Seagate ST425 Service Manual 1984
Contents
1. 30 4 2 Exploded View 31 4 3 Component 32 4 4 Parts List 33 34 29 el FIGURE 3 6 INTERFACE CONNECTORS coven SCREW 96 32 x 1 4 g CAT Mo TORK SORE 6 32 SCREW PAN HD SLT TORX DR 7 CLAMP 553 WASHER gt D Leg PANEL MOUNT SPACER V GROMMET PANEL ISOLAT R VIBRATION SCREW x 1 4 SCREW 62 56 x 178 27 BUT Hb SLT TORK DR SCREW 4632 x 778 UT Hb TORK DR BUT HD TORK TT assy 2 EV ANTI TORQUE PLATE PRELOAD FLA ST ASSY BAND Go WASHER 1 REW 12 56 x 3 16 RAT TORA OR irs STOP THERMAL Qy SCREW 24 40 x 3 6 PAN SLT TORK OR ae x Assy FLTER gt ASSY STRAP or soar 25 MENS SS SPRING PIN TENSIONER BRACKET 4 SSY CARRIAGE SCREW 86 32 x 1 41 WAGE BUT HD TORK SCREW x 1 8 RETAINER REAR ROD BUT HD TORK OR BUT TORX OR ub P SCREW 6 32 x 3 16 BUT HD TORX DR scnew gt MACHINING BUT TORX OR CORD SS SCREW 6 32 x 5 16 BASE cats BUT Ho SCREW 6 32 x 3 16 42. 5 5 545 5 5 4 24 215 2 3 5 Write Operationssssssss sasiesese 1617 2 3 6 Fault Detection 18 2 4 Test Point Data PC Board 20321 001 19 21 2 5 Schematics 22 3 9 FIELD SERVICE AND 205 5 25 32 3 1 Removals and Adjustments 26 3 1 1 3 1 2 3 1 3 3 1 4 3 1 5 3 1 6 3 1 7 Main Control 26 Index Sensor 26 Ground Springs Front Cover M7 Front Cover LED 27 4 224 Track 0 2284 4 0 ILLUSTRATED PARTS CATALOG INDEX 29 4 1 Interface Connectors 30 4 2 Exploded View 31 4 3 Component Locations 32 4 4 Parts List PC Board 20321 001 33 34 5 9 FIELD SALES OFFICES 35 11 ILLUSTRATIONS FIGURE PAGE 1 0 Test Point Layout PC Board 20321 001 20 2 0 Test Point Timing PC Board 20321 001 21 3 8 Interface 3 4 0 Exploded 0 5 0 Component Locations Board 20321 001 34 1 9 INTRODU
3. 22 2 Hz 040 double amplitude DC Power Requirements 12 Volts 5 1 5 Volts 5 1 Maximum Ripple 5 6 3 5 at power on 1 1 7 6 to 12 5 Heat Dissipation Typical 25 Watts Maximum 29 Watts Mechanical Dimensions Height 3 26 inches Maximum Width 5 75 inches Depth 8 00 inches Weight 4 6 pounds 2 1 Kg Shipping Weight 7 9 pounds 3 2 Kg 1 1 2 Reliability Specifications 11 000 8250 usage 30 minutes Not required The component design life is 5 years Read error Soft Hard Seek Bit jitter Rates Based on bit jitter reduction Read Errors 1 per 1919 bits read Read Errors 1 per 1912 bits read Errors 1 per 196 seeks reduction determines the relationship between the leading edge of read data and the center of the data window The data separator must provide at least 49 dB of bit jitter reduction at 2F with an offset error of 1 5 nsec shift from the center of the data window i Recoverable within 16 retries Not recoverable within 16 retries 1 1 3 Performance Specifications CAPACITY FORMATTED UNFORMATTED Per Drive 29 9 MB 25 52 MB Per Surface 5 9 MB 6 38 MB Per Track 8 192 Bytes 19 416 Bytes s Access Time Seek Times Including Settling Single Track 19 67 msec Buffered Seek from last Step pulse to SEEK COMPLETE Average Seek 65 msec Full Seek 149 msec Tra
4. 4 K INDICATES CONNECTOR 5 22 2 e C tase comm pius 3 0 FIELD SERVICE AND ADJUSTMENTS SEAGATE disc drives do not require preventative maintenance 11 units shipped are covered by a one year factory warranty Should field service or adjustment become necessary certain restrictions apply Primarily the sealed Head Disc Assembly HDA must not be opened Seagate considers a drive to be out of warranty if the the HDA has been tampered with Any special tools or additional cautions will be treated under the appropriate sections This section of the 57425 Service Manual covers adjustments and procedures concerning field accessible components Any questions not treated in this document should be referred to your regional Seagate Technical Support office Field Support offices and their phone numbers are listed at the back of this handbook Should it become necessary to return a drive to Seagate Please ensure that the drive is shipped in the original container If that is not possible your Technical Support office will assist you in obtaining an approved container Please Note Shipping a drive in an unapproved container could cause damage and will void your warranty 25 3 1 Removals and Adjustments Note Removal of any assembly not covered in this section is not possible without special t
