Tandon TM848-2 Operating And Service Manual

OEM OPERATING

AND

SERVICE

MANUAL

TM848-1

AND

TM848-2

DISK

DRIVES

48

TRACKS

PER

INCH

'anCion

CORPORATION

20320

PRAIRIE STREET

CHATSWORTH, CA

91311

TELEPHONE

NO.: (213)

993-6644

TWX NO.:

910

494

1721

TEL.EX NO.:

194794

COPYRIGHT

1982

TANDON CORPORATION

The

information

containedinthis

documentisthe

property

of

Tandon Corporation. It may

notbeduplicated

in fullorpart

by

any

person

without

prior

written

approval. The material in

this

documentisprovided

for

informational

purposes,

andissubject

to

changebyTandon Corporation.

Sectoon

Number

SECTION

I

TABLE

OF

CONTENTS

TitleofSection

INTRODUCTION

TOTHETM848

FAMILYOF

DISKDRIVES

Page

Number

1.

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

1.10

1.10.1

1.10.2

1.10.3

1.11

1.12

1.13

1.14

1.15

1.15.1

1.15.2

1.15.3

1.15.4

1.15.5

1.16

1.16.1

1.16.2

1.17

1.17.1

1.17.2

1.17.3

1.18

1.19

1.19.1

1.19.2

1.19.3

1.19.4

1.19.5

1.19.6

1.19.7

1.19.8

1.19.9

1.19.10

1.19.11

1.19.12

1.19.13

1.19.14

1.19.15

1.19.16

1.19.17

Introduction

1-1

PurposeOfThe

Drive

1-1

Physical

DescriptionofThe

Drive

1-1

Functional

DescriptionofThe

Drive

1-1

Diskettes

1-2

Mechanical

and

Electrical

Sepcifications

1-2

Power

Requirements

1-2

Interface

Circuit

Specifications

1-2

Incoming

Inspection

Checks

and

Procedures

1-2

Interface

Connections

1-5

Mounting

The

Drive.." " ,

1-5

Hardware

"1-6

Dust

Cover.

1-6

Cooling

System

Requirements

1-6

Diskette

Care,

Handling

and

Storage

1-6

Write

Protect.

1-7

OperationofThe

Drive

1-7

OrganizationofThe

Drive

1-7

ComponentsofThe

Drive

'"

1-7

Index

Pulse

" , "

1-8

Drive

Status

Logic

"

1-8

Spindle

Drive

System

1-9

Positioner

Control

"

1-9

Data

Electronics

1-9

Interface

Electronics

"

'"

1-12

Interface

Connector

Assignments,

P13

1-12

Power

Connector

Assignments

1-12

Terminated

Lines

1-14

Input

Line

Terminations

From

Removable

Resistor

Pack

1-14

Drive

Select.

1-14

Program

Shunt

1-14

DS

and

HL

Power

Save

Options

1-17

User-Selectable

Options

1-17

Drive

Select

DS1--DS4

,

1-18

Side

Select

Options

Using

Drive

Select

18--48

1-18

In

Use

From

Drive

Select

1-18

In

Use

From

Head

Load

"

'"

1-18

Ready

Alternate

Output

Pad

1-18

Radial

Ready..'"

'"

1-19

Ready

Modified

1-19

Radial

Index

"

1-19

I

ndex

Alternate

Output

Pad

1-20

In

Use

Altenate

Output

Pad

1-20

Diskette

Lever

Lock

Latch

Option

1-20

Disk

Change

1-20

Two-Sided

Diskette

Installed

1-20

Stepper

Power

From

Drive

Select

1-21

Stepper

Power

From

Head

Load

Line

, 1-21

Head

Load

Alternate

Output

Pad

Option

1-21

Radial

Head

Load

Signal

Option

1-21

Section

Number

TitleofSection

Page

Number

1.19.18

1.19.19

1.19.20

1.19.21

1.19.22

Inhibit

Write When

Write

Protected

, 1-21

Allow

Write

When

Write

Protected

1-21

Head

Side

Select

Options

S1-S3

,

1-22

Spindle

Motor

Control

Options

M1 -

M4

1-22

Motor

Control

Select

Options

MC1 -

MC4

1-22

SECTION

II

MAINTENANCE

CHECKS

AND

ADJUSTMENTS

2.

Introduction

2-1

2.1

Spindle

Drive

Motor

Checks

and

Adjustments

2-1

2.1.1 Long-Term Drive

Motor

Speed

Checks

and

Adjustments

,

2-1

2.2

Cats

Eye

Alignment

Check

and

Adjustment

2-2

2.2.1

Cats

Eye

Alignment

Check

2-4

2.3

Head

Carriage

Adjustment

2-5

2.4

Index

Sensor

Checks

and

Adjustments

2-6

2.4.1 Index-To-Data Burst

Checks

2-6

2.4.2

Index

Sensor

Adjustment

, 2-7

2.4.3

Index

Pulse Width

Check

2-8

2.5 Track

00

Sensor

Check

and

Adjustment

2-8

2.6

Amplitude

Check

2-9

2.7

Azimuth

Check

2-10

2.8

Load

Arm

Adjustment

2-10

SECTION

III

PRINTED

CIRCUIT

BOARD

OPERATION

3.

