OEM OPERATING AND SERVICE MANUAL TM848-1 AND TM848-2...

OEM

OPERATING AND SERVICE MANUAL

TM848-1 AND TM848-2 DISK DRIVES

48 TRACKS PER INCH

mn d u n coRpoRATIDN20320 PRAIRIE STREETCHATSWORTH, CA 91311

TELEPHONE NO.: ( 2 13) 993-6644TWX NO.: 91 0 494 1 721TEL.EX NO.: 194794

COPYRIGHT 1982 TANDON CORPORATION

The information contained in this document is the property ofTandon Corporation. It may not be duplicated in full or part byany person without prior written approval. The material in thisdocument is provided for informational purposes, and is subjectto change by Tandon Corporation.

TABLE OF CONTENTS

SectionNumber

PageNumberTitle of Section

SECTION I INTRODUCTION TO THE TM848 FAMILY OF DISK DRIVES

l .1.11.21.31.41.51.61.71.81.91.101.10.11.1 0.21.1 0.31.111.121.131.141.151.1 5.11.1 5.21.1 5.31.1 5.41.1 5.51.1 61.1 6.11.1 6.21.171.1 7.11.1 7.21.1 7.31.181.191.1 9.11.1 9.21.1 9.31.1 9.41.1 9.51.1 9.61.1 9.71.1 9.81.1 9.91.1 9.1 01.1 9.1 11.1 9.1 21.1 9.1 31.1 9.1 41.1 9.1 51.1 9.1 61.1 9.1 7

Introduction.Purpose Of The DrivePhysical Description of The DriveFunctional Description of The DriveDiskettesMechanical and Electrical SepcificationsPower RequirementsInterface Circuit SpecificationsIncoming Inspection Checks and ProceduresInterface ConnectionsMounting The Drive.Hardware .Dust CoverCooling System Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . .Diskette Care, Handling and Storage .Write Protect.O peration of The Drive . . . . .Organization of The DriveComponents of The DriveIndex PulseDrive Status Logic .Spindle Drive SystemPositioner ControlData ElectronicsInterface ElectronicsInterface Connector Pin Assignments, P13.Power Connector Pin AssignmentsTerminated Lines .Input Line Terminations From Removable Resistor Pack.Drive Select.Program Shunt.DS and HL Power Save OptionsUser-Selectable Options ..Drive Select DS1-DS4.Side Select Options Using Drive Select 1B-4B .In Use From Drive Select .In Use From Head Load . .Ready Alternate Output PadRadial ReadyReady Modified.Radial IndexIndex Alternate Output PadIn Use Altenate Output PadDiskette Lever Lock Latch OptionDisk ChangeTwo-Sided Diskette Installed.Stepper Power From Drive SelectStepper Power From Head Load LineHead Load Alternate Output Pad OptionRadial Head Load Signal Option.

. 1-1

. 1-1

. 1-1

. 1-1

. 1-2I-2

. 1-2

. 1-2

. 1-21-5

. 1-5

. 1-6

. 1-6.. 1-6

1-61-71-71-71-71-81-81-91-91-91-121-121-121-141-141-14

.. 1-141-171-1 71-181-181-181-181-181-1 9

. 1-191-1 91-201-201-201-201-201-211-211-211-21

SectionNumber

1.1 9.1 81.1 9.1 91.1 9.201.1 9.211.1 9.22

S ECTION II MAINTENANCE CHECKS AND ADJUSTM E N TS

PageNumber

1-211-211-221-221-22

Title of Section

Inhibit Write When Write ProtectedAllow Write When Write Protected .Head Side Select Options S1 - S3Spindle Motor Control Options M1 - M4Motor Control Select Options MC1 - MC4.

2.2.12.1.12.22.2.12.32.42.4.12.4.22.4.32.52.62.72.8

SECTION II I PRIN T E D CIRCUIT BOARD OPERATION

Introduction.Spindle Drive Motor Checks and Adjustments. . .Long-Term Drive Motor Speed Checks and AdjustmentsCats Eye Alignment Check and AdjustmentCats Eye Alignment Check.Head Carriage AdjustmentIndex Sensor Checks and AdjustmentsIndex-To-Data Burst ChecksIndex Sensor AdjustmentIndex Pulse Width CheckTrack 00 Sensor Check and Adjustment .Amplitude Check.Azimuth CheckLoad Arm Adjustment

2-12-12-12 22-42-52-62-62-72-82-82-92-102-10

Introduction.Physical Description of The Circuit Board.Interface Electronics SpecificationsInput Control LinesO utput Control Lines . . . . . . .

.. 3-1

.. 3-13-13 2

.. 3-7

3.3.13.23.33.4

SECTION IV T R OU B LESH O O TING GUIDE

4.4.14.14.34.44.54.64.7

SECTION V REPL AC EM ENT PROCEDURES

Introduction.Not Ready and/or No Index.W ill Not Seek or Restore. . . .Will Not WriteWill Not Read.Activity L.E.D. InoperativeNo Track 00 Sensor Indication.Drive Motor Will Not Start When Door Latched .

.. 4-1

.. 4-2

.. 4-2

.. 4-34-3

. 4-3

. 4-4

. 4-4

Introduction.Drive BeltDrive Motor .Circuit Board.Cone AssemblyDiskette Lever .Bridge AssemblyBezel

5-15-1

.. 5-25-3

.. 5-4

.. 5-65-6

.. 5-8

5.5.15.25.35.45.55.65.7

SectionNumber

PageNumberTitle of Section

Activity L. E. DLoad Arm Assembly.Track 00 Sensor Assembly.Write Protect Sensor AssemblyDoor Switch AssemblyIndex Sensor Assembly.Diskette Ejector Assembly .Load Resistor AssemblyStepper Band.Stepper Motor AssemblyHead Carriage Assembly

5.85.95.105.1 15.1 25.1 35.1 45.1 55.'I 65.1 75.'I 8

APPENDIX I PRINTED CIRCUIT BOARD SCHEMATICS AND ASSEMBLY

5-95-1 0

. 5-105-1 15-1 2

. 5-125-1 45-1 55-1 6

. 5-185-1 9

DRAWINGS ..

11-1APPENDIX II RECOMME N DED SPARE PARTS LIST..

LIST OF ILLUSTRATIONS

FIGURES

FigureNumber

PageNumber

5-15-25-35-45-55-65-75-85-9

1-11-21-31-41-51-61-71-81-91-10

2-12-22-32-42-52-62-72-82-92-102-1 12-1 2

3-13-23-33-43-53-63-73-83-93-1 03-1 13-1 2

Title of Figure

TM848 Disk Drive Mounting Configuration.TM848 Disk Drive Functional Block Diagram.FM Recording Magnetization ProfilesWrite Operation Timing DiagramRead Timing Diagram.Circuit Board AssemblyGeneral Control and Data Timing RequirementsRadial Ready Installation .Radial Index InstallationRadial Head Load Signal.

Circuit Board AssemblyHub Center Line and Track LocationsCats Eye Pattern.Head Module Retaining and Cam Screws..Index-to-Data BurstIndex Sensor's Retaining Screw and Adjustment.Negative Going Pulse Width .Track 00 Sensor ..Optimum Head Azimuth Alignment.Head Azimuth Alignment Acceptable Lower LimitsHead Azimuth Alignment Acceptable Upper LimitsLoad Arm Adjustment, Front View

Printed Circuit Board.Interface Configuration .Select Lines Schematic Diagram.Write Data Circuit Block DiagramTrim Erase Diagram.Side Select Schematic Diagram.Index Schematic Diagram.Waveform at Test Point 7, Soft Sectored.Track 00 Schematic DiagramWrite Protect Schematic Diagram.Read Circuit Block Diagram.Read Data Schematic Diagram.

Drive Belt and SpindleDrive Motor and Related PartsCircuit Board Mounting ScrewsCone Assembly Key PartsCone Assembly PartsDiskette Lever Key PartsDiskette Lever AdjustmentBridge Assembly Key PartsBridge Assembly Additional Key Parts

3-13-13-23-63-8

.. 3-93-1 1

. 3-1 13-1 23-1 3

.. 3-143-1 5

1-61-91-101-111-121-151-161-191-201-21

2-22-32-42-52-72-72-82-92-1 12-1 12-122-1 2

5-25-3

.. 5-4

.. 5-5

.. 5-55-65-75-75-8

FIGURES

FigureNumber

5-1 05-1 'I5-1 25-1 35-145-1 55-1 65-1 7

PageNumber

5-8.. 5-9.. 5-10

5-1 15-1 2

.. 5-135-1 3

. 5-14

5 5-1 8

et Fi ereT i t l eBezel and Related PartsActivity L. E. D. Key PartsLoad Arm Assembly Key PartsTrack 00 Sensor Assembly Key PartsWrite Protect Sensor Assembly Key Parts. .Door Switch Assembly Key Parts .Index Sensor Assembly Key Parts, Top View.Index Sensor Assembly Key Parts, Bottom View.

Diskette Ejector Assembly Key PartsLoad Resistor Assembly and Key PartsStepper Band Key PartsStepper Band Additional Key PartsS tepper Motor Assembly Key Parts.. . . . .Head Carriage Assembly Key Parts

TABLES

5-155-1 65-1 75-1 85-1 95-20

5-1 95-205-215-225-23

TableNumber

PageNumberTitle of Table

Mechanical and Electrical SpecificationsPower RequirementsInterface Connector Pin Assingments. .Power Connector Pin AssignmentsOptions

Drive Interface Lines and Pin ConnectorsStepper Logic Truth Table .

1-31-41-131-141-17

3-33-5

1-11-21-31-41-5

3-13-2

SECTION I

INTRODUCTION TO THE TM848 FAMILY OF DISK DRIVES

INTRODUCTION

This section contains a description of the physical and functional specifications for the TM848-1 and2 disk drives, 48 tracks per inch (TPI), manufactured by Tandon Corporation.

1.1 PURPOS E OF THE DRIVE

The drive is an eight-inch disk memory designed for random access data entry, storage, and retrievalapplications. These applications typically are intelligent terminal controllers, microcomputers, wordprocessing systems, data communications systems, error logging, microprogram loading, point-ofsale terminals, and Winchester back ups.

The drive is capable of recording and reading digital data, using FM, and MFM.

PHYSICAL DESCRIPTION OF THE DRIVE1.2

The drive can be mounted in any vertical or horizontal plane. However, when mounted horizontally,the printed circuit board must be up.

The spindle is belt driven by a brushless D.C. motor with an integral tachometer. The servo controlcircuit, suitably sized pulleys, and the tachometer control the speed of the spindle. The Read/Write,double-sided head assembly is positioned by means of a stepper motor, split band, and a pulley.

The Read/Write/Erase head assembly is a glass-bonded manganese/zinc ceramic structure. It has alife in excess of 20,000 hours.

For diskette loading, operator access is provide via a slot located on the front of the drive.

The electronic components of the drive are mounted on a c i rcuit board assembly located in thechassis. Power and interface signals are routed through connectors that plug into the back of the drive.

1.3 FU NC TIONAL DESCRIPTION OF THE DRIVE

The drive is fully self-contained. It requires no operator intervention during normal operation. Thedrive consists of a spindle drive system, a head positioning system, and a read/write/erase system.

The TM848-1 is a s ingle-sided drive. The TM848-2 is a double-sided drive. The only differencebetween the two drives is the number of heads. The circuit board is identical in both models.

When the diskette lever is opened, access is provided for the insertion of a diskette. The diskette isaccurately positioned by plastic guides. The disk position is ensured by the backstop and disk ejector.

Closing the diskette lever activates the cone/clamp system, resulting in centering of the diskette andclamping of the diskette to the drive hub. The drive hub is driven at a constant speed of 360 RPM by aservo-controlled brushless D. C. motor. The head is loaded into contact with the recording mediumwhenever the diskette lever is latched.

1-1

The head is positioned over the desired track by means of a stepper motor/band assembly and itsassociated electronics. This positioner employs a 3.6 degree rotation to cause a one-track linearmovement. When a write-protected diskette is inserted into the drive, the Write Protect sensordisables the write electronics of the drive, and a Write Protect status output signal is available to theinterface.

When performing a write operation, a 0.013-inch wide (nominal) data track is recorded. This track isthen tunnel erased to 0.012 inch (nominal).

Data recovery electronics include a low-level head amplifier, a differentiator, a zero crossingdetector, and digitizing circuits.

No data-clock separation is provided.

In addition, the drive is supplied with the following sensor systems:

1. A track 00 sensor that senses when the Head Carriage Assembly is positioned at Track 00.

2. The two index sensors, each of which consists of a L.E.D. light source and a phototransistor,are positioned so that a signal is generated when a index hole is detected. The drive candetermine whether a single- or double-sided diskette is installed. This output signal is presentat the interface.

3. The Write Protect sensor disables the drive's write electronics whenever a write-enable tab isremoved from the diskette (see Section 1.12).

1 .4 DISKET T ES

The drive uses a standard eight-inch diskette. Diskettes are available with a single index hole or withindex and sector holes. They also are available double- or single-sided.

Single index hole diskettes are used when sector information is pre-recorded on the diskette (softsectoring). Multiple index hole diskettes provide sector pulses by means of the index sensor andelectronics (hard sectoring).

1.5 M EC H AN ICAL AND ELECTRICAL SPECIFICATIONS

The mechanical and electrical specifications of the drive are listed in Table 1-1.

1.6 POW ER R E Q UIREMENTS

The power requirements of the drive are listed in Table 1-2.