5. Manhattan House Bridge Road Maidenhead Berkshire SL6 8DB Telephone Maidenhead 0628 75851 Telex 847898 MANSKY Facsimile 0628 782812 ST425 WINCHESTER DISC DRIVE SERVICE MANUAL June 28 1984 Seagate 920 Disc Drive Scotts Valley 95066 408 438 6550 SECTION TABLE OF CONTENTS PAGE 1 0 1 1 Specification Summary reo nera 1 1 1 Physical Specifications ves ie 2 1 1 2 Reliability Specifications lt 1 1 3 Performance Specifications 4 1 1 4 Functional 4 2 8 THEORY OF 8 4 4 4 44 4 4 5 2 1 General Interface Description 45 6 2 1 1 Recording FPormat 2 1 2 Track ess essa esc 7 2 1 3 Read Write Headg ener ismi oan eB 2 1 4 DISOS oa 2 1 5 Air Filtration System severos 2 2 THEOL is 0919 2 3 2 2 1 Track 0 Sensor sains ecran 2 2 2 Index SensOr ee se ese i 2 2 3 Ground Spring wv rr soso eed Electrical Theory 6s vesc oe i 018 2 3 1 Main Control PC Board 20321 001 10 2 3 2 Microprocessor Operation 11 12 2 3 3 Drive Select eee eese eco oco eseseesl3 2 3 4 Read
6. When seeking the MPU evaluates the number of tracks to be covered and searches the PROM for the most efficient path Seeks longer than seven tracks involve a complex acceleration deceleration routine to optimize the motor and carriage characteristics Steps are accomplished by setting IC 2B to sequential phases IL provides both a current source and sink with the motor winding Near the end of a seek 2D and 2E are set to provide additional current to offset expected hysteresis Upon completion of a seek operation settling time is calculated based upon the length of seek and the interface line is activated in the specified time period With SEEK COMPLETE the MPU returns to the idle mode Whenever a seek operation crosses the write current switch boundary at Track 128 the microprocessor reduces the write current to the heads during write operations 2 3 3 Drive Selection Block Diagram TO INTERFACE FROM INTERFACE DRIVE SELECT 1 DRIVE SELECT 2 DRIVE SELECT 3 DRIVE SELECT 4 Functional Description DRIVE SELECT serves only to gate other signals to or from the drive interface Without DRIVE SELECT the drive cannot Read Write or Seek 13 2 3 4 Read Operation Block Diagram HEADSELECT Interface READ WRITE HEADS LOWPASS FILTER READ DATA CONVERSION DATA READ WRITE LSI IC 6H Interface Functional Description Head Select The binary decod
7. 100 Ohm R14 32 71 67 2 2 4 K Ohm R11 48 68 9 3 3 K Ohm R13 17 18 20 22 30 31 34 69 1 47 Ohm R18 e 78 2 6 2 K Ohm R23 26 71 1 220 Ohm R28 72 1 339 Ohm R29 73 1 51 Ohm R33 74 1 19 K Ohm R35 75 1 470 Ohm R36 76 2 4 7 K Ohm R37 38 77 4 3 K Ohm R41 67 68 69 78 3 2 K Ohm R42 46 61 79 1 150 Ohm R43 80 E 100 K Ohm R44 81 3 47 K Ohm R55 62 63 82 6 1 K Ohm R58 53 56 60 83 1 39 K Ohm R52 84 1 12 K Ohm R57 85 1 8 2 K Ohm R58 86 1 300 K Ohm R59 87 1 518 Ohm R12 88 1 39 Ohm R19 89 1 Resistor 1 4W 5 22 Ohm R70 34 5 8 FIELD SALES OFFICES CORPORATE HEADQUARTERS 920 Disc Drive Scotts Valley CA 95066 408 438 6550 TELEX 176455 SEAGATE SCVL NORTHWESTERN REGIONAL SALES 1150 North First Street 130 San Jose 95112 408 286 7580 SOUTHWEST REGIONAL SALES 5850 Canoga Avenue Suite 400 Woodland Hills CA 91367 213 884 2699 CENTRAL REGION SALES 9451 LBJ Freeway Suite 220 Dallas TX 75243 214 783 6711 TWX 758769 EASTERN REGIONAL SALES 435 King Street Littleton 81460 617 486 9711 SOUTHWEST REGIONAL SALES 9788 Koger Blvd Suite 319 St Petersburg FL 33702 813 577 1199 1 709049 Seagate UD EUROPEAN HEADQUARTERS Gassnerstrasse 5 8000 Munich West Germany 49 89 177017 524275