3.1

3.2

3.3

3.4

Introduction

3-1

Physical

DescriptionofThe

Circuit

Board

3-1

Interface

Electronics

Specifications

3-1

Input

Control

Lines

3-2

Output

Control

Lines

3-7

SECTION

IV

TROUBLESHOOTING

GUIDE

4.

4.1

4.3

4.4

4.5

4.6

4.7

Introduction

" "

.,

"..4-1

Not

Ready

and/or

No

Index

,..4-2

Will

Not

SeekorRestore

4-2

Will

Not

Write

4-3

Will

Not

Read

4-3

Activity

L.E.D.

Inoperative

4-3

No

Track00Sensor

Indication

4-4

Drive

Motor

Will

Not

Start

When

Door

Latched

4-4

SECTION V REPLACEMENT PROCEDURES

5.

Introduction

5-1

5.1

Drive

Belt

5-1

5.2 Drive

Motor

5-2

5.3

Circuit

Board 5-3

5.4

Cone

Assembly

5-4

5.5

Diskette

Lever

, " 5-6

5.6

Bridge

Assembly

5-6

5.7 Bezel 5-8

ii

Section

Number

TitleofSection

Page

Number

5,8

5,9 5,10 5,'11 5,12 5,13

5,'14

5,'15

5,'16 5,'17

5.'18

ActivityL,E,

D",.

, " , " , . ,","""

, . ,.,, . "

., .,",..

, . , ,, . ,. , "

",.,, 5-9

Load

Arm

Assembly,.,..

, , , ,. , ,, . , ,, , ,, , .,

...

, , , ,. , ., , . , , , , ,. , ,. , . ,.., . , .

5-10

Track00Sensor

Assembly,

,, , ,, , ,. , , ,, . ,, , . ,, . ,. , . , ,..,.., , . , ., , ., , , .

5-10

Write

Protect

Sensor

Assembly,

,, , ,. , ,, , , ,, , ., , . ,. ,..,.., 5-11

Door

Switch

Assembly.., , , ,.., , . , ,, , , , ,

5-12

Index

Sensor

Assembly.,.,.., , , .,.,, "..,

5-12

Diskette

Ejector

Assembly

, , , ,,.., , , , , ,

5-14

Load

Resistor

Assembly,

, , , ,. , ,, , .,,.., , , . ,

5-15

Stepper

Band,

, , , , , , , , , ,..,, ,

5-16

Stepper

Motor

Assembly

,.,,.., , ,

.,

, , ,

5-18

Head

Carriage

Assembly""

..

"",

..

" , , ,

5-19

APPENDIX I PRINTED CIRCUIT BOARD SCHEMATICS AND

ASSEMBLY

DRAWiNGS"",

".,."",

, " , ,

1-1

APPENDIXIIRECOMMENDED

SPARE PARTS LIST , ".., ,

11-1

iii

LIST

OF

ILLUSTRATIONS

FIGURES

Figure Number

TitleofFigure

Page

Number

1-1

TM848

Disk

Drive

Mounting

Configuration

" 1-6

1-2

TM848

Disk

Drive

Functional

Block

Diagram " 1-9

1-3 FM

Recording

Magnetization

Profiles

1-10

1-4

Write

Operation

Timing Diagram 1-11

1-5 Read Timing Diagram

1-12

1-6

Circuit

Board

Assembly

" " '

1-15

1-7

General

Control

and

Data Timing

Requirements

,..,

1-16

1-8 Radial Ready

Installation.." " "

1-19

1-9 Radial I

ndex

Installation

1-20

1-10

Radial

Head

Load

Signal. 1-21

2-1

Circuit

Board

Assembly

2-2

Hub

Center

Line

and

Track

Locations

2-3

Cats

Eye Pattern 2-4

2-4

Head

Module

Retaining

and

Cam

Screws

2-5

Index-to-Data

Burst.." , 2-7

2-6

Index

Sensor's

Retaining

Screw

and

Adjustment.

2-7

Negative

Going

Pulse

Width

2-8

Track

00

Sensor

2-9

Optimum

Head

Azimuth

Alignment.

