclockwise e The light striking the two light receiving elements is converted into electrical current and a subtraction is performed If the result of A B is plus a 1 is detected and if the result of A B is minus a 0 is detected e An MD player is compatible with both optical recording and magnetic recording changing the reading system in accordance with the type of disc that is loaded Changes in the polarization axis g Playback of recordable MD gt due to the Kerr effect Magnet optic disc al alals Polarization axis 7 4 7 t Disc rotation direction lt lt Magnetic film Objective lens Half mirror Detection lens Photo rae detector 1 Addition amplifier South polarity North polarity A magbetism 0 magbetism 0 RF signal For amagnet Rotates very Rotates very optic disc slightly approx 0
23. the amount of data that must be recorded This principle is similar to the PASC signal compression that is used for digital compact discs e The amount of data that can be recorded per second the bit rate is 16 bits x 44 100 x 2 channels 1 411 200 bits per second or approximately 1 4 megabits per second 1 megabit 1 000 kilobits 1 million bits e However because the diameter of an MD is only about one half that of a CD it only has a capacity of about 160 megabytes In order to record the same 74 minutes of data as a CD the bit rate of 1 4 megabits per second must be compressed to one fifth ATRAC is the signal compression technology that was developed in order to do that Signal compression is rather like the technology for orange juice concentrate in which the best part of the fresh orange is concentrated for easy transportation and then reconstituted with water before drinking e The basic concept of ATRAC utilizes the characteristics of the human auditory sense The frequency spectrum that cannot be heard by the human ear Fig B and the frequency spectrum that cannot be heard because it is masked by high level sounds Fig C are cut and the bit rate is compressed by appropriately arranging the bits thus making it possible to fit all of the necessary data within the capacity of the disc eTechnically speaking the analog signals are converted to 44 1 kHz 16 bit digital signals and these signals are then processed by the ATRAC
24. tizing the magnetic film on the surface of the disc During recording the laser diode emits its laser beam in order to raise the temperature to the Curie temperature that is required to magnetize the magnetic film For this reason the optical power of the laser diode is higher during recording than during playback eAlthough the disc revolves at a speed fast enough to write the signals without compression the recording signals are compressed in order to reduce the data volume As a result the signals are written intermittently rather than continuously the recording signals are intermittently sent to the magnetic head Control C1 Performs the necessary controls for each operation during playback and recording and for writing of the UTOC at the end of recording eThe information written in the UTOC includes the recorded track numbers and their addresses text data etc C2 Performs the necessary displays of the text data recorded on the disc and for each operation The system is designed for integrated operation so that the system control IC IC10 on the MD servo PCB and the system control IC IC901 for the component system mutually exchange data communicating Clock eThe controls of the playback signal recording signals and of the 4 channel driver IC IC1 AN8772 all function using the clock on the MD LSI as the master clock eThe A D D A converter IC601 functions by using the clock signal of the MD LSI as the master clock and frequenc
25. ved Unauthorized copying and distribution is a violation of law SJ MD100 E Basic Knowledge of MD e Definition of an MD and the types of MDs What is an MD Two types of MDs Playback only MD is same as a CD Recordable MD uses magnet optic recording Playback of a Recordable MD 74 minute recording time Can also be used ona computer e MD stands for mini disc e Similar to a music CD an MD is also a small disc capable of recording and playing back digital sound e There are 2 types of MDs a optical disc for playback only MD and a magnet optic disc for recordable MD that is capable of both recording and playback e A playback only MD is merely a smaller diameter version of a CD Just like a CD the signals are read by light striking pits on the surface of the disc e With a magnet optic disc MD Recordable MD that is capable of both recording and playback recording is per formed by a vertical magnetization system in which a magnetic thin film on the surface of the disc is heated by a laser beam and magnetism is applied in accordance with the data audio signal being recorded e When a recordable MD is played back a laser beam weaker than that used during recording strikes the disc and is reflected back and the reflected light is twisted polarized in accordance with whether the magnetized direction is upward or downward causing the reflected light to rotate very slightly clockwise o
26. y sampling that signal 384 times via the clock generator IC501 TC9246 SJ MD100 Block Diagram DRAM 4Mbit IC72 MNV4400 Magnetic Magnetic head OO8 head Drive Q10 11 Clock 16 9334MHz 6 0 9V 0 45V P P P P 0 5us 0 1V DIV MDLSI 0 5us 50mV DIV IC3 MN66616 EFM mod demo Traverse Spindle ATRAC encoder motor motor decoder Servo signal processor Loading Motor See System control IC10 Detection SW MN101D03D M Clock 10 02MHz FL display Ke System control Interface IC901 i TC74HC4 M30218 Operation SW Interface IC401 TC74HTC7007 generator IC501 TC9246 20bit AD DA converter Buffer AMP IC601 AK4520 IC751 BA4560 1kHz 0dB 1kHz 0dB Buffer AMP Head Phone AMP IC801 M5218 IC711 BA4560 ye 1kHz 0dB Play signal C REC signal SS SS Clock line VOLUME CENTER Control line 1 Kerr effect A phenomenon in which the polarization plane of laser light reflected from a material shifts in one of two directions depending upon its plus or minus magnetic polarization 2 ACIRC Add on interleave CIRC The aim of Add on interleave is to improve the resistivity in CD ROM decoder from the burst error on the disc 3 ATRAC 7 Adaptive Transform Acoustic Cording The digital data compressing system developed for MiniDisc in which audio signals can be reproduced with only about 1 5 in the data normally required for high fidelity
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