8. 2 The Index Sensor is mounted to the casting directly to the left of the spindle motor and may be removed by first freeing the LED connector from the front cover noting its orientation and then remove the Index Sensor clamp 26 w 8 To reinstall apply Loctite to the first three threads of the mounting screw Replace the Sensor clamp and screw but do not tighten Rotate the spindle motor until the silver index tab aligns with the Index Sensor Using the 030 shim adjust the gap between the Index Sensor and the index tab Tighten the mounting clamp screw and verify that the gap is 030 inch Route the Index Sensor wires through the retaining clip and reconnect the LED connector Replace the PC Board 3 1 3 Ground Spring Tools Required T 10 Torx Driver 1 2 3 4 Loctite 242 Remove Board see above With the front cover to your left the Ground Spring is at 12 00 o clock to the spindle motor and may be removed using the 10 Torx Driver When reinstalling apply Loctite to the first 3 threads of the mounting screw Verify that the Ground Spring contact button and the spindle motor ball are clean and making positive contact 3 1 4 Front Cover Tools Required 10 Torx Driver 1 2 3 4 Remove the PC Board see above Remove the four front cover mounting screws Disconnect the LED connector noting its orientation Remove the cover 3 1 5 Front Cover LED Tools Req
9. DRIVE SELECT 4 33 34 DIRECTION IN status enabled with DRIVE SELECT or Radial Option J2 P2 CONNECTOR PIN ASSIGNMENTS GROUND RTN SIGNAL PIN PIN DESCRIPTION 2 1 DRIVE SELECTED 4 3 RESERVED 6 5 RESERVED 8 7 RESERVED 41 Pin 16 19 9 NOT CONNECTED 12 11 GROUND 13 MFM WRITE 14 Write Data 16 15 GROUND 17 MFM READ DATA 18 READ DATA 20 19 GROUND J3 P3 CONNECTOR ASSIGNMENTS PIN 1 12 VOLTS PIN 2 12 VOLTS RETURN PIN 3 5 VOLTS RETURN PIN 4 5 VOLTS f 2 1 1 Recording Format The ST425 uses Modified Frequency Modulation MFM as the encoding method to record data This double density encoding scheme increases disc capacity by replacing clock bits with data bits Clock bits are written only when data bits are not present in both the preceding and current bit 11 Clock bits are written at the beginning of the bit 11 while data bits are written in the middle Due to predictable bit shift phenomena the 57425 requires pre compensation of write data on cylinders 128 through 305 This function must be provided by the controller to ensure data integrity at the specified error rate The data pattern determines which bits must be pre compensated The recommended amount of pre compensation is 12 nsec for both early and late written bits 11 other data patterns are written on time 2 1 2 Track Format The ST425 uses a slightly modified version of the IBM System 34 do
10. PAN HD SLT TORX DR dy EXTERNAL DA R RES on SCREW 1632 x 58 g WASHER FLAT 2 T BAR FIXED FLT PT SET HEX DR SCREW 2 56 x 1 4 BUT TORK DR STEPPE r PULLEY STEPPER SCREW SEAGATE TE NOLOGY MOTOR STEPPER SCREW 40 x 1378 BUT HO TORX DR gt Lot dii 227 youwren ON FAR SIDE Tite 5 eenz Eih SNOILWOOT ILNHNOdHOO 0 4 4 4 1 PRINTED CIRCUIT BOARD PART NUMBER 28321 9691 ITEM QUANTITY DESCRIPTION LOCATION 1 2 IC 7406 5E 6F 2 2 741514 6D 3F 3 3 7438 6 7 7 4 3 7445 2D 2E 2F 5 1 7474 5F 6 1 74123 4F 7 2 7415273 4A 4D 8 1 LM393 1B 9 1 6500 1 4c 19 1 Diode Array 36 11 1 Pre Amp 4G 12 1 Motor Spin Control LSI 5B 13 1 Read Write LSI 6H 14 1 MM2716 2K x PROM 4B 15 1 Stepper Motor Drive 2B 16 1 IC 7408 6E 77 1 Shunt 7 Position 18 2 Trans Array 2907 2H 2J 19 1 Resistor Pack l4 Pin DIP 220 330 Ohm 7D a 20 11 Resistor Pack l4 Pin DIP 680 1 2K Ohm 2G 21 1 CAP Ceramic 100 pf 5 NPO c5 22 1 330 pf 66 23 1 270 pf c12 24 1 39 13 25 1 47 C14 26 1 22 uf 5