1.7 INTERF ACE CIRCUIT SPECIFICATIONS

The interface circuits are designed so that a disconnected wire results in a false signal.

Levels:True = +0.4 V, maximumFalse = +2.4 V, minimum

1.8 IN C O M ING INSPECTION CHECKS AND PROCEDURES

There are two kinds of recommended incoming inspection checks and procedures: sta t i c anddynamic ones.

The static incoming inspection checks include the minimum steps that should be taken to ensurethat the drive is operational when received.

1-2

TABLE 1-1

MECHANICAL AND ELECTRICAL SPECIFICATIONS

MECHANICALHeight: 2 .30 inchesW idth: 8 in c h e s

Length: 13 .125 inches behind front panelWeight: 5.5 pounds

ELECTRICAL

+ 5 V D. C. Power:+24 V D. C. Power:

Selected Motor On:Dese lected:Spindle Motor:Start Current Surge:

ENVIRONMENTAL

Operating Temperature:Storage Temperature:Wet Bulb Temperature:Noncondensing Operating Humidity:

R E L I A B I L I TY

+5 volts 2 5 percent, 0.75 amp typical+24 volts+ 10 percent0.75 amp typical0.20 amp typical0.40 amp typical2.5 amps, 400 msec on, 24 volts total

4.4'C to 46'C (40 F to 115 F)— 40'C to 71'C ( — 40 F to 160 F)26 C (78'F) maximum20-to-80 percent

MTBF:MTTR:

Error Rates:Soft Read:Hard Read:Seek Errors:

PERFORMANCE

Head Wear Guarantee:Number of Tracks:Track-To-Track Access Time:Head Settling Time:Average Access Time,

including head sett l ing time:Motor Start Time:Disk Rotational Speed:Instantaneous Speed Variation:Flux Changes Per Inch, Inside Track:

Transfer Rates:

Linformatted Recording Capacity:

1 in 10' bits1 in 10" b i ts1 in I 0' seeks

10,000 power-on hours30 minutes

IBM Format Recording Capacity:

15,000 media hours77 for TM848-1; 154 for TM848-2, 77 per surface3 milliseconds15 milliseconds

91 milliseconds700 milliseconds360 RPM+ 1.0 percent6536 FCI, Side 0, both models;6818 FCI, Side 1, TM848-2 only250K BPS single density, 500K BPS

double density0.8 MBytes per disk, single density,

double-sided drive1.6 MBytes per disk, double density,

double-sided drive0.6 MBytes, single density, double-sided

drive1.2 MBytes, double density, double-sided

driveFM single density, MFM double densityRecording Method:

1-3

TABLE 1-2

POWER REQUIREMENTS

1. + 5 V o l t s :

2. +2 4 Vo l ts: After motor start interval

0.70 Amps typical

Spindle Moto r 0 .3 5 A m ps typical

Stepper Moto r 0.4 0 A mps typicalElectronics 0.17 Amps typical

Total 0.92 Amps typical

3. +2 4 Vo l ts: During motor start interval

a. Configured for stepper motor enabled during motor start.2.5 Amps typical surge.

2.5

2.0

1.5

1.0

0.5

100 200 300 400 600500

TIME (MILLISECONDS)

b. Configured for stepper motor disabled until motor comes up tospeed. 2.1 Amps typical surge.

2.5

2.0STEPPER MOTORENABLED

1.5

1.0

0.5

200 300 400 500 600100

TIME (MILLISECONDSI

1-4

A. Inspect the shipping package for obvious damage.

B. Open the shipping container, and remove the drive.

C. Inspect the drive's overall appearance. Ensure that there are no scratches on the bezel.

D. Ensure that all internal connectors are seated properly.

E. Turn the diskette lever counterclockwise, and remove the shipping diskette.

F. Insert a blank diskette, close, and then open the diskette lever. The diskette should eject.

G. Insert a blank diskette, and manually turn the spindle pulley. It should rotate freely.

The dynamic incoming inspection procedures include:

A. Connect the drive to an exerciser or computer tester capable of seeking, writing, and reading.

B. Power up the test equipment, and apply power to the drive.

C. Select the drive, and ensure that the Activity L. E. D. located on the bezel il luminates.

D. Insert a work diskette and write/verify from Track 00 to Track 76. Ensure that there are noerrors.

E. Insert a diskette written previously on another drive. Read this diskette, and ensure that thereare no data errors. If excessive errors occur, check the diskette on the drive on which it waswritten.

F. If the drive passes all the checks listed above, it is operational. If not, review Section II.

INTERFACE CONNECTIONS1.9

Signal connections for the dr ive are made via a user-supplied 50-pin, flat ribbon connector (3MScotchflex 3415). This connector mates directly with the circuit board connector at the rear of thedrive. The D. C. power connector is a six-pin connector (Amp Mate-N-Lok Part Number 1-480270-0),which mates with the connector at the rear of the drive.

The signal connector harness should be of the flat ribbon or twisted pair type, have a maximum lengthof ten feet, and have a 22-to-28 gauge conductor compatible with the connector that is to be used.

Power connections should be made with 18-AWG cable, minimum.

1.10 MO UNTI NG THE DRIVE

The drive has been designed to mount in any plane, i.e.: upright, horizontal, or vertical. The onlyrestriction is that the printed circuit board side of the chassis must be uppermost when the drive ismounted horizontally. Eight holes are provided for mounting: two on each side and four on the bottomof the housing (see Figure 1-1). The two on each side are tapped for 8-32 screws. The four mountingholes on the bottom require 8-32 thread forming screws.

Optional straps are available to permit attaching two drives together for installation in standard widthdrive openings.

1-5

0o

6-32 THDTHRLI 4 PL(2 EA. SIDE)

0

8.00

13.33

3.50

0 '0149 DIA. TOP X1 56 DIA. BOTTOM X.430 DP.4 PL

O .P3

pp I 206 ~

I

8 550 1 60

2.300

NOTES. DIMENSIONS GIVEN IN INCHES.

Figure 1-1TM848 Disk Drive Mounting Configuration

1.10.1 Hardw a re

The drive is manufactured with certain critical internal alignments that must be maintained. Hence, itis important that the mounting hardware does not introduce significant stress on the drive.

A three-part mounting scheme is recommended. Any mounting scheme in which the drive is part ofthe structural integrity of the enclosure may cause equipment operating problems and should beavoided. In addit ion, the mounting scheme should al low for adjustable brackets or incorporateresilient members to accommodate tolerences.

1.10.2 Dust C over

The design of an enclosure should incorporate a means to prevent contamination from loose itemse.g., dust, lint, and paper since the drive does not have a dust cover.

1.10.3 Co o l i ng System Requirements

Heat dissipation from a single drive is normally 30 watts (102) Btu/Hr.) under high line conditions.When the drive is mounted so that the components have access to the f ree f low of a ir, normalconvection cooling allows operation over the specified temperature range.

When the drive is mounted in a confined environment, air flow must be provided to maintain specifiedair temperatures in the vicinity of the motors, the circuit board, and the diskette.

1.1 1 D ISKETTE CARE, HAND LI NG, AND STORAGE

It is important that the diskette be cared for, handled, and stored properly so that the integrity of therecorded data is maintained. A damaged or contaminated diskette can impair or prevent recovery ofdata, and can result in damage to the read/write heads of the drive.

1-6

The following list contains information on how the diskette can be cared for, handled, and stored.

1. Keep the diskette away from magnetic fields.

2. Do not touch the precision surface of the diskette with fingers.

3. Insert the diskette carefully into the drive until the backstop is encountered.

4. Do not bend or fold the diskette.

5. Put the diskette into its jacket when it is not in use.

6 . Store the diskette at temperatures between 10'C and 52'C or 50'F and 125'F.

1.12 W RITE P ROTECT

The drive is equipped with a Write Protect Sensor Assembly. This sensor operates in conjunction witha diskette that has a slot cut in the protective jacket.

When the slot is uncovered, the diskette is write protected. The slot must be covered to write on thediskette. An option is available on the board for defeating the write protect sensor.

1.13 OPERA T ION OF THE DRIVE

The drive consists of the mechanical and electrical components necessary to record and to readdigital data on a diskette. User-provided D.C. power at+24 volts and+5 volts is required for operationof the drive.

1.14 ORGAN I Z ATION OF THE DRIVE

All electrical subassemblies in the d r ive are constructed with leads that te rminate in mu l t ipinconnectors, enabling the individual assemblies to be removed.

The heads are connected to the circuit board via cables that terminate in five-pin female connectorsand their associated male sockets that are located in c lose p roximity to the read/wr ite dataelectronics.

Interface signals and power are provided via connectors at the rear of the drive.

1.15 CO MPON E NTS OF THE DRIVE

The drive consists of six functional groups:

1. Index Pulse Shaper

2. D rive Status Log ic

A. Write Protect

B. Track 00 Sensor

C. Double-sided Disk

D. Ready

E. Disk Change

1-7

3. Spindle Drive Control

4. Carriage Position Control

5. Write/Erase Control

6. Read Amplifier and Digitizer

Figure 1-2 is a functional block diagram of the drive. It should be referred to in conjunction with thefollowing sections. The data in the ensuing figures is primarily represented in simplified form.

1.15.1 Inde x P u lse

An index pulse is provided to the user system via the index pulse interface line. The index circuitryconsists of an index L. E. D., an index phototransistor, and a pulse shaping network. As the index holein the disk passes an index L. E. D. phototransistor combination, light from the L. E. D. strikes the indexphototransistor, causing it to conduct. The signal from the index phototransistor is passed on to thepulse shaping network, which produces a pulse for each hole detected. This pulse is presented to theuser on the index pulse interface line.

1.15.2 Dr i v e Status Logic

There are five drive status logic lines: Write Protect, Track 00 Sensor, Two-Sided Ready and DiskChange.

A. Write Protect

A write protect signal is provided to the user's system via the write protect interface line. Thewrite protect circuitry consists of a write protect sensor and circuitry that routes the signalthat is produced.

When a write protected diskette is inserted in the drive, the sensor is activated and the logicdisables the write electronics and supplies the status signal to the interface.

B. Track 00 Sensor

The level on the Track 00 interface line is a function of the position of the head assembly.When the head is positioned at Track 00 and the stepper motor is at the home position, a true(low) level signal is generated at the interface.

C. Two-Sided Disk

This signal is low(true) when the drive is selected and has detected the presence of the IndexTwo hole in the diskette currently installed.

D. Ready

This signal is true when Drive Select is low (true) if the spindle drive is up to speed and thedrive is ready to read and write.

E. Disk Change

This signal is true when Drive Select is low (true) if the diskette lever has been moved to theopen position after the previous drive select went false.

1-8

1.15.3 Sp in d le Drive System

The spindle drive system consists of a spindle assembly driven through a drive belt by a brushlessD.C. motor/tachometer.

The servo electronics required for speed control are located on the printed circuit board.

The control circuitry contains an interface control line. When the drive motor control interface line isfalse (high), the drive motor is allowed to come up to speed.

READY

INDEX SENSORL.E.D.'S ~

CONTROLLOGIC

INDEX

DISK CHANGE

TWO SIDEDD.C.STEPPERMOTOR

WRITE PROTECT

TRACK 00WRITE PROTECT

SENSOR+L.E.D. IN USEINDEX DETECTORS

SIDE SELECT

HEAD CARRIAGEAND STEPPERBANDASSEMBLY

WR ITEPROTECT

DETECTOR DRIVE SELECT

SPINDLEMOTOR

CONTROL

MOTOR CONTROL

D.C. DRIVEMOTOR

WRITE GATE

WRITE DATAWRITELOGIC

CURRENT SWITCH

READLOGIC

READ DATA

DIRECTIONSTEPPERMOTOR

CONTROL STEP

Figure 1-2TM848 Disk Drive Functional Block Diagram

1.15 4 Po si t i oner Control

The head positioning system uses a bipolar-driven motor drive, which changes one phase for eachtrack advancement of the read/write carriage. In addition to the logic necessary for motor control, agate is provided that inhibits positioner motion during a write operation.

1.15.5 Data E l ec tronics

Information can be recorded on the diskette by using a double-frequency code. Figure 1-3 illustratesthe magnetization profiles in each bit cell for the number sequence shown for FM recording.

1-9

BIT PATTERN~ BIT C E LLP+ )0 1 0

III

IC )D C

I )I I

I I I ) ) ) )

)0 I

III

1

II )I )

MAGNETIZATION

WRITE DATA

D /C

I

III

D ICI

c I c

I I

D CI

I I

II I I I

MAGNETIC ELEMENTS N S S N N S SS S N N S S

I I ) II I I ) ) I

I I • I ) I s I) I I

Figure 1-3FM Recording Magnetization Profiles

The erase gaps provide a guard band on either side of the recorded track.

All signals required to control the data electronics are provided by the user system and are shown inthe TM848 drive functional block diagram (see Figure 1-2). These control signals are:

1. Select

2. Write Gate

3. Write Data

4. Side Select

5. Write Current Switch

Composite read data is sent to the user system via the Read Data interface line.

A. Data Recording

The write e lectronics consist o f a s w i t chable wr ite cu r rent source, a w r ite waveformgenerator, an erase current source, the trim erase control logic, and the head selection logic(see Appendix I).

The read/write winding on the head is center-tapped. During a write operation, current fromthe write current source flows in alternate halves of the winding, under control of the writewaveform generator.