11. or Waiting STEP DIRECTION SEEK COMPLETE HEAD SELECT 0 1 2 READY TRACK CONTROLLER ORIVE SELECT INDEX CIRCUIT MICROPROCESSOR 16500 MOTOR VOLTAGE Functional Description At power on the MPU initializes the stepper circuit to phase and resets all interface lines under its control Power is then applied to the Spindle Motor Control LSI and the index line is monitored for spindle rotation If rotation is not sensed within 15 seconds the assumes a problem and removes power the drive spins up 660 revolutions are counted before the MPU assumes that the drive is at speed and initiates recalibration If the heads are not over Track 0 the drive will step at 3 msec per track When both mechanical Track 0 electrical phase are present the drive is at true Track 0 and stepping will cease Within 20 msec both SEEK COMPLETE TRACK 0 and READY will go true and the drive is then ready to accept inputs from the controller When in the idle mode the MPU loops waiting for step pulses The MPU also monitors its RESET line pin 39 for a low to high signal from IC 4F which causes the MPU to reinitialize see above 11 Upon receiving Step pulse the MPU pauses for 500 usec to allow for additional pulses before executing the seek operation Every incoming pulse resets the 500 usec timer The seek operation will not begin until the last pulse is received
12. NPO 617 27 1 012 10 X7R C16 28 1 068 uf 19 X7R C18 29 26 CAP Ceramic 1 uf 480 203 C4 7 8 15 19 21 23 28 41 43 46 39 2 CAP Electrolytic 22 uf 16V 620 25 31 5 4 7 357 10 C9 11 24 26 32 1 CAP Ceramic 01 uf cl 33 1 CAP Ceramic 33 uf 50V 250 C47 34 1 Crystal 2MHz 1 i 35 1 Diode 4005 36 2 Inductor 2 2 uh 11 2 37 3 Inductor 10 uh L3 4 6 38 1 Inductor 3 3 uh L5 39 2 Transistor 2N3906 Q2 3 40 1 Transistor 2N3904 Q1 4 41 2 Transistor TIP129 05 6 42 1 Resistor Pack 10 Pin SIP 1 4W 560 Ohm 43 1 Resistor Pack 10 Pin SIP 1 4W 82 Ohm RP2 44 2 Resistor Pack 8 Pin SIP 1 2W 820 Ohm RP5 10 45 1 68 Ohm RP6 46 1 188 Ohm RP7 47 11 Resistor Pack 8 Pin SIP 1 2W 330 Ohm RP8 33 PRINTED CIRCUIT BOARD PART NUMBER 20321 001 48 1 Resistor Pack 8 Pin SIP 1 2W 470 Ohm RP9 49 2 Resistor Pack 8 Pin SIP 1W 10 Ohm RP3 4 59 2 Resistor 2W 5 2 Ohm R39 40 51 1 Resistor 1 2W 5 330 Ohm R5 52 1 Resistor 1 8W 1 357 Ohm R9 53 2 162 Ohm 7 8 54 1 30 1 Ohm R16 55 1 2 80 K Ohm R24 56 1 1 37 K Ohm R27 57 2 4 32 K Ohm R47 49 58 1 19 1 K Ohm R64 59 1 14 K Ohm R65 60 1 Resistor 1 8W 1 10 K Ohm R66 61 1 Resistor 1 8W 0 Ohm R21 62 1 Resistor 1 8W 1 54 9 Ohm R15 63 2 Resistor 1 4W 5 1 2 K Ohm 1 3 64 2 688 Ohm R2 4 65 1 5 1 Ohm R6 66 3
13. and 15 are ground 19 FIGURE 1 0 TEST POINT LAYOUT PC BOARD 28321 991 TEST POINT DESCRIPTION 1 amp 2 Differential Read Filter 4 Track Sensor 5 Index Sensor 11 12 13 14 15 Ground 29 lt gt 2 0 TEST POINT TIMING BOARD 20321 001 DIFFERENTIAL READ FILTER 160 mVolts 200 nsec TEST POINTS 1 amp 2 INDEX SENSOR TEST POINT 5 2 16 67 msec 1 1 3 Typ 21 2 5 57425 SCHEMATICS INDEX SECTION i PAGE 2 5 1 Main Control PC Board 20321 001 23 24 DATA WRITE DATA WRITE GATE READY COMP gt OC UNSAFE vor Bai ra ct me 1 aen L LR SPARES i 1 Te 146 1558 Fco leno 182 EC NOTES UNLESS OMERWISE SPECIFIES 1 RESISTANCE VALUES ARE IN OHMS Ww 5 2 Aut RESISTORS ARE Vaw CAPACITANCE VALUES ARE ERO HANDS
14. microinches at the OD The disc surface is coated with a flourocarbon lubricant 25 to 55 Angstroms in thickness The lubricant has sufficient abrasion resistance to withstand a minimum of 10 000 start stop cycles 2 1 5 Air Filtration System The 57425 incorporates captured air space air filtration system The 0 3 micron filter maintains Class 180 standards within the sealed Head Disc Assembly HDA and requires no maintenance during the life of the drive A filtered port allows ambient pressure equalization During normal operation there is no measurable air flow between the HDA and the outside environment 2 2 Mechanical Theory 2 2 1 Track 0 Sensor The Track 9 optical interrupter provides an output whenever the Winchester heads are positioned over Cylinder Zero This signal is used by the internal drive control electronics during the power on auto recalibrate routine The Track 0 signal is also output to the drive interface for use by the controller Note that the signal at the interface is really Track 0 The 8 2 2 1 2 2 1 Track Sensor Track 0 optical interrupter provides output whenever the Winchester heads are positioned over Cylinder Zero This signal is used by the internal drive control electronics during the power on auto recalibrate routine The Track 0 signal is also output to the drive interface for use by the controller Note that the sign