The conditions required for recording, i.e. drive ready must be established by the user'ssystem, as follows:

1. Drive speed stabilization occurs 700 mil l iseconds after the drive motor is started.

2. Subsequent to any read/write operation, the positioner must be allowed to sett le. Thisrequires 18 milliseconds maximum after the last step pulse is initiated, i.e., 3 millisecondsfor the step motion and 15 mill iseconds for settl ing.

3. The foregoing operations can be overlapped, if required.

Figure 1-4 illustrates the timing diagram for a write operation. At t = 0, when the unit is ready,the write gate interface line goes true. This enables the write current source. Write current isswitched via the write current switch interface line to a lower value by the user's controller atTrack 43.

1-10

The Trim Erase control goes true 190 microseconds after the Write Enable interface linesince the trim erase gaps are behind the read/write gap. It should be noted that this value isoptimized between the requirements at Track 00 and at Track 76, so that the effect of the trimerase gaps on previous information is minimized.

Figure 1-4 shows the information on the write data interface line and the output of the writewaveform generator, which toggles on the leading edge of every write data pulse.

A maximum of 4 microseconds between write gate going true and the first write data pulse isonly required if faithful reproduction of the first write data transition is signifcant.

At the end of recording, at least one additional pulse on the write data line must be insertedafter the last significant write data pulse to avoid excessive peak shift effects.

NOTE 1

I

NOTE 2WRITE GATE

190 u sec

I~5 0 u sec~

ITRIM E:RASE

INTERNAL WRITEBUSY I

WRITE DATA

I INOTE 2 I

WRITEWAVEFORMGENERATOR I

I I

WRITE CURRENT - NOTE 3

NOTE 4Q1=0

NOTES: 1, T = 0 700 MILLISECONDS AFTER DRIVE MOTORSTARTS OR 20 MILLISECONDS AFTER LAST STEPPULSE, WHICHEVER IS THE LATEST TIME.

3. 1 0 MA PEAK TO PEAK, TRACK 0 TOTRACK 42; 7.5 MA PEAK TO PEAKTRACK 43 TO TRACK 77.

2. UNS YCHRONIZED 4. 2 USEC MINIMUM4 USEC MAXIMUM

Figure 1-4Write Operation Timing Diagram

The duration of a write operation is from the true going edge of write gate to the false going edge oferase. This is indicated by the internal write busy waveform shown (see Figure 1-4).The Read electronics consist of:

1, Read Switch/Side Select

2. Read Preamplifier

3. Filter

4. Differentiatior

5. Time Domain Filter and Digitizer

The read switch is used to isolate the read amplifier from the voltage excursion across the headduring a write operation. The side select is used to enable one of the read/write/erase heads.

The drive must be in a ready condition before reading can begin. As with the data recording operation,this ready condit ion must be es tabl ished by the user system. ln addit ion to the requirementsestablished in this section, a period of 100 microseconds is necessary after a trim erase operationoccurs to allow the read amplifier to settle after the transient caused by the read switch returning tothe read mode.

1-11

The output signal from the read/write head is amplified by a read preamplifier and filtered by a lowpass linear phase filter to remove noise (see Figure 1-5). The linear output from the filter is passed tothe differentiator, which generates a wave form whose zero crossovers correspond to the peaks of theRead signal. This signal is then fed to the zero crossing detector and digitizer.

II IIII

I I

I I

LINEAR OUTPUT FROM FILTER I

I I I

OUTPUT FROM DIFFERENTIATOR

I II

IIII

DIFFERENTIAL DROOP

READ DATA INTERFACE

I I II I

I f II I II > I

I = o

Figure 1-5Read Timing Diagram

Note

T = 0 is defined as 250 milliseconds after drive motor starts, or 20 milliseconds after a stepcommand, or 100 microseconds after termination of write busy, whichever is the latest time.

The zero crossover detector and digit izer circuitry generate a 200 nanosecond read data pulse,corresponding to each peak of the read signal. The composite read data signal is sent to the usersystem via the read data interface line.

1.16 I NTER FACE ELECTRONICS

All interface signals are TTL compatible. Logic true (low) is +0.4 volt maximum, logic false (high) is+2.4 volts minimum. The maximum interface cable length is ten feet. It is recommended that theinterface cable be flat ribbon cable that has a characteristic impedence of 100 ohms.

1.16.1 Inte r face Connector Pin Assignments, P13

The interface connector pin assignments, P13, are listed in Table 1-3.

1.16.2 Pow e r Connector Pin Assignments

The power connector pin assignments are listed in Table 1-4.

1-12

TABLE 1-3

I N TE R FAC E CO N N ECTO R P I N ASS I G NM E N TS

Ground Pin Number

1

3 52 4 6

810

12

14

1618

20

2224

2628

30

32

3436

3840

4244

46

48

50

~si nal

Write Current SwitchMotor Off Control 1Motor Off Control 2

Motor Off Control 3Two Sided (option) (Model TM848-2 only)

Disk Change (option)Side Select (Model TM848-2 only)Activity Indicator (option)

Head Load

Index

ReadyMotor Off Control 4

Drive Select 1 (Side Select Option, TM848-2 only)Drive Select 2 (Side Select Option, TM848-2 only)

Drive Select 3 (Side Select Option, TM848-2 only)

Drive Select 4 (Side Select Option, TM848-2 only)Direction Select (Side Select Option, TM848-2 only)

Step

Write DataWrite Gate

Track 00Write Protect

Read Data

Alternate I/OAlternate I/O

7

911

13'15

'17

19.'21

,'23

.'25

27

29

31

3335

3739

41

43

45

47

49

TABLE 1-4

POWER CONNECTOR PIN ASSIGNMENTS

S u I Vo l t a e

24V D. C.ReturnReturnReturn

5V D. C.

Pin

1.17 TERM IN ATED LINES

1.17.1 Inp u t L ine Terminations From Removable Resistor Pack

The drive has the capability of terminating the following input lines:

1. Write Current Switch

2. Write Data

3. Write Gate

4. Side Select (TM848-2 only)

5. Direction

6. Step

7. Head Load

These input l ines are individually terminated through a 150 ohm resistor pack that is installed in thedip socket located at integrated circuit location RP1. In a single-drive system, this resistor packshould be installed to provide the proper terminations. In a multiple-drive system, only the last driveon the interface is to be terminated. All other drives on the interface must have the resistor packremoved (see Figure 1-6).

1.17.2 Driv e Se lect

The Select lines provide a means of selecting and deselecting a drive. These four lines- DS1 throughDS4-allow independent selection of up to four drives attached to the controller.

When the s ignal logic level is t rue ( low), the dr ive e lectronics are act ivated and the d r ive isconditioned to respond to Step or to Read/Write commands. When the signal logic level is false (high),the input control lines and the output status lines are disabled.

The drive select address is determined by a movable shorting plug installed on the circuit board.Select lines one through four provide a means of daisy chaining a maximum of four drives to acontroller. Only one line can be true (low) at a time. An undefined operation might result if two or more unitsare assigned the same address or if two or more select lines are in the true (low) state simultaneously (seeFigure 1-7). A select line must remain stable in the true (low) state until the execution if a Step orRead/Write command is completed.

1.17.3 Pro g ram Shunt

The program shunt is AMP Part Number 435704-8. The program shunt positions are programmed bycutting the particular shunt. The program shunt is installed in a dip socket. At the user's option, theprogram shunt may be removed and replaced by a dip switch. Pins 8 and 9 of the program shunt arenot used. See Table 1-5 for a listing of the program shunts.

1-14

P7 TP2 2S ooM3

OM4TP1 00Rl

P4

00 DS ' I TP30 0 0 0 0 1b 0 00 DS2

2bo oo DS3U3 P5

3b o4b 0

oo DS4 00 RM

MC3

TP5 0000Q (0IZ 0TP4 PT6

MC200$ MC1

0

0C

MC4 0

S2 0 O S 1

D o32

NP Oo Y

ALTERNATE TEST POINT INDEX TRIGGERING

RPIO~ Qas2

R133DSI

WPTP11 0 0 T P 12 Ml g

P13

50 TP 70

0TPS

o ODL

OTPS

OTP1000

3 M2

IL P6 P14P2 P3 P10 P1 P! I P12

Figure 1-6Circuit Board Assembly

D.C. POWER

MOTOR OFF

DRIVE SELECT

500 NSEC. MINIMUM

0.8 SEC MAXIMUM

OUTPUTS VALID

500 NSEC'MINIMUMDIRECTION

SELECT

1 USEC. MINIMUM1 USEC MINIMUMSTEP

1 USEC.

M I Nl MUM3 MILLISECONDS MINIMUM

SIDE SELECT

100 NSEC MINIMUM

WRITE GATE

4 USEC. MAXIMUMWRITE DATA

18 MSEC. MINIMUMVALI

READ DATA

100 USEC. MAXIMUM 550 USEC. MINIMUM

Figure 1-7General Control and Data Timing Requirements

1-16

1.18 D S A N D HL POWER SAVE OPTIONS

The drive is set upwith the HL option in. This stepper power from head load line option supplies powerto the stepper motor when the head load line goes low (true), which results in lower stand-by currentconsumption. As shipped from the factory, HL is installed but will remove power from the steppermotor when the dr ive is deselected. There should be a 20 mi l l isecond wait after a Drive Selectcommand is given in order to allow the step motor electronics to sett le.

The stepper power from drive select, DS option, allows the user to remove D. C. power from thestepper motor using drive select, which results in lower stand-by current consumption. This option isimplemented by installing DS, and cutting HL.

1.19 USER S E L ECTABLE OPTIONS

The description of user selectable options should be used in conjunction with the following list ofoptions that are available for model numbers TM848-1 and TM848-2 (see Table 1-5).

TABLE 1-5

OPTIONS

AS S H IPPEDTRACE

OPTION

Drive SelectSide Select Options using Drive SelectIn Use, Drive SelectIn Use, Head LoadReady Alternate Output PadRadial ReadyReady, ModifiedRadial IndexIndex, Alternate Output PadIn Use, Alternate Output PadDiskette Lever Lock Latch OptionDisk ChangeTwo-Sided Diskette InstalledStepper Power from Drive SelectStepper Power from Head Load LineHead Load Alternate Output PadRadial Head Load SignalRadial Head Load SignalRadial Head Load SignalInhibit Write When Write ProtectedAllow Write When Write ProtectedHead Side Select OptionsSpindle Motor Control OptionsMotor Control Select

DESIG NATOR

DS1-DS41 B-4B

Z

Y R

RRRMRl

C A B X

DDLDC2SDSHL

WPNP

S1-S3M1-M4

MC1-MC4

Shunt/PinLocations

U3, 6-11

U3, 1-16

U3, 7-10

U3, 2-15

U3, 3-14U3, 4-13U3, 5-12

Installed

DS1

X X X X

X X

X

M2, M4

NotInstalled

S2M1, M3

MC1

1-17

1.19.1 Dri v e Select DS1-DS4

This option allows the user to daisy chain up to four drives, and to enable one drive at at time.

Drive select is implemented by shorting one of the four connections, using a shorting plug. The drivecomes equipped from the factory with DS1 installed. All outputs are gated with drive select, as set-upat the factory.

1 .19.2 S id e Se lect Options Using Drive Select 1B-4B

This option allows the user to select the head to be used with drive select.

Side Select options are implemented by removing the shorting plug from the DS1-DS4 option pads,installing Pins 1 B-4B, and connecting the shorting plug to the desired 1 B-4B pins. S2 should be etchcut, and S3 installed (see Section 1.18).

1.19.3 In U s e F rom Drive Select (Z)

This option allows the user to enable the activity L. E. D. when the drive is selected.

In Use From Drive Select is factory installed.

1.19.4 In Us e F rom Head Load (Y)

This option allows the user to use the head load line to enable the Activity L. E. D.

In Use From Head Load is implemented by punching out Option Z between Pins 1 and 16 of U3. Ajumper must be installed at location Y.

1.19.5 Read y A l ternate Output Pad (R)

This low going signal is derived by gating the internal ready and drive select to give the controller atrue (low) ready status of the drive.

. The Ready Alternate Output Pad is factory installed.

1.19.6 R a d ial Ready (RR)

This option allows the user to monitor the ready status of all drives without selecting them. This optioncannot be used concurrently with individual motor control lines for each drive. (see Figure 1-8).

Radial Ready is implemented by punching out Option R between Pins 7 and 10 of U3, by etch cuttingRR, then by running a wire from U4, Pin 3 to the desired alternate output lines 4, 6, 8, and 24.

1-18

DREDv +PROGRAM SHUNT PINS 7-10 ARE OPENED

R14 47R4

I 0544 4 .. 4 IIEAAY~E I

SIDE 1

IN1 FF+

IREADY

DRSEL -I

L'502,

Oa 4 LAOK

I Ua

I/i'tlII

%5V

R99150

RR

M 2~

ETCH CUT RA7ilK~READSTATUS

TO USERCONTROLLER

i XMcc

Figure 1-8

Radial Ready Installation

Note

MC1 through MC4 cannot be used as radial motor control when using this option.

1.19.7 Rea d y , Modif ied (RM)

This option allows the drive to write on the upper surface of a single-sided diskette. It prevents thedrive from making Ready become false when the upper surface of a single-sided diskete is selected.To implement this option, connect a jumper at the RM pads.

1.19.8 Ra di a l Index (Rl)

This option uses the alternate I/O lines for radial index lines. This option allows the user to monitor theindex of each drive independent of drive select. This option cannot be used concurrently with radialready, or with independent motor control.

Radial Index is implemented by removing the shunt bridge at U3, Pins 6 and 11, by etch cutting radialindex, and by running a wire from U4, Pin 6, to the appropriate alternate I/O lines. If use of MC1 isdesired, interface l ine 20 may be used as one index l ine. In this case, the shunt pack, U3, 6-11,remains intact on one drive, (see Figure 1-9).

1-19

+5V

PROGRAM SHUNT PINS 6-10 ARE OPENED

DRSEL +

INDEX +

RI54.7 l4

54 V4RI

+5V

R99ISO/II

l~

I<~ q

~ M C '5

~ i~

RADIAL INDEXSTATUS TOUSERCONTROLLER

+ C4

Figure 1-9Radial Index Installation

1.19.9 Inde x A l ternate Output Pad (I)

The internal index pulse is gated with drive select to give a low true signal at Pad I. This option shouldbe left connected for the controller to receive the index pulse. See Radial Index for other uses of thisline.

The Index Alternate Output Pad option is factory installed.

1.19.10 In U se Alternate Output Pad (D)

This line may be used to latch a lever lock solenoid, which is an optional feature. A low(true) commandis sent by the controller to Pin 16 of interface connector P13. Then this signal is used with drive selectto latch the locking solenoid by pulsing drive select with IN USE low. The solenoid is unlatched whendrive select is pulsed and 5I USE is high.

To implement this option, locate option pads D and DL. Install jumpers at these locations.

1.19.11 D i skette Lever Lock Latch Option (DL)

This option is used in conjunction with in use, alternate output pad.

To implement this option, locate option pads D and DL. Install jumpers at these locations(see Section1.1 8).

1.19.12 D isk Change (DC)

This output is used to indicate to the controller that a disk change has been made. The internal signalis gated with drive select. When the lever is opened, the disk change line goes low(true), and stays lowuntil the trailing edge of the next drive select.

1.19.13 Tw o -Sided Diskette Installed 2S

When a two-sided diskette is installed, internal circuitry gates this signal with drive select, and sendsa low (true) signal to the controller, which means that a double-sided diskette is installed (index holetwo is present).

The Two-Sided Diskette Installed option is factory installed.

1-20

1.19.14 Stepper Power From Drive Select (DS)

This option allows the user to remove D. C. power from the stepper motor using drive select, whichresults in lower stand-by current consumption.

The Stepper Power From Drive Select option is implemented by installing DS, and cutting HL.

1.19.15 Stepper Power From Head Load Line (HL)

This option supplies power to the stepper motor when the head load line goes low(true). This resultsin lower stand-by current consumption.

This option is factory installed. DS must be removed for proper operation.

1.19.16 H e ad Load Alternate Output Pad Option C

This option allows the user to load and unload the head load solenoid (optional) and, along with the HLand Y options, enables the stepper motor and lights the Activity L. E. D., respectively. Head load isaccomplished by connecting both option pads C located near interface connector P13.

1.19.17 R a d ial Head Load Signal, Options A, B, and X

By selection of the appropriate combination of the A, B, or X jumper, the user can use either DriveSelect or Head Load to activate the Activity L. E. D. and Lever Lock Solenoid option (see Figure 1-10).

R4 DslDSI 2 1 IB

052 2 S

Clss 30

Dsa [~P

D'SZ 4L'S04

35

ZBDS'S

054

+C7

$4.7VIP

L'300

Ul

Nl 15

US QZat,

STRE OI +

HEADLOADSOLELIOIDtoUl 2

1412,

9 5 D lit +SIDEl'314 Dl I

LSDZ

U5L'304

VISA Cls

USI - . I

4 L S D D

15295 2100

Ol ACTH/ITT1414

U'\ ls 5rl 4LS04

3HLOFF HLL

45 LSDB

IIS HEAD LEAD F.R lzl

2D Q

+Z4 79

UICo2

U 2'SUlo 2 754Co?. SOENDIO

NIOFFHEAD IDADI

lEVER IOCK LATCHl

02

UC(

L DO

U1527

IKlCiAZ,

Figure 1-10Radial Head Load Signal

1.19.18 I n h ibit Write When Write Protected (WP)

This option is used to lock out the write gate when a write protected diskette is installed.Inhibit Write When Write Protected is factory installed.

1.19.19 A l low Write When Write Protected (NP)

This option allows the controller to write on any diskette, whether or not is is write protected.

1-21

Note

This option does not stop the write protect signal from being sent on the interface line.This option is implemented by cutting WP, and by installing NP.

1.19.20 Head Side Select Options S1-83

This option allows heads to be selected by side select, drive select, or the direction control signal. Thedrive comes with side select, S2, installed.

To use the drive select line to enable the heads, cut S2 and install S3 along with the proper 1B-4Bjumper that is used with S3 (see 1B-4B). For head selection using Direction Select, cut S2, and installS1.

1 .19.21 S p indle Motor Control Options M1-M4

M1 is used to enable the motor off delay t imer. When this jumper is installed, the drive motor isenabled and disabled by either the drive select (M3) or head load (M4) commands. A 20-second turnturn off delay of the spindle motor is activated on the trailing edge of the controlling signal.

M2 is used for radial motor control independent of the motor control functions installed with M1, M3,and M4.

M2 should be in if the user wishes to enable the drive motor continuously or to use the radial motor online MC1-MC4.

M3 is used to control the drive motor using drive select. When the drive select line goes low (true), thedrive motor comes up to speed in less then 500 milliseconds and becomes ready in less than 700milliseconds. After the dr ive select l ine goes false (high), the motor wil l run for 20 seconds. Toimplement this option, install a jumper at location M3. For correct operation of M3, remove M4.

M4 is used to start the drive motor using the head load interface lines. When the head load line goeslow (true), the drive motor comes up to speed in less than 500 milliseconds and becomes ready in lessthan 700 milliseconds. After the head load line goes high (false), the motor will run for 20 seconds. Toimplement this option, remove M3 for correct operation of option M4.

1.19.22 Mot o r Control Select Options MC1-MC4

This option is used if the drive motor is to be enabled independent of drive select or head select. Whenthese lines are low(true), the motor is off. The drive comes without this option installed. This optiondoes not operate the t ime out delay circuit.

To implement this option that controls the drive motor using an MCx line, install the appropriate MC1MC4 jumper. When using this option, M2 must be installed. If the motor turn off delay is desired, thedelay can be triggered by Drive Select or Head Load commands, when used in conjunction with M3 orM4.

1-22

SECTION II

MAINTENANCE CHECKS AND ADJUSTMENTS

2. INTRO DUGTI ON

This section is for the use of the OEM Repair Department. It contains checks and adjustments that areused during the normal life of the drive.

Before applying power to the drive or doing any checks or adjustments, visually inspect the drive toensure that it has no missing or broken parts.

The following equipment is required for checks and adjustments:

1. A dual-channel, wideband oscilloscope: T e k t ronix 465 or equivalent

2. An exerciser or software routine capable of stepping the drive to any track, selecting theupper or lower head, and writing a 1F, all zeros if FM,or a 2F, all ones if FM, pattern on the disk.

3. A Phillips screwdriver

4. A set of Allen wrenches

5. A flat blade screwdriver

6. A blank diskette

7. An alignment diskette: D y san P/N 360/2A or equivalent

8. Integrated circuit dip clips, 14 and 16 pin

SPINDLE DRIVE MOTOR CHECKS AND ADJUSTMENTS2.1

The long-term drive motor speed adjustment ensures that the motor's speed is within the range oftolerance specified. The motor speed specification is 360 RPM + 1.25 percent.

2.1.1. Lo ng - Term Drive Motor Speed Checks and Adjustments

A. Preliminary checks required:

Verify power: +24V D. C. +10 percent+5V D. C. ~ 5 percent

B. Apply power to the drive.

C. Activate the drive motor on the interface line.

D. Insert a work diskette.

2-1

E. Set up the oscilloscope, as follows:

Voltage: 2 volts per division

Time Per Division: 20 milliseconds

Trigger: N e gat ive, Channel A, R33

Note

For the TM848-1 single-sided drive, trigger off of R33. For the TM848-2 double-sided drive,trigger off of Test Point 12, with the exception of azimuth, which must be triggered off of R33(see Figure 2-1).

M3

DCOO 0 M42SOO

00Rl

00 DSIob DS2

Ib 0

2b 0 OODS33b 0

OODS4 00 RM

4b 0f

TP40 0 0

TP5

MC3

000014 CbIX O

PTS

MC200 3MCI

0

S 2 000 5 10 0 S2

C 0

MC4 o

R33OO Y

ALTERNATE TEST POINT, INDEX TRIGGERING

NP

00 DS2Ds1

WPM IIITPII OQO P12

50 TP T OTPS

8 M20

TPS

OTPIO

0 DL IZ00

PS P14P2 P3 PI O PI PI I P 12

Figure 2-1Circuit Board Assembly

F. Adjust R133 until a reading of 166.667 milliseconds is achieved from leading edge to leadingedge of the index pulses.

G. If the drive motor's speed cannot be adjusted, see Section IV, Troubleshooting Guide.

2.2 CATS EYE ALIGNMENT CHECK AND ADJUSTMENT

The Cats Eye (C. E.) alignment procedure locates the read/write head at the oroper radial distancefrom the hub center line, ensuring that the track location is accurate(seeFigure 2-2). This adjustmentis necessary only after servicing or if diskette interchange problems are suspected.

2-2

HUB CENTER LINE

TRACK 0

TRACK 38

TRACK 76

Figure 2-2Hub Center Line and Track Locations

2-3

2.2.1 Cat s Eye Alignment Check

A. Set up an oscilloscope, as follows:

Channel A;

Channel B:

Test Point 2 alternate is Test Point 4 on R30

Test Point 3 alternate is Test Point 5 on R29

Test Point 1Ground

Read Differentially: A plus B, B inverted

Time Base:

External Trigger:

20 milliseconds per division

Test Point 11, negative trigger, for single-sided drives. Test Point12„negative trigger, for double-sided drives. R33 (end closest toDS2), negative trigger, is an alternate test point for both single- anddouble-sided drives.

B. Apply power to the drive.

Note

The Track 38 radius is 2.8207 2.0020. Other track locations are computed based upon 48TPI.

C. Select the drive at the interface.

D. Insert the alignment diskette into the drive.

E. Select Head 00, the lower head.

F. Seek to and observe Track 38 for Cats Eye alignment of the lower head.

G. Adjust the oscilloscope to observe a Cats Eye pattern (see Figure 2-3).

Equal amplitude.Lobes shown at 100percent on Track 38.

Time Scale: 20 ms

Figure 2-3Cats Eye Pattern

2-4

H. Verify that the smaller of the two Cats Eye lobes is not less than 75 percent in amplitude ofthe other one. The calculation is: am p of smaller lobe

amp o arger o e

I. Step the drive to Track 00, then, step it back to Track 38.

J. Reverify the Cats Eye pattern.

K. Step the drive to Track 76; then, step it back to Track 38.

L. Reverify the Cats Eye pattern.

M. On double-headed drives, select the upper head (Head 01) and repeat Steps F through L.

N. If any of the checks listed above does not meet the condit ions stated in Step H, the headcarriage must be adjusted.

HEAD CARRIAGE ADJUSTMENT2.3

A. Turn the two pos it ion retaining screws that st raddle the ny lon adjustment cam locatedbeneath the drive until the cam can be moved (see Figure 2-4).

POSITION RETAINING SCREWS (2)

O

OG )'

popIs

0 0

'0ADJUSTMENT CAM

Figure 2-4

Head Module Retaining and Cam Screws

B. Observe the Cats Eye pattern from the head that is farthest out of alignment.

C. Using a flat blade screwdriver, turn the adjustment cam until one Cats Eye lobe is within 75percent of the amplitude of the other lobe.

Note

Check the upper and lower heads on double-sided drives (see Section 2.2.1, "F" through"L" on upper head).

D. Tighten the two positioner retaining screws (see Figure 2-4).

2-5

E. Reverify the Cats Eye alignment (see Section 2.2.1).

2.4 INDEX S E N SOR CHECKS AND ADJUSTMENTS

The index adjustment changes the time period from the index pulse to the start of the data. Theadjustment should be checked after the drive has been aligned (see Section 2.1.1) or when disketteinterchange errors are suspected.

2.4.1 Index - to-Data Burst Check

A. Apply power to the drive.

B. Select the drive.

C. Check the spindle speed of the drive (see Section 2.1).

D. Set up an oscilloscope as follows:

Trigger:

Read Differentially:

Channel A:

Channel B:

Single-sided drives trigger onright lead of R33 (closest toDS2), negative edge; double-sideddrives trigger on Test Point 12,negative edge.

A plus B, B inverted

Test Point 2

Test Point 3

50 microseconds per divisionTime Base:

E. Insert an alignment diskette.

F. Seek to Track 1.

G. Select Head 00, the lower head.

H. Ensure that the index-to-data burst occurs at 200 microseconds k 100 microseconds fromthe leading edge of the index pulse (see Figure 2-5).

I. For double-sided drives, select Head 01 and repeat the steps above.

Note

Head 01 should meet the same specification.

J. If either Head 00 or Head 01 does not meet the specifications, adjust the index sensor (seeSection 2.4.2.).

2-6

Time Scale:50 usec perdivision

Figure 2-5Index-to-Data Burst

K. When both index measurements on a double-sided drive or the one index measurement on asingle-sided drive meet the specifications, see Section H, check the index-to-data burst onTrack 76.