15. CTION The 57425 15 Seagate s 25 52 Megabyte 5 1 4 inch Winchester disc drive The ST425 has a formatted capacity of 20 0 Megabytes The ST425 is the newest addition to the ST400 family of disc drives and has the same interface power supply and controller requirements as the industry standard Seagate ST406 412 419 series Minislider heads and an advanced stepper motor design enable higher track density new head design allows increased bit packing which utilizes more of the disc surface High reliability is assured through the use of Seagate s proven metal band actuator stepper motor head positioner and a direct drive brushless DC spindle motor The spindle motor assembly is dynamically balanced and the Head Disc Assembly HDA is shock mounted to reduce vibration The low mass load force of the MiniWinchester heads and the lubricated oxide coated media provide reliable start stop operation Each disc surface is read by two read write heads The HDA which includes the read write heads discs and band actuator assembly is completely sealed and protected by a captured air space recirculation system employing a 0 3 micron absolute filter filtered port permits ambient air pressure equalization Thermal stabilization delays are unnecessary with the ST425 The spindle pump assures adequate air flow and uniform temperature distribution throughout the HDA This allows significantly greater off track margin and immediate read
16. RRENT LIMITER DYNAMIC BRAKE Refer to schematic on page 23 The sequence of normal operations is as follows Hall Effect Transducer Located inside the spindle hub This magnetic transducer senses spindle position and provides dynamic feedback proportional to the speed of the motor Two complete Square waves are generated each motor revolution This positional information is supplied to the spindle motor control LSI IC 5B pin 3 To prevent both phases of the motor from being selected simultaneously the motor control LSI inverts the Hall input to coil A Spindle Motor Control LSI When current is applied the spindle motor control LSI sets the motor speed to 3 600 RPM nominal This LSI integrates and transforms the error messages from the Hall effect transducer Using this information it outputs the correct current flow each revolution and corrects the motor phase driver at output pins 6 and 7 When power is interrupted the Motor Control LSI shorts both phases of the motor to ground allowing the motor generated back EMF to bring the spindle to a stop 18 ESS 2 3 2 Microprocessor Operation Block Diagram CONTROLLER CONTROLLER STEPPER CIRCUIT STEPPER MOTOR WRITE CIRCUIT SPINDLE SPEED CONTROL LSI 1 58 SPINDLE MOTOR The 57425 uses microprocessor to monitor and control internal drive functions and host interface lines The MPU has only three active modes Initializing Seeking
17. Write Gate is active Voltage and Head Comparator Select The Read Write LSI IC 6H constantly monitors both the 5 and 12 Volt lines to detect a low voltage condition If 5 Volts is gt 15 low or 12 Volts is gt 20 low the DC unsafe signal is activated IC 6H pin 25 causing write current to be disabled the microprocessor reset the fault line activated IC 6H pin 24 and the heads deselected If multiple heads are selected the Read Write LSI will disable the write circuitry and send a write fault to the interface IC 6H pin 24 18 2 4 Test Points 2 4 1 Test Point Data PC Board 20321 001 Test Points 1 and 2 Differential Read Filter Test Points 1 and 2 may be used to observe the Differential Read Data The typical amplitude