L. On a double-sided drive, check Heads 01 and 00, the upper and lower heads.

Note

If any index measurement does not meet the specification, the index sensor must beadjusted (see Section 2.4.2).

2.4.2 In dex S e nsor Adjustment

A. Loosen the index sensor's retaining screw located on the underside of the chassis (seeFigure 2-6).

o o

INDEX SENSORRETAINING SCREW

0 0

6' -0-~e(o

J

Figure 2-6Index Sensor's Retaining Screw and Adjustment

2-7

B. Adjust the index sensor with a flat blade screwdriver until the index-to-data burst occurs 200microseconds + 100 microseconds from the leading edge of the index pulse.

C. Tighten the index sensor's retaining screw.

D. Reverify the index-to-data bursts (see Section 2.3.1).

2.4.3 Index P u lse Width Check

The index pulse width is nonadjustable. If the index pulse width is not within specifications, replacethe Index Sensor Assembly.

A. Set up an oscilloscope as follows:

Channel A:

Ground:

To appropriate index test point, seeSection 2, Item Number 1.

Test Point 1

.5 millisecond per division

2 volts per division

Negative leading edge of Channel A,appropriate test point.

Time Base:

Voltage:

Trigger:

B. Ensure that the negative going pulse width is between 1.0 and 2.3 milliseconds(see Figure 27).

1.8 to 2.3 milliseconds

Figure 2-7Negative Going Pulse Width

2.5 TRACK 0 0 SENSOR CHECK AND ADJUSTMENT

The Track 00 sensor provides a signal that identifies Track 00 to the logic electronics. A Track 00 signal issent to the controller on Pin 20 of the interface.

A. Apply power to the drive.

B. Load an alignment diskette into the drive.

C. Step the carriage to the radial alignment track, Track 38 (see Section 2.2).

2-8

D. Confirm the position by observing the Cats Eye pattern.

E. Attach Channel A to Test Point 10.

F. Restore the carriage to Track 00, and ensure that the Track 00 L. E. D. on the exerciser turnson.

G. Seek to Track 1, and ensure that the signal at Test Point 10 is high.

H. Seek to Track 2, and ensure that this line is low or in transition.

I. Seek to Track 3, and ensure that this line is low.

J. If the signal is incorrect, restore to Track 00 with the oscilloscope attached as above.

K. Seek out to Track 2, and loosen the two retaining screws that hold the Track 00 sensor (seeFigure 2-8).

TRACK 00 SENSOR

+I

P2 PS PlRETAINING SCREWS

0o

Figure 2-8Track 00 Sensor

L Push the sensor toward the back of the drive, and slowly push it forward until the signal on theoscilloscope just goes low (true).

M. Tighten the retaining screws, and repeat Steps E through I.

N. Verify the adjustment.

AMPLITUDE CHECK2.6

The amplitude test checks the necessary read, channel amplifier/differential output voltage.

A. Restore to Track 00

B. Insert a work diskette and write a 2F, all ones, pattern on the lower head.

2-9

C. Connect an oscilloscope to Test Points 4 and 5, using Test Point 1 as a ground.

D. Set up an oscilloscope as follows:

Channel A:Channel B:Both Channels:

Test Point 4, 1 volt per divisionTest Point 5, 1 volt per divisionA. C. coupled, Channels A and B added,Channel B inverted50 milliseconds per division,synchronize internally on Channel A or BAutomatic

Time Base:

Trigger:

E. The minimum amplitude displayed on the scope should be no less than three (3) volts peak-topeak at any point

F. Reverify the measurement with another work diskette.

G. Check the upper and lower head, if applicable.

H. If the amplitude is less than the specification, inspect the heads to ensure they are notcontaminated.

I. Clean the heads with a cleaning diskette if they are contaminated.

J. Replace the circuit board if cleaning does not improve the amplitude.

K. If replacing the circuit board does not correct the amplitude, replace the Head CarriageAssembly.

2.7 AZIMUT H CHECK

Azimuth is the angle of the heads with respect to the track at the point of the read/write gap. Azimuth ismeasured in minutes (one minute = 1/60 degree).

A. Set up an oscilloscope as follows:

Channel A: Test Point 2, 100 mV per division

Channel B: Test Point 3, 100 mV per division

Ground:

Both Channels: A. C. coupled, Channels A and B added,

Test Point 1

Time Base:

Channel B inverted

1 miilisecond or as required to displaythe pulse groups

Leading edge of appropriate test point(see Section 2, Item Number 1)

Trigger:

B. Insert an alignment diskette.

C. Step the drive to Track 76.

D. Observe the following pattern. Figure 2-9 depicts an optimum head alignment of zero minutes ofazimuth error. This means that the Head Carriage Assembly is perpendicular to the track beingread, Track 76. Bursts 1 and 4 are of equal amplitude; Bursts 2 and 3 are of equal amplitude.

2-10

Note

Measure the azimuth burst. Ensure that Burst 1is less than or equal to Burst 2, and that Burst4 is less than or equal to Burst 3.

1 2 3 4

Figure 2-9

Optimum Head Azimuth Al ignment

E. Figure 2-10 depicts an azimuth of exactly minus 9, 12, or 18 minutes, depending uponthe manufacturer of the diskette used. This is the lower limit of allowable azimuth error.Bursts 1 and 2 are of equal amplitude. If this signal is observed, the Cats Eye alignmentshould be checked prior to any corrective action.

3 '

Figure 2-10Head Azimuth of Acceptable Lower Limits

F. Figure 2-11 depicts an alignment of exactly plus 9, 12, or 18 minutes, depending uponthe manufacturer of the diskette used. Bursts 3 and 4 are of equal amplitude. This is theupper limit of allowable azimuth error. If this signal is observed, the Cats Eye alignmentshould be checked prior to any corrective action.

G. After the lower head has been checked, switch to read on the upper head and observethe azimuth pattern. Both the upper and lower heads should be within the specification.

2-1 1

3 4

Figure 2-11Head Azimuth Alignment of Acceptable Upper Limits

Note

The head's azimuth is not adjustable. It is suggestedthat the drive be sent to an authorized repaircenter or a new Head assembly be installed. In the lattercase, all previous adjustments should be made again.

2.8 LOAD A R M A DJUSTMENT

This adjustment is made to ensure proper loading of the head when the diskette is engaged (seeFigure 2-12).

A. Insert a work diskette into the drive.

B. Turn the diskette lever to load the disk, and seek to Track 00. There should be a space of.015inch minimum between the head load arm and the load plate.

C. Seek to Track 76, and ensure that a space of.015 inch minimum remains between the headload arm and the load arm.

D. Adjust the screw located behind the head load cam until the foam just touches the platen.

E. Insert a work diskette and ensure that there is adequate space between the upper head andthe diskette.

F. The upper head should not hit the diskette when inserting and ejecting it.

ADJUSTMENT SCREW

LOADING CAM

LOAD ARM

.015 INCH MINIMUM

HEAD ASSEMBLY

FOAM

PLATEN

Figure 2-12Load Arm Adjustment, Front View

2-1 2

SECTION I I I

PRINTED CIRCUIT BOARD OPERATION

INTRODUCTION

This section contains the interface description and the circuit board theory of operations for theTM848 familyof disk drives. In addition, Sections 3.1 and 3.2 contain schematic diagrams of thecircuit boards Installed in the drive.

3.1 PH YS ICAL DESCRIPTION OF THE CIRCUIT BOARD

The printed circuit board is approzimately 12.50-inches long by 5.25-inches wide. Figure 3-1contains an illustration of the placement of test points and connectors.

M32SOODCOO 0 M4

TP200Rl

00 DSIIb 0 00 DS2

2b 0 ooDS335 0 00 DS4 RM045 0

MC3

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0

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32

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50 TPT OTPS

OTPIO

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M200IZ P6 P14

TPS

Figure 3-1Printed Circuit Board

3.2 IN TER FACE ELECTRONICS SPECIFICATIONS

All interface signals are TTL compatible. Logic true (low) is+0.4 volt minimum. Figure 3-2 illustratesthe interface configuration. The maximum interface cable length is ten feet.

+ SV

I

IIIIT

160 OHMS

I TWISTED PAIR 74LSD4 DR EQUIVALENT

4 TRUE

I II I

I ILTl16 DR EQUIVALENTgIIIIIII

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II T RA NSMISSION LINEIIIIIIII RECEIVERIIIII

Figure 3-2Interface Configuration

It is recommended that the interface cable be flat ribbon cable, with a characteristic impedance of100 ohms.

Interface connector pin assignments are given in Table 3-1.

3.3 IN P UT CONTROL LINES

A. DS1-DS4, Select Lines

Functional Description

The select lines (see Figure 3-3) provide a means of selecting and deselecting a drive. These fourlines, DS1 through DS4, select one of the four drives attached to the controller. When the signal logiclevel is true (low), the drive electronics are activated, and the drive is conditioned to respond to Step orRead/Write commands. When the logic level is false (high), the input control lines and output statuslines are disabled.

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Figure 3-3Select Lines Schematic Diagram

A select line must remain stable in the true (low) state until after a Step or Read/Write command hasbeen executed.

The drive select address (1-4) is determined by shorting plugs on the circuit board. Select lines 1through 4 provide a means of daisy chaining a maximum of four drives to a controller. Only one linecan be true (low) at a time. An undefined operation might result if two or more units are assigned thesame address or if two or more select lines are in the true (low) state simultaneously.

Circuit Description

An 150-ohm resistor holds the output of the appropriate Select line high (false) until the line is drivenlow(true). Then, the Select signal is gated through U1 and U5 to derive the signal DRSEL+. DRSEL+is used to gate all I/O Port, ensuring that only one drive's data is present on the interface at a time.Writing and stepping are also gated by the signal DRSEL+. This signal is inverted by U13, thenbuffered by U15 to drive the Activity L. E. D., which is located on the front panel. Option Z is factoryinstalled. It should be installed for the Activity L. E. D. to operate with Drive Select.

B. MOTOR ON, Drive Motor Enable

3-2

TABLE 3-1 •

DRIVE INTERFACE LINES AND PIN CONNECTORS

Ground Pin Number

1

3 5 7 9

2

4 6

810

1214

16

1820

22

2426

28

3032

34

3638

40

4244

4648

50

Signal

Write Current SwitchMotor Off Control 1

Motor Off Control 2

Motor Off Control 3Two Sided (Strappable) (Model TM848-2 only)Disk Change (Strappable)Side Select (Model TM848-2 only)Activity Indicator (Strappable)Head Load LineIndex

ReadyMotor Off Control 4Drive Select 1 (Side Select Option, TM848-2 only)

Drive Select 2 (Side Select Option, TM848-2 only)

Drive Select 3 (Side Select Option, TM848-2 only)Drive Select 4 (Side Select Option, TM848-2 only)

Direction Select (Side Select Option, TM848-2 only)

StepWrite Data

Write Gate

Track 00Write Protect

Read DataAlternate I/O

Alternate I/O

1113

15

1719

21

2325

27

2931

33

3537

39

4143

4547

49

3-3


The TM848 has a D. C. brushless motor that can be enabled in three ways:

1. By using the four radial Motor Control lines, MC1 through MC4.

2. By the Head Load line using shorting plug M4. Using this line enables all drives' Motor Onlines.

3. By Drive Select, using shorting plug M3.

The Motor Control lines, MC1 through MC4, are true (low) signals that turn the motor off. Shorting plugM2 must be installed for these control lines to operate.

When a Motor Control line is false (high), the drive motor accelerates to its operational speed in lessthen 500 milliseconds. This keeps the spindle rotating at a constant speed of 360 RPM. When theMotor Control line is true (low) the motor coasts to a stop.

When using Head Load to enable the drive motor, M4 must be installed. All of the motors are enabledwhen the Head Load line goes true (low). M1 should be installed if a motor turn off delay is desired.See Section 1.19.21 for an additional description of this circuit.

When a Drive Select line is to be used for Motor Enable, M3 must be installed. This enables the drivemotor when the Select l ine goes low.

Circuit Description

When the motor is enabled by any of the above, U35, Pin 6, floats high, allowing the speed control U41to start the drive motor. Two Hall Effect transducers in the motor, supply the necessary feedbacksignals for proper speed regulation. When U35-6 goes high, the output of U41, Pin 6, turns on Q21,which in turn applies a varying voltage to Q20 that regulates the amount of current through Q20, andthe motor driver transistors Q1 through Q4. Transistors Q1 through Q4 are turned on by the gatedpulses derived from the conditioned outputs of the Hall Effect transducers. The conditioned output ofU38, Pin2, is subsequently conditioned by Gate U36, which acts as an edge trigger and pulse doubler.This signal is fed back to U41, Pins 2 and 3, which results in closed loop speed control. The drivemotor's rotational speed is approximately 2520 RPM, when adjusted, to give a spindle speed of 360RPM.

C. DIR STEP, Direction and Step Lines


When the drive is selected, a true (low) pulse with a time duration between 200 nanoseconds and 2milliseconds on the Step line initiates the track access motion. The direction of motion is determinedby the logic state of the Direction line when a Step pulse is issued. The motion is toward the center ofthe drive if the Direction line is in the true (low) state when a Step pulse is issued. The direction ofmotion is away from the center of the drive if the Direction line is in the false (high) state when a Steppulse is issued. To ensure proper positioning, the Direction line should be stable for a minimum of 100microseconds before the trailing edge of the corresponding Step pulse. The Direction line shouldalso remain stable until 100 microseconds after the trailing edge of the Step pulse. The accessmotion is initiated on the trailing edge of the Step pulse.

When the carriage is positioned at Track 00 and the stepper motor is at Phase 0, the signal at Pin 42 ofP13 goes true (low), indicating that Track 00 has been reached.

When stepping in or out, Test Point 8 is a high going pulse for each step pulse issued.

3-4

Circuit Description

The Direction line comes in on Pin 34 of the interface connector. A high signal directs the step logic tostep toward Track 00. A low signal directs the step logic to step toward a higher numbered track.

The direction line sets the proper phase to the exclusive OR gates of U9.

TABLE 3-2

STEPPER LOGIC TRUTH TABLE

Step Out Toward Track 00 Step In Toward The

Pin No.U21-9U21-8U21-5U21-6

Phase0 3 2 1 0 Pin No. 0 10 1 1 0 0 0 01 0 0 1 1 1 10 0 1 1 0 0 11 1 0 0 1 1 0

Upper Tracks

Phase2 3 01 1 00 0 11 0 00 1 1

U21-9U21-8U21-5U21-6

The step pulses come in at Pin 36 of the interface connector. They are buffered by U22 and gated atU14 by the unit select, and the Not Write signal. The step pulses then go to the C inputs of the two flipflops at U21. The direction of the step, hence the selection of the flip flop to be toggled, is done by thetwo exclusive OR gates of U9. These gates are controlled by the step direction line and by the state ofthe two flip flop outputs.

The POR- (Power On Reset) signal resets the two flip' flops to Phase 0 after a Power On.

The output of the two flip flops drives the stepper motor through the drivers of U39, U40, and U12. Thediodes, CR2-9, are for voltage spike el imination. The current through the stepper motor coils isreversed sequentially, one at a time.

D. WAX"GITE


When the Write Gate signal is true (low), the write electronics are prepared for writing data (readelectronics disabled). This signal turns on the write current in the read/write head. Data is writtenunder control of the Write Data input line. It is necessary for the Write Gate interface line to go lowbefore the first Write Data pulse. However, the separation between the leading edge of Write Gateand the first significant Write Data pulse should not be less than two microseconds and not greaterthan four microseconds. The same restrictions exist for the relationship between the last Write Datapulse and the termination of the Write Gate signal. When the Write Gate line goes false (high), thetrim erase will stay on for 550 microseconds (see Trim Erase, page 3-7).

When a w r i te-protected d iskette i s i ns tal led in th e d r ive, the w r i te e lect ronics are d isabled,irrespective of the state of the Write Gate l ine. Check the l ist of opt ions (see Section 1.19) forexceptions and further discussion of write protect options. Stepping is also disabled by a true (low)Write Gate.

Tendon Corporation recommends that the controller wait one millisecond after the WWRWATE goeshigh (false) before any step pulses are sent to the drive.

Circuit Descri t ion

A low (true) WRT GATE signal is applied to Pin 40 of the interface connector P13. This signal is

3-5

inverted and gated with Write Protect and Drive Select to enable U23, U30, and Q13. Transistors Q13and Q12 are write current switches. Q13 and Q12 are on in parallel when the low Write Currentinterface is high (false). This results in a write current of 10 milliamps. When the low Write Current linegoes low (true), transistor Q12 turns off, and the current decreases to 7 milliamps. R52 and R51determine the amount of write current supplied to the head. The network CR18, CR19, CR20, R80and R81 is a power-loss write disable. If a sudden voltage loss occurs, transistor Q14 turns off,disabling the write current.

E. WRT DATA


When the drive is selected, the write data line provides the bit-serial Write Data pulses that control theswitching of the write current in the heads. The write electronics must be conditioned for writing bythe Write Gate line.

For each high-to-low transition on the WRT DATA line, a flux change is produced at the head write gap.This causes a flux change to be stored on the diskette (see Figure 3-4).

N INTERNAL WRITE BUSYSELECT

LOGIC

SIDESELECT

READ/WRITECOILS

WRITEDRIVER I

WRITEDATA

TRIGGER

WRITEDRIVER 2

ERASE

COIL

NWRITE GATE

N WRITE PROTECT

UNIT SELECTIN WRITE)

WRITECURRENTSOURCE

ERASEDELAY

LOGIC

ERASECURRENTSOURCE

IN INTERNAL ~ R E AD DISABLEWRITE BUSY)

Figure 3-4Write Data Circuit Block Diagram

When a double-frequency type encoding technique is used (in which data and clock form the combinedWrite Data signal), it is recommended that the repetition of the high-to-low transitions, when writingall zeros, be equal to the nominal data rate +0.1 percent. The repetition rate of the high-to-lowtransitions, when writing all ones, should be equal to twice the nominal data rate +0.1 percent. Thedata transfer rate for a 1F pattern is 250,000 Bits Per Second (BPS). The data transfer rate for a 2Fpattern is 500,000 BPS.

3-6

Circuit Description

Data is sent to the drive via interface Pin 38. This signal is inverted by U22, and is used to clock the Dflip flop U23. The outputs of U23 are inverted subsequently, and used to drive Q15 and Q17, whichdirect the write current to the correct winding.

F. TRIM ERASE


The TM848 uses a tunnel erase scheme to achieve trim erase, which is used to erase a guard bandaround the data tracks, allowing minor track offsets and minor misalignment without data errorsoccurring. The erase poles are staggered.036 inch behind the read/write poles. At a media rotationalspeed of 360 RPM, the tunnel erase method requires that the trim erase be delayed for 190microseconds afer the start of writing and that it be continued for 550 microseconds after the end ofwriting the data. The two one shots in U30 provide these delay time intervals.

When the write gate goes low, U30, Pin 9, (A input), is triggered and a high to low to high transition of190 us is generated. The write gate is also applied to U30 Pin 1 (A input). When the write data isapplied to the WRT DATA line, U23 condit ions the data which in turn generates the signal WRTTRAN+ (write transition+). This signal is then applied to U30 Pin 2, (B input) which is a positivetriggered input. This clock will retrigger this one shot continuously until the last transition of the WRTTRAN+ and WRT GATE — occurs. At this time, the one shot stays on for an additional 550 us. Theseoutputs (U30, Pins 12 and 13) are gated by U31 which is the trime erase gate. This output goes lowwhenever both inputs are high, causing the trim erase to be enabled (see Figure 3-5).

G. SIDE SELECT


SIDE SELECT can be generated three ways. See the option listing, Section 1.19, for this information.*

When the Side Select signal is low, Side 1 (the upper head) of the drive is selected for read/writeoperations. When this signal is high, Side 0 of the drive is selected (see Figure 3-6). The Side Selectsignal must be stable during an entire read or write operation. This signal is best implemented insynchronization with the Drive Select line signal.

Circuit Description

As shipped from the factory, the Side Select signal is received on Pin 14 of edge connector P13. Thissignal is received by U22, inverted, then inverted again by U13. The output of U13, Pin 10, generatesthe signal called Side 1 —.

The Side 1 — signal is applied to U13, Pin 9, and U24, Pin 13. The output of U13, Pin 8, is applied to U24,Pin 1. This output at Pin 2 of U24 is the opposite of U24, Pin 12. The resistor divider network sets upthe biasing voltages to turn on and turn off the head select transistor, Q18 or Q19. The head biasingvoltages seen across the collector resistors will be 5.2V D. C. when selecting a head for a readoperation, 12V D.C. during a write operation, and OV D. C. when the head is not selected. The emittervoltages on Q18 and Q19 will always be the opposite of each other, causing CTO or CT1 (center tap 0,center tap 1) to be selected.

3-7

WRT GATE

4us max.

WRT DATA

WRT TRAN +

(~ iso

U30, Pin 12Sec A, Q output

550us

U30, Pin 13Sec B, Q output

U31, Pin3Trim erase Source

Figure 3-5Trim Erase Diagram

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Figure 3-6Side Select Schematic Diagram

3.4 O U TPU T CONTROL LINES

A. INDEX/SECTOR


The Index signal is provided once cash revolution (166.667 milliseconds nominal) to indicate thebeginning of a track to the controller. The Index line remains in a low(true) state for the duration of theindex pulse. The duration of the Index pulse is nominally 2.0 milliseconds. Two index sensors aresupplied for use with single- or double-sided media.

The leading edge of an Index pulse is always used for timing to ensure diskette interchangeability

With a standard, soft-sectored diskette installed, the signal at R33 (see Figures 3-7 and 3-8) is a highgoing pulse, nominally 2.0 milliseconds in duration, every 166.667 milliseconds.

between drives.

Circuit Description

Light from the Index L. E. D. is used to drive the index sensor, which is applied to the inverting input ofU32. This signal is conditioned by U32, then inverted by U33. It is used to dr ive U26. Then theRespective index pulses are gated by U20, then with drive select by U4 to generate the signal index.U26 and the associated support integrated circuits U16 and U20 are configured to allow only theIndex 1 signal to be present on the interface when a two-hole diskette envelope is used.

When a double-sided diskette is installed, the signal IN1FF+ is generated and gated by U4 to enablethe output TWO SIDED.

B. Ready


Ready is used by the controller to ascertain the status of the drive. This signal is generated when thedrive motor is on, the diskette installed, and the drive is selected. The signal takes less than 700milliseconds to go true (low) from a motor start by Drive Select or Head Load (see Section 1.19.21).

Circuit Description

The index pulse is gated by U5, which in turn, triggers U17, a 220 millisecond retriggerable one shot.When the i ndex-to-index t ime becomes less t han 22 0 m i l l iseconds, the one s ho t b e comescontinuously enabled and generates the signal SPIN —.

This signal is gated with POR+, Power On Reset, to enable the two-revolution counters U18. Theoutput of U18, Pin 8, enables U6, whose output is gated with Drive Select to generate the signalready. Whenever the dr ive motor is d isabled, MTRON+ goes low, causing this sequence to berepeated when the motor is restarted.

C. Disk Change


E Ett . *been made.

3-1 0

Circuit Description

The disk change flip-flop, U10, is reset by OPEN- whenever the lever is in the open position. When thisoccurs, U10-6 is high, and a true disk change status is sent to the interface on Pin 12 from U4-11. Flipflop U10 is set on the trailing edge of drive select causing U10-6 to go low and setting the disk changestatus to the false state.

In actual use, this signal can be used by the host controller to determine that the diskette lever hasbeen opened since the end of the previous drive select operation.

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Figure 3-7Index Schematic Diagram

166.667ms

Figure 3-8Waveform at Test Point 11 or 12

Alternate Test Point, R33Soft Sectored Diskette Installed

D. TRK 00


When the drive is selected, the Track 00 interface signal indicates to the controller that the read/writehead is positioned at Track 00. The Track 00 signal remains true (low) until the head is moved awayfrom Track 00. The Track 00 sensor is activated internally between Tracks 2 and 3.

Interface Pin 42 (see Figure 3-9) is true(low) when the carriage is positioned at Track 00 and the stepmotor is at Phase 0.

3-1 1

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Figure 3-9Track 00 Schematic Diagram

Circuit Description

When the read/write carriage is restored to Track 00, a tab on the carriage blocks light from the Track00 L. E. D., turning off the Track 00 sensor transistor. This enables the inverting input of U32, a quadcomparator causing U32, Pin 13, to go high.

This signal is gated with Phase 0 of the step circuit and with drive select to generate the signal TRK00. The signal at Test Point 10 should go high between Tracks 2 and 3, as the carriage is being movedtoward TRK 00.

E. WRITE PROTECT


When the drive is selected and the diskette is write protected, the WRITE PROTECT line's true (low).The write electronics are internally disabled when the diskette is write protected (see Option Listingfor exceptions).

When the signal on the WRITE PROTECT line is false (high), the write electronics are enabled and thewrite operation can be performed. It is recommended that the controller not issue a Write commandwhen the Write Protect signal is true (low).

It is recommended that the Write Data line be inactive whenever Write Gate is false (high).

Circuit Description

When a write protected diskette is installed, light from the Write Protect L. E. D. is detected by theWrite Protected sensor transistor. The output of the sensor is high and is conditioned by U32. Theoutput at Pin 14 is low g e nerat ing the s ignal WR PROT-. This signal is used internally with theread/write circuitry. The signal WR PROT- is inverted by U33, and gated with DR SEL+ to generatethe Write Protect signal.

F. READ DATA


The Read Data interface line transmits the read data to the controller when the drive is selected. Itprovides a pulse for each flux transition recorded on the media. The Read Data output line goes true(low) for a duration of 200 nanoseconds for each flux change recorded.

The leading edge of the low going, read data output pulse represents the true positions of the fluxtransitions on the diskette surface.

3-1 2

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Figure 3-10Write Protect Schematic Diagram

Test Points 2 and 3 (see Figure 3-11) are provided to observe the differential output of the first stageof Read signal preamplification. Test Points 4 and 5 are provided to observe the differential output ofthe second stage amplifier and differentiated Read signal. Test Point 9 is the output of thesingle shotused in the Read section, nominally 200 nanoseconds for each flux transition detected. Test Point 1is signal ground.

Circuit Description

The read signal comes from the selected head on the drive. It is gated to the preamplifier U7 by the— Write signal to U25, which forward biases diodes CR14 and CR15. Then, the Read signal passesthrough a linear bandpass filter. The Read signal is then input to U2, the differentiator.

The output of U2 goes through the D. C. blocking capacitors to the crossover detector, U8, whichdigitizes the signal. This converts the signal into standard TTL level Integrated circuits U9, U11, andU10 comprise acorn parator circuit. Any pulses that occur outside of the normal duty cycle of U11 areeliminated. U9 is an edge detector. U11 acts as a one shot, with a t imeout of approximately 860nanoseconds. U10 is the actual comparator.