of the signal resulting from adding the two channels is 169 mVolts The signal is observed at Cylinder Zero head 0 or 1 full track record of high frequency data 0000 or 1111 should resemble the diagram in Figure 2 0 Test Point 4 Track Sensor Test Point 4 may be used to monitor the Track 0 Sensor A high logic level indicates valid Track 0 The Track 0 Signal is valid for Cylinders 1 and 2 Test Point 5 Index Sensor Test Point 5 may be used to monitor the Index Sensor A high logic level is a valid Index indication Only the leading edge of the pulse may be considered valid The typical signal at TP 5 should resemble the diagram in Figure 2 0 Test Points 11 12 13 14
18. al at the interface is really Track 0 The Track 0 optical interrupter incorporates an infrared LED and an infrared sensitive photo transistor When the heads are positioned at Track 0 an interrupter arm attached to the stepper motor shaft breaks the light beam between the two components of the sensor The sensor will output a valid Track 0 signal as long as the beam remains broken 2 2 2 Index Sensor Once each revolution the Index Sensor provides an index pulse to the microprocessor for recalibration The ST425 Index Sensor is of the reluctance transducer type The sensor incorprates a built in preamplifier The case of the sensor is grounded which ties the drive DC returns to the drive casting The hub of the spindle motor has two metal tabs attached One is ferrous and the other which is mounted 1800 is non magnetic Each revolution of the spindle motor causes the ferrous tab to rotate past the sensor thereby inducing a pulse Note Please do not attempt to set the Index Sensor gap without referring to the appropriate section in the field service section of this manual 2 2 3 Ground Spring The 57425 incorporates a grounding contact between the spindle motor hub and the PC Board ground plane 2 3 Electrical Theory Main Control Board 20321 001 2 3 1 Motor Speed Control Block Diagram SPINDLE MOTOR CONTROL IC 58 MOTOR SPEED MOTOR SPINOLE INTEGRATOR DRIVERS MOTOR CU
19. er IC 2F selects the desired head based on the status of the 3 head select lines If the DC voltages are too low possibly causing an inaccurate write operation pin 12 will force the decoder to choose a nonexistent head During read operations the head center tap is set at approximately 5 Volts by the Read Write LSI IC 6H pin 27 By referencing 0 to 5 Volts actual ground appears as 5 Volts which eliminates the necessity of a negative power source normally required by the LSI preamp IC 4G LSI Preamp With the head center tap active data from the selected head will flow into the preamp This preamp amplifies the read signal and also acts as a high pass filter Low Pass Filter This filter network attenuates high frequency noise which is outside the normal data signal range Read Data Conversion Amplified data enters the Read Write LSI IC 6B at pins 1 and 2 and exits as high speed differential read data at pins 17 and 18 The Read write LSI functions are 1 Read data shifted 900 2 Analog to digital conversion 3 Erroneous data bits removed 4 Conversion of digital data to MFM differential data providing immunity to common mode noise during transmission 15 2 3 5 Write Operation Block Diagram FROM INTERFACE WRITE DATA PROCESSING READ WRITE LSI IC 6H READ WRITE HEADS MFM DIFFERENTIAL WRITE DATA HEAD SELECT Functional Description In
20. nsfer Rate 5 0 MBits sec Average Latency 8 33 msec 1 1 4 Functional Specifications Rotational Speed 3 600 RPM 1 Recording Density 19 568 Bits per inch Maximum Flux Density 19 568 Flux changes per inch Maximum Track Density 550 Tracks per inch Cylinders 306 Tracks 2 448 Read Write Heads 8 Discs 2 2 8 THEORY OF OPERATIONS 2 1 General Interface Description The 57425 Winchester supports the Seagate ST506 412 Interface The interface consists of a 34 pin control connector a 20 pin read write connector and a 4 pin DC connector The 34 pin connector provides 10 control signals to the drive and returns 5 status signals to the controller The 20 pin connector handles the Modified Frequency Modulation data to from the drive and supplies the drive selected status to the controller The 4 pin connector provides 5 and 12 Volts DC In general the control connector is daisy chain terminated throughout the user system while the read write connector is terminated radially The following tables indicate the 57425 interface requirements J1 P1 CONNECTOR PIN ASSIGNMENTS GROUND RTN SIGNAL PIN PIN DESCRIPTION 1 2 RESERVED 3 HEAD SELECT 22 5 6 WRITE GATE 7 8 SEEK COMPLETE 9 19 TRACK 0 11 12 WRITE FAULT 13 14 HEAD SELECT 29 15 16 RESERVED 42 Pin 7 17 18 HEAD SELECT 2 19 20 INDEX 21 22 READY 23 24 STEP 25 26 DRIVE SELECT 1 27 28 DRIVE SELECT 2 29 30 DRIVE SELECT 3 31 32
21. ools and clean room facilities BEFORE PERFORMING ANY OPERATION LISTED BELOW PLEASE PROVIDE A CUSHIONED WORK SURFACE 3 1 1 PC Board Tools Required T 19 Torx Driver 1 Place the drive on a padded surface PC Board up and with the front cover to your left 2 Remove the front cover by removing 4 mounting screws 3 Disconnect the Front panel LED by removing the two wire connector 4 Disconnect P6 P7 and P8 located at the left edge of the PC Board noting their position 5 Disconnect the Printed Cricuit Cable J5 located at the upper edge of the PC Board 12 99 o clock 6 Disconnect th spindle motor cable P4 located on the lower edge of the PC Board 6 00 o clock 7 Slide the PC Board out to the right Note It is recommmended that the replacement PC Board be powered up with the head cable P5 disconnected This will ensure that a damaged replacement does not alter data on the disc To determine if the Board is good the Write Fault signal can be monitored at the junction of the inverter and R113 If a high logic level exists at junction R113 then a No Write Fault condition exists and the PCB can be powered down and P5 connected Avoid creasing the Printed Circuit Cable when removing P5 Inspect the cable after this operation 3 1 2 Index Sensor Tools Required 10 Torx Driver Loctite 242 030 shim Note This procedure may result in a loss of recorded data 1 Remove the PC Board see above
22. order to WRITE the following conditions must be true 1 Write Fault inactive 2 Drive Select active 3 Drive Ready active 4 Seek Complete active 5 Write Gate active Write Gate A write sequence is initiated when Write Gate is activated which causes the Read Write LSI IC 6H pin 26 to apply 12 Volts to the selected head s center tap At the same time data is sent to the Read Write LSI pins 15 and 16 16 Write Data Processing Differential write data which is precompensated MFM is received from the host controller by the Read Write LSI and changed to single line pulse data Depending whether plus or minus data is to be written the Read Write LSI activates either pin 7 or 8 of the pre amp LSI IC 4G The amount of current to be written is established by the Read Write LSI When writing to the inner heads 2 and 3 write current is reduced to lessen the problems of pulse crowding 17 2 3 6 Fault Detection Block Diagram DC POWER Interface VOLTAGE COMPARATOR MICROPROCESSOR HEAD SELECT COMPARATOR peser HEAD SELECT Interface WRITE FAULT READ WRITE LSI Interface WRITE GATE SEEK COMPLETE READY Interface Functional Description Any combination of the following events will cause a Write Fault condition and will prevent the drive from writing 1 Multiple heads selected 2 DC voltages greater than 29 low 3 Seek Complete or Ready inactive when