The Read signal is presented to U9. Then it goes to U11, where the pulses are shaped to 200nanoseconds. This output is gated at U29 with the Unit Select signal to produce a digital output at Pin46 of the interface connector (see Figure 3-12).

Note

U11, the final one shot, is disabled when thedrive is writing data onto the diskette.

G. Two Sided


This output enables the controller to determine if a diskette is installed, which utilizes the Index 2index hole. This may be used to indicate to the host controller that a two-sided diskette is in the drive.

3-1 3

TEST POINT 2

UPPERHEAD

READ AND HEADSWITCHINGCIRCUITS

SIGNALAMPLIFIER

TEST POINT 3

LOWERHEAD

TEST POINT 4

TIME DOMAINDIFFERENTIATOR

CROSSOVERDETECTOR FILTER

TEST POINT S

DATA OUTPUTDIGITIZER

INT WRT BUSY

UNIT SELECT

Figure 3-11Read Circuit Block Diagram

Circuit Description

When a two-sided diskette is installed, the signal IN1FF+ is generated and gated by U4 to enable thelow-going output Two Sided. The IN1FF signal also goes to the ready circuitry at U6-5 to disableReady in the event that the upper head (H ead 1) is selected when a single-sided (Head 0) diskette isinstalled (see Option RM for further discussion).

3-1 4

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Figure 3-12Read Data Schematic Diagram

SECTION IV

TROUBLESHOOTING GUIDE

INTRODUCTION

This section is presented in the form of a table. Each section contains four major parts:

1. The section number.

2. A statement of the presenting condition.

3. A list of the possible causes of the condit ion.

4. I he recommended action to be taken.

4-1

POSSIBLE CAUSE RECOMM EN DED ACTIONS ECTION CONDIT I O N

4.1 NOT READYAND/ORNO INDEX

Diskette not inserted.

Diskette not clamped.

Unit not selected.

Insert diskette.

Turn knob lock leverclockwise so that itis perpendicular tothe diskette insertion slot.

Verify unit select andjumper configuration.

Verify interface drive motor on.

Check Connector P6.

Verify drive belt installed

Replace circuit board.

Replace Drive Motor Assembly.

Drive motor not turning

Index sensor notconnected.Index sensor defective.

Check P1.

Replace index sensor.

4.2 WILL NOT SEEK Inte r f ace not enabled.OR RESTORE

Verify interface direction,step, and select signals.

Check Connectors P4 and P5.


Step motor disconnected.

Defective step logic.

Defective stepper motor . Re p l ace Stepper Motor Assembly.

Wrong option selected. Check options DS and HL for theparticular application.

4-2

SECTION CONDI T I ON POSSIBLE CAUSE RECOMM EN DED ACTION

4.3 WILL NOT WRITE Inte r face not enabled. Verify write enable, select, andwrite data interface lines.

Heads or write protectswitch not connected. Check Connectors P3, P8,

and P9.

Write protect switchmisadjusted.

Defective write logic.

Defective heads.

Check write protectswitch operation.


Replace HeadCarriage Assembly.

Adjust platen load arm.Misadjusted platenload arm.

4.4 WILL NOT READ Inter f ace incorrect.

Alignment off.

Verify select is true andwrite enable is false.

Verify C. E. lobes, indexburst, and Track 00 sensoradjustment.

Replace circuitboard.

Replace Head Carriage Assembly.

Defective readelectronics.

Defective heads.

Platen load armmisadjusted. Adjust platen load arm.

4.5 ACTIVITYL.E.D.INOPERATIVE

Interface not enabled. Verify interfaceselect and jumperconfiguration.

4-3

SECTION CONDI T ION POSSIBLE CAUSE RECOMM EN DED ACTION

4.5 ACTIVITYL. E. D.I NOP E RAT I VE Check P11Activity L.E.D.

not connected.

Replace ActivityL. E. D. Assembly.


Activity L.E.D.defective.

Activity L.E.D.driver defective.

4.6 NO TRACK 00SENSORI N D I CAT I 0 N Defective seek. See Section 4.2

Track 00 sensor notconnected.Defective logic.

Check P2.


Defective Track 00sensor. Replace Track00

Sensor Assembly.

4.7 DRIVE MOTORWILL NOT STARTWHEN DOORLATCHED. Defective microswitch. Replace switch.

Microswitch notconnected.

Misadjusted switchbracket.

Check P14.

Realign.

4-4

SECTION V

REPLACEIVIENT PROCEDURES

5 INTRODUCTION

This section contains the replacement procedures for the TM848 family of disk drives' parts andassemblies:

1. Drive Belt

2. Drive Motor

3. Circuit Board

4. Cone Assembly

5. Diskette Lever

6. Bridge Assembly

7. Front Panel

8. Activity L. E. D.

9. Load Arm Assembly

10. Track OO Sensor Assembly

11. Write Protect Sensor Assembly

12. Door Switch Assembly

13. Index Sensor Assembly

14. Diskette Ejector Assembly

15. Load Resistor Assembly

16. Stepper Band

17. Stepper Motor Assembly

18. Head ( arriage Assembly

DRIVE BELT5.1

5.1.1 R emova l

A. Turn the drive over so that the spindle is facing upward (see Figure 5-1).

5-1

DRIVE BELT

SMALLFLANGEDSPINDLEPULLEY

0

0 0

Oe

LARGESPINDLEPULLEY

Figure 5-1Drive Belt and Spindle

B. Grasp the drive belt, and remove it from the pulleys.

5.1.2 Insta l l a t ion

A. With the shiny side inward, loop the new drive belt onto the small, flanged spindle pulley.

B. While turning the spindle, put the drive belt on the large spindle pulley.

5.1.3 C hecks

A. After turning the drive motor on, check that the drive belt does not slip or fall off the largepulley.

B. Check the spindle speed (see Section II).

5 .2 DRIVE M O T O R

Removal5.2.1

A. Remove the drive belt (see Section 5.1).

B. After turning the drive over, cut the tie wraps that hold the drive motor's wires(see Figure 5-2).

C. Unplug P6 from the circuit board.

D. Remove the three mounting screws that attached the drive motor to the chassis.

E. Lift out the drive motor.


A. Set the drive motor on the chassis, aligning the three mounting holes.

B. Reinstall and tighten the three mounting screws.

5-2

P6

0 p

DRIVEMOTOR Oo

0o

MOUNTING SCREWS(3 PLACES)

TIE WRAPS(12 PLACES)DRIVE MOTOR WIRES

Figure 5-2Drive Motor and Related Parts

C. Carefully rebundle the wires, including the drive motor wire, and cable harness them (seeFigure 5-2).

D. Plug P6 into the circuit board.

E. Turn the drive over, and reinstall the drive belt (see Section 5.1.2).

5.2.3 C hecks

A. Check to ensure that the drive motor works.

B. Check the spindle speed (see Section II).

5 .3 CI RCU I T B OARD

5.3.1 R emo va l

A. Remove all the connectors from the circuit board.

B. Remove the two side mounting screws that connect the two regulator heat sinks to the drive'schassis (see Figure 5-3).

C. Remove the screw and the retaining clip that attach the circuit board to the dirve's chassis.

D. Lift the circuit board away from the drive.

E. Remove the power connector by pushing down on its top. Lift its wires out, using the slotprovided (see Figure 5-3).

Installation5.3.2

A. Install the power connector by re threading the power wires and pushing in the powerconnector from the back of the drive.

5-3

MOUNTING SCREWSCONNECTING HEAT SINKS

POWER CONNECTOR

RETAINING CLIP

SCREW

040Qo 4

Figure 5-3Circuit Board Mounting Screws

B. Remount the circuit board using the two screws to the two heat sinks and the screw and nylonclip that attach the circuit board to the drive's chassis.

C. Plug in all connectors, ensuring that each one is seated correctly in its proper location.

5 .3.3 Che cks

A. Verify the select and options configuration.

B. Applying power, check the operation of the drive.

5 .4 CONE AS S E M BLY

5.4.1 R emova l

A. Remove the screw that attaches the cone bracket to the cone alignment arm (see Figure 5-4).

B. Unlatch the diskette lever.

C. Swing the Cone Assembly up 90 degrees so that it points toward the side of the drive.

D. Carefully remove the E-Ring, flat washer, and washer that holds on the cone shaft.

E. Gently lift out the Cone Assembly.

5.4.2 Instal l a t ion

A. Gently insert the Cone Assembly.

B. Carefully insert the E-Ring, flat washer, and wave washer that holds on the cone shaft (seeFigure 5-5).

C. Swing the Cone Assembly down 90 degrees so that it points toward the bottom of the unit.

5-4

CONE BRACKET

SCREW

CONE ALIGNMENT ARM

E-RING A WASHERWAVE WASHER

DISKETTE LEVER

0 p

Qo

CONE ASSY

Figure 5-4Cone Assembly Key Parts

D. Latch the diskette lever.

E. Insert the screw that attaches the cone bracket to the cone alignment arm(see Figure 5-5).

E-RING

FLAT WASHER

WAVE WASHER

CONE BRACKET

FLAT WASHER (2)

CONE ASSEMBLY

Figure 5-5Cone Assembly Parts

5.4.3 Chec ks

A. Ensure that the Cone Assembly turns freely.

B. If not, reverify that the Cone Assembly has been installed correctly.

C. Insert a diskette.

D. Ensure that the diskette is clamped properly by the cone.

5-5

5.5 DISKET T E LEVER

5 .5.1 Re mov a l

A. Pry off the cover that hides the diskette lever's retaining screw (see Figure 5-6).

SHAFT

MOUNTING SCREW

COVER

DISKETTE LEVER

Figure 5-6Diskette Lever Key Parts

B. Remove the diskette lever's retaining screw.

C. Carefully remove the diskette lever.


A. Put the diskette lever on the shaft.

B. Put a drop of Locktite Number 234 on the threads of the diskette lever's screw.

C. Install and tighten the diskette lever's screw.

D. Put the cover back on the diskette lever.

5 .5.3 C h e c k s

A. Ensure that the diskette lever is perpendicular to the drive when the diskette is clamped. SeeFigure 5-7 for the adjustment.

B. Ensure that the diskette lever is parallel to the drive when the diskette is unclampled. SeeFigure 5-7 for the adjustment.

5.6 BRIDGE A SSEMBLY

5.6.1 R emova l

A. Remove the circuit board (see Section 5.3.1).

B. Remove the diskette lever (see Section 5.5.1).

C. Remove the four bridge mounting screws that attach the Bridge Assembly to the chassis(see) Figur 5-8).

5-6

BEZEL

MOUNTING SCREWS, 2

BEZEL

~ DISKE TTE LEVER0 p

Qo

BEZELMOUNTNG SCREWS. 2Figure 5-7

Diskette Lever Adjustment

BRIDGE MOUNTING SCREWS

2 BOTH SIDES

0o ooBEZEL

SCREWS

2 BOTH SIDES

0 0

Figure 5-8Bridge Assembly Key Parts

D. Carefully pull out the two index L. E. D.'s in the Bridge Assembly.

E. Carefully lift out the Bridge Assembly toward the back of the drive. The shaft must clear thebezel.

Installation5.6.2

A. Insert the shaft into the bezel and lay the Bridge Assembly in place.

B. Install and tighten the four bridge mounting screws that attach the Bridge Assembly to thechassis.

C. Install the two index L . E. D.'s into the Bridge Assembly.

D. Install the diskette lever (see Section 5.5.2).

E. Install the circuit board (see Section 5.3.2).

5.6.3 Checks

A. Ensure that the diskette lever clamps the cone and loads the head (see Figure 5-9).

5-7

MOUNTING SCREWS (2 EA SIDE)

BRIDGE ASSY

Q4

INDEX L.E.D.'s (2)

4 O4 p p

~D I S KETTE LEVER4 p

Q4

0o

SHAFT

Figure 5-9MOUNTING SCREWS(2 EA SIDE)Bridge Assembly Additional Key Parts

BEZEL5.7

5.7.1 R emova l

A. Remove the diskette lever (see Section 5.5).

B. Remove the four bezel mounting screws, two on each side, that attach the bezel to thechassis (see Figure 5-10).

BEZELMOUNTING SCREWS 2

BEZEL

0+ .. 0+P 2 P3 P I

~ DISK E TTE LEVER

Oo

BEZELMOUNTING SCREWS. 2

Figure 5-10Bezel and Related Parts

C. Lift off the bezel, being careful that the Activity L. E. D. comes out of its mounting with nobinding.

5-8


A. Put the bezel on the drive, ensuring that the Activity L. E. D. goes into its holder.

B. Install the four bezel mounting screws that attach the bezel to the chassis.

5.7.3 C hec ks

A. Ensure that the Activity L. E. D. goes on when required.

B. Ensure that the diskette lever clamps the cone and loads the head.

ACTIVITY L. E. D.5.8

Removal5.8.1

A. Remove the bezel (see Section 5.7.1).

B. Remove the brackets that hold the bundle of wires going to P11 from the chassis (see Figure5-1 1).

TIE BRACKETS2 FAR SIDE

ACTIVITY LIGHT WIRES

Co

o 0

Qo TIE

BRACKET

1 NEAR SIDEACTIVITY L.E D

(INSIDE)

Figure 5-11Activity L. E. D. Key Parts

C. Remove the Activity L. E. D. and its wires after unplugging P11.

5.8.2 Installation

A. Install the Activity L. E. D. into the bezel.

B. Install the bezel.

C. Attach the Activity L. E. D. wires to the chassis with brackets (see Figure 5-11).


5.8.3 C hecks

A. Ensure that the Activity L. E. D. does not interfere with the drive mechanisms.

B. Ensure that the Activity L. E. D. goes on when required.

5-9

5.9 LOAD A R M ASSEMBLY

5.9.1 R emova l


B. Remove the mounting screw and washer that are used to attach the Load Arm Assembly tothe chassis (see Figure 5-12).

0+

llfllflflIIIJIIII

0 0

po

LOAD ARM REAR MOUNTING SCREW, WASHER, AND SPRING

Figure 5-12Load Arm Assembly Key Parts

C. Carefully slide out the Load Arm Assemblytoward the rear of the chassis.


A. Slide the Load Arm Assembly into position from the rear of the chassis, ensuring that the loadspring is sitting under the front of the mounting screw.