23. uble density format This format is common to many industry standard floppy disc drives When formatted each sector is identified by a unique identification field containing cylinder head sector information address mark and error checking polynomials The Seagate format uses Cyclic Redundancy Checking CRC for error correction This format also allows for a plus or minus speed variation of aproximately 3 The specification for spindle speed variation is 1 over the specified environmental and power limits 2 1 3 Read Write Heads When operational the read write heads fly on an air bearing created by the rotating disc There is no dedicated landing zone The head and flexure supporting arm are designed for contact start stop operation The Winchester heads are loaded toward the disc surface at 9 5 1 grams This is a typical value to allow the required stability in all operating conditions typical flying height measured at an inner radius is 15 2 microinches At an outer radius the height is 25 3 microinches The head flexure assembly incorporates a low mass design that is resistive to head and or media damage 2 1 4 Discs The 57425 employs two non removable double sided 5 1 4 inch discs These discs are designed using current iron oxide technology Disc dimensions are 40mm inside diameter by 1l130mm outside diameter The thickness of the magnetic coating is 20 microinches at the ID and increases linearly to 40
24. uired T 19 Torx Driver Note water base hot melt glue may be used to secure the LED grommet assembly 1 2 3 Remove the PC Board see above Remove the connector from the Front Cover LED noting the orientation of the connector Remove the LED and grommet from the Front Cover noting the orientation of the LED 27 3 1 6 Frame Tools Required T 19 Torx Driver 1 orient the drive PC Board up and front cover to your eft 2 Remove the PC Board see above 3 Remove the Front Cover see above 4 Free the ground strap jumper located on your right from the frame 5 Remove the three shock mounting screws and lift the frame up leaving the Head Disc Assembly HDA on the padded surface If it is necessary to transport the HDA please keep it strapped down to the drive pallet to avoid excessive shocks 3 1 7 Track 0 Sensor Tools Required T 19 Torx Driver Proper positioning of the Sensor is essential The adjusting set screw is set at the factory and should not be tampered with l Remove the Front Cover see above 2 Disconnect P8 Position the drive on edge with the stepper motor up Remove the Track Sensor mounting screw using the T 19 Torx driver Remove Sensor When reinstalling apply Loctite to the first three threads of the mounting screw au 28 lt 4 8 ILLUSTRATED PARTS CATALOG INDEX SECTION d PAGE 4 1 Interface
25. write ability after power up Only DC voltages 5 and 12 DC are required All electronics are packaged a single printed circuit board The board is mounted outside the sealed media area allowing easy field access without risking media integrity Simplification of mechanical and electrical design provides a projected service life of more than 11 000 hours Mean Time Between Failures MTBF 1 1 SPECIFICATION SUMMARY 1 1 1 Physical Specifications Environmental Limits Ambient Temperature Limits Operating 590 to 1130F 100 to 450C Non Operating 490 to 1400 400 to 690C Maximum Temperature Gradient Operating 180F hour 190C hour Non Operating Below Condensation Relative Humidity 8 to 80 non condensing Maximum Wet Bulb 78 80F 260C Maximum Elevation Operating 1 000 feet to 10 000 feet Non Operating 1 000 feet to 30 000 feet Maximum Shock Without Incurring Physical Damage 11 msec shock pulse half sine wave Operating Longitudinal 3 G S Lateral 5 G s Vertical 7 G s Non Operating 35 G s No mechanical damage will occur within the above specified limits Maximum Vibration Without Incurring Soft Errors Operating Frequency 2 22 Hz 010 double amplitude 22 509 Hz 0 25 G peak 500 22 Hz 8 25 G peak 22 2 Hz 010 double amplitude Maximum Vibration Without Incurring Physical Damage Non operating Frequency 2 22 Hz 040 double amplitude 22 500 Hz 1 9 G peak 599 22 Hz 1 9 G peak
Download Pdf Manuals
Related Search