B. Install and tighten the mounting screw that attaches the Load Arm Assembly to the chassis,ensuring that the washer is under the screw and that the head lift arm is over the Load ArmAssembly.

C. Install the circuit board (see Section 5.3.2).

5 .9.3 Checks

A. Insert a diskette in the drive.

B. Ensure that the head is loaded when the d iskette fever is act ivated and that adequateclearance is attained for diskette insertion and ejection (see Section II).

5.10 TRAC K 0 0 SENSOR ASSEMBLY

5.10.1 Removal

A. Remove P2 from the circuit board.

B. Cut the tie wraps that hold the cable harness, and remove the P2 wires (see Figure 5-13).

5-10

TRACK 00SENSORASSEMBLY

MOUNTINGSCREWS2

0 . 0 +P S P IP2

BRACKET

Qo

0o

TIE WRAPS

Figure 5-13Track 00 Sensor Assembly Key Parts

C. Remove the P2 wires from the bracket attached to the chassis.

D. Remove the two mounting screws that hold down the Track 00 Sensor Assembly.

E. Lift off the Track 00 Sensor Assembly.

5.10.2 Inst a l lat ion

A. Using the two original mounting screws, install the Track 00 Sensor Assembly.

B. Loop the P2 wires from the Track 00 Sensor Assembly through the bracket attached to thechassis.

C. Using tie wraps, cable harness the P2 wires and the other wires together.

l3. Plug P2 into the circuit board.

5 .10.3 Ch ec k s

A. Adjust the Track 00 sensor (see Section II).

5.11 W R I TE PROTECT SENSOR ASSEMBLY

5 .11.1 Re mo v a l


B. Remove the two mounting screws that attach the Write Protect Sensor Assembly to thechassis (see Figure 5-14).

C. Cut the tie wraps that hold the wires to the cable harness, and lift out the Write Protect SensorAssembly.

5-1 1

MOUNTING SCREWS (2) '

$ . . $P2 P3 P I

Oo0o

WRITE PROTECT SENSOR ASSY.

Figure 5-14Write Protect Sensor Assembly Key Parts

5.11.2 Ins t a l lat ion

A. Using the two original mounting screws, attach the Write Protect Sensor Assembly to thechassis.

B. Plug P3 into the circuit board.

C. Tie wrap the Write Protect wires to the cable harness.

5.11.3 C heck s

A. Verify operation of the Write Protect Sensor Assembly.

DOOR SWITCH ASSEMBLY5.1 2

5 .12.1 Re m o v a l


B. Remove the mounting screw from the door switch bracket (see Figure 5-15).

C. Cut the tie wraps leading to P14.

D. Lift out the Door Switch Assembly.


A. Mount the Door Switch Assembly to the bridge, using the original mounting screw.

B. Plug P14 into the circuit board.

5 .12.3 Chec k s

A. Ensure that the door switch operates properly.

5-1 2

5.13 INDEX S E NSOR ASSEMBLY

MOUNTING SCREW

P14

p 8 • ~ 0+P3 P IPZ

QO

0oDOOR SWITCH ASSEMBLY

Figure 5-15Door Switch Assembly Key Parts

5 .13.1 Re mo v a l


B. Gently remove the two index L. E. D. 's from the Bridge Assembly (see Figure 5-16).

P1

UPPER INDEX SENSORS

0+ ., SP3 P IP2

QO

C0

TIE WRAPS

Figure 5-16Index Sensor Assembly Key Parts, Top View

C. Turn the drive over and remove the mounting screw from the Index Sensor Assembly (seeFigure 5-17).

D. Remove the two brackets that attach the Index Sensor Assembly's wires to the chassis(seeFigure 5-16).

5-1 3

E. Cut the tie wraps along the cable harness (see Figure 5-16).

F. Lift out the Index Sensor Assembly (P1).

TIE BRACKETS, 2 FAR SIDE TIE BRACKET, I NEAR SIDE

0

0 0 0

0 0

LOWER INDEX SENSOR ASSEMBLY

(60IMOUNTING SCREW

QAtoll i<A4 MNI SIIIII

@ 0

Figure 5-17Index Sensor Assembly Key Parts, Bottom View


A. Put the Index Sensor Assembly into the drive.

B. Loop the wires to the cable harness and chassis.

C. Insert the two L. E. D. index sensors into their sockets.

D. Using the original mounting screw, attach the index L. E. D. to the drive's chassis.

E. Cable harness the bundle of wires, including the Index Sensor Assembly's wires.

F. Reinstall the circuit board (see Section 5.3.2).

5 .13.3 Chec k s

A. Check the index-to-data adjustment (see Section II).

DISKETTE EJECTOR ASSEMBLY5.1 4

5 .14.1 Re m o v a l


B. Remove the door lock lever (see Figure 5-6).

C. Locate and remove the four screws, two on each side, that hold the Bridge Assembly (seeFigure 5-7).

5-1 4

TRIGGER HOLD DOWN SCREWEJECTOR

IIIIIIIIIIIIIIIIIPIVOT BAR

EJECTOR SPRING

TRIGGER ASSEMBLY

Figure 5-18Diskette Ejector Assembly Key Parts

D. Lift up the Bridge Assembly approximately two inches, taking care not to pull the L. E. D.'sfrom their sockets.

E. Release the spring attached to the rear of the ejector.

F. Remove the ejector.


A. Insert the ejector.

B. Engage the spring attached to the rear of the ejector.

C. Insert the Bridge Assembly approximately two inches, taking care to put the L. E. D.'s in theirrespective sockets.

D. Reinstall the original four screws that hold the Bridge Assembly.

E. Push on the lever. Reinstall the retaining screw. Insert the small plug in the door lever.

F. Reinstall the circuit board (see Section 5.3.1).

5 .14.3 Ch ec k s

A. Insert a work diskette into the drive.

B. Ensure that the diskette stays in prior to being closed.

C. Close and open the diskette lever.

D. The diskette should eject.

E. If not, see Section 5.4.

5.15 LO A D RESISTOR ASSEMBLY

5-1 5

5.1 5.1 Re m oval


B. Remove the circuit board (see Section 5.3.1).

C. Remove the two mounting screws that attach the Load Resistor Assembly to the chassis.

D. Unsolder the wires to the load resistors (see Figure 5-19).

E. Mark or identify these wires so that they can be put back in the same location.

MOUNTING SCREWS, 2LOAD RESISTOR ASSEMBLY.

SOLDER JOINT, 4 PLACES

IIlllllllllflllll

0 0

o o o

0 p

0o

JlFig ure 5-1 9

Load Resistor Assembly and Key Parts


A. Solder the wires back in the same place at which they were originally.

B. Mount the Load Resistor Assembly onto the chassis using the two original mounting screws.

C. Install the circuit board (see Section 5.3.2).


5 .15.3 C hec k s

A. Enable the drive through the interface logic.

B. Step the drive to Track 00.

C. Step the drive to Track 76.

D. Do the C. E. alignment verification procedure (see Section II).

5-16

5.16 STEPP E R BAND

5 .16.1 Re mo v a l

It is suggested that the drive be returned to an authorized Tandon repair center when removing thestepper band.


B. Lift off the stepper band from the spring tensioner (see Figure 5-20).

SCREW, ATTACHES BAND TO CARRIAGE ASSEMBLY

SPRING TENSIONER ~C ARRIAGE ASSEMBLY0 O

Qo

STEPPER BANDSTEPPER PULLEY SCREW, ATTACHES BAND TO STEPPER PULLEY

SPRING TENSIONER

Figure 5-20Stepper Band Key Parts

C. Remove the screw that attaches the front of the stepper band to the Head Carriage Assembly.

D. Remove the mounting screw that attaches the stepper band to the stepper pulley.

E. Lift out the stepper band.


A. Screw the front of the stepper band'into the Head Carriage Assembly (see Figure 5-21).

B. Loop the stepper band around the stepper pulley.

C. Attach the rear of the band to the spring tensioner.

D. Attach the stepper band to the stepper pulley loosely with the mounting screw.

E. Move the Head Carriage Assembly back and fourth at least five times.

F. Visually inspect the stepper band to ensure that it is centered on the stepper pulley.

G. Tighten the mounting screw that attaches the stepper pulley to the stepper band.

H. Install the circuit board (see Section 5.3.2).

5.1 6.3 C h ecks

A. Check the C. E. alignment (see Section II).

5-1 7

MOUNTING SCREWS, 3 PLACESSTEPPER MOTOR ASSEMBLY

0

4

o QQo

0 O

Qo0

0

(> 0

Figure 5-21Stepper Band Additional Key Parts

5.17 STEPP E R MOTOR ASSEMBLY

5 .17.1 Re m o v a l

It is suggested that the drive be returned to an authorized Tandon repair center when removing theStepper Motor Assembly.


B. Remove the stepper band (see Section 5.16.1).

C. Remove the three mounting screws that attach the Stepper Motor Assembly to the chassis(see Figure 5-2 2).

D. Remove plug connectors P4 and P5 from the circuit board.

E. Cut the tie wraps that connect the stepper motor wires to the load resistors.

F. Lift out the Stepper Motor Assembly.

Note

Be careful not to damage the stepper band.


A. Place the Stepper Motor Assembly into the drive's chassis.

B. Using the original three mounting screws, attach the Stepper Motor Assembly to the chassis.

5-1 8

STEPPER MOTOR ASSEMBLY MOUNTING SCREWS, 3 PLACES

p+

o QQO

pb

• •

~ 0 0

' .ig

~o0 0

o0

Qo0

Figure 5-22Stepper Motor Assembly Key Parts

C. Replace the stepper band (see Section 5.16.2).

D. Replace the circuit board (see Section 5.3.2).

5.17.3 C heck s

A. Align the C. E. lobes on the drive (see Section II).

5.18 HEAD C A R RIAGE ASSEMBLY

5 .18.1 Re mo v a l

It is suggested that the drive be returned to an authorized Tandon repair center when removing theHead Carriage Assembly.

A. Remove the Stepper Motor Assembly (see Section 5.17.1).

B. Remove plug connectors P8 and P9 from the circuit board.

C. Cut the tie wraps that hold the head cables to the chassis.

D. Remove the clip that holds the head cables to the head cable flexure bracket.

E. Remove the four mounting screws that attach the carriage shaft to the chassis (see Figure 523).

5-19

0

00

0 OO

Qo0o

MOUNTING SCREWS 4 PLACES

Figure 5-23Head Carriage Removal

F. Lift out the Head Carriage Assembly.


A. Install the carriage shaft in the carriage.

B. Using the four original mounting screws, attach the carriage shaft to the chassis.

C. Install the Stepper Motor Assembly (see Section 5.17.2).

Note

Take care not to damage the Arm Spring Assembly.

D. Plug connectors P8 and P9 into the circuit board.

E. Cable harness the Head Carriage Assembly's wires to the main wire bundle.

5 .18.3 Ch ec k s

A. Check the azimuth (see Section II).

B. Check the Cats Eye alignment (see Section II).

C. Check the index alignment (see Section II).

5-20

APPENDIX I

PRINTED CIRCUIT BOARDSCHEMATICS AND ASSEMBLY DRAWINGS

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APPENDIX II

RECOM M E N D E D SPARE PARTS LIST

PARTS AND SUBASSEMBLIES

Part NumberPart

Drive BeltDrive MotorCircuit BoardCone AssemblyDiskette LeverBridge AssemblyBezelActivity L. E. D. (Front Panel)Load Arm AssemblyTrack 00 Sensor AssemblyWrite Protect Sensor AssemblyDoor Open Switch AssemblyIndex Sensor AssemblyDiskette Ejector AssemblyHead Carriage Assembly:

Single-Sided RecordingDouble-Sided Recording

21 0062-00021 0061-00021 0094-00021 0085-00021 0084-00021 0086-00021 001 1-00021 0081-00021 0089-000210080-00021 0079-00021 0083-00021 0075-00021 01 24-000

21 0065-00121 0065-00221 0090-00021 01 1 2-00021 0076-0002 1 0082-00021 0036-00021 01 22-000

Stepper Motor (Mounting) AssemblyStepper BandLoad (Power) ResistorsDiskette Lever LockEjector SpringLoad Arm Spring

Note

All components are standard commercial parts purchased to originalequipment manufacturer's specifications.

OEM OPERATING AND SERVICE MANUAL, TM848-1 AND TM848-2 THINLINE ™ DISK DRIVES, 48TPI, TANDON P/N 179031-001

ALIGNMENT DISKETTERecommended: Dysan 8006 0, Model Number 360/2A

Pi N 1 79031-001 (1 082)

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