2-11

2-10

Head

Azimuth

Alignment

Acceptable

Lower

Limits

2-11

Head

Azimuth

Alignment

Acceptable

Upper

Limits

, 2-12

2-12

Load

Arm Adjustment,

Front

View 2-12

3-1

Printed

Circuit

Board

3-1

3-2

Interface

Configuration

3-1

3-3

S~lect

Lines

Schematic

Diagram 3-2

3-4

Write

Data

Circuit

Block

Diagram 3-6 3-5 Trim Erase Diagram 3-8 3-6 Side

Select

Schematic

Diagram 3-9

3-7

Index

Schematic

Diagram , 3-11

3-8 Waveform

at

Test Point7,Soft

Sectored

3-11

3-9

Track

00

Schematic

Diagram

3-12

3-10

Write

Protect

Schematic

Diagram " "

3-13

3-11 Read

Circuit

Block

Diagram " "

3-14

3-12

Read

Data

Schematic

Diagram

3-15

5-1

Drive

Belt

and

Spindle

5-2

5-2 Drive

Motor

and

Related Parts 5-3

5-3

Circuit

Board

Mounting

Screws

" 5-4

5-4

Cone

Assembly

Key Parts 5-5

5-5

Cone

Assembly

Parts 5-5

5-6

Diskette

Lever

Key

Parts 5-6

5-7

Diskette

Lever

Adjustment

5-7

5-8

Bridge

Assembly

Key

Parts " 5-7

5-9

Bridge

Assembly

Additional

Key

Parts " 5-8

iv

Figure Number

TitleofFigure

FIGURES

Page

Number

5-10

Bezel

and

Related Parts 5-8

5-1

"I

Activity

L.

E.

D.

Key

Parts 5-9

5-12

Load

Arm

Assembly

Key

Parts

5-10

5-13

Track00Sensor

Assembly

Key

Parts 5-11

5-14

Write

Protect

Sensor

Assembly

Key

Parts

5-12

5-15

Door

Switch

Assembly

Key

Parts

5-13

5-16

Index

Sensor

Assembly

Key

Parts, Top View

5-13

5-17

Index

Sensor

Assembly

Key

Parts,

Bottom

View

5-14 5 5-18

Diskette

Ejector

Assembly

Key

Parts ,

5-15 5-19

Load

Resistor

Assembly

and

Key

Parts

5-16 5-20

Stepper

Band

Key

Parts

5-17 5-21

Stepper

Band

Additional

Key

Parts

5-18 5-22

Stepper

Motor

Assembly

Key

Parts

5-19 5-23

Head

Carriage

Assembly

Key

Parts

5-20

TABLES

Table

Number

TitleofTable

Page

Number

1-1 1-2 1-3 1-4 1-5

3-1 3-2

Mechanical

and

Electrical

Specifications

1-3

Power

Requirements

1-4

Interface

Connector

Assingments

1-13

Power

Connector

Assignments

1-14

Options

1-17

Drive

Interface

Lines

and

Connectors

'"

,

3-3

Stepper

Logic

Truth Table

3-5

v

SECTION

I

INTRODUCTION

TO

THE

TM848

FAMILY

OF

DISK

DRIVES

1.

INTRODUCTION

This

section

containsadescriptionofthe

physical and

functional

specifications

forthe

TM848-1

and-

2

disk

drives,48tracks

per

inch (TPI),

manufacturedbyTandon

Corporation.

1.1

PURPOSE

OF

THE DRIVE

The drive is an

eight-inch

disk

memory

designed

for

random

access

data

entry, storage,and retrieval

applications. These

applications

typically

are

intelligent

terminal

controllers,

microcomputers,

word

processing

systems,

data

communications

systems,

error

logging,

microprogram

loading, point-of-

sale terminals,

and

Winchester

back

ups.

The drive is

capableofrecording

and reading

digital

data, using FM,

and

MFM.

1.2 PHYSICAL DESCRIPTION

OF

THE DRIVE

The drive

canbemountedinany

verticalorhorizontal

plane. However,

when

mounted

horizontally,

the

printed

circuit

board

must

be up.

The

spindleisbelt

drivenbya

brushless

D.C.

motor

withanintegral

tachometer.

The

servo

control

circuit,

suitably

sized pulleys, and

the

tachometer

control

the

speedofthe

spindle. The Read/Write,

double-sided

head

assemblyispositionedbymeansofa

stepper

motor,

split

band,

and

a pulley.

The

Read/Write/Erase

head

assembly

is a

glass-bonded

manganese/zinc

ceramic

structure.Ithas a

life in

excessof20,000

hours.

For

diskette

loading,

operator

access

is provide via a

slot

locatedonthe

frontofthe

drive.

The

electronic

componentsofthe

drive are

mounted

on a

circuit

board

assembly

locatedinthe

chassis.

Power

and

interface

signalsarerouted

through

connectors

that

plug

into

the

back

ofthe

drive.

1.3 FUNCTIONAL DESCRIPTION

OF

THE DRIVE

The drive is

fully

self-contained.

It requires

no

operator

intervention

during

normal operation. The

drive

consistsofa

spindle

drive

system, a head

positioning

system,

andaread/write/erase

system.

The TM848-1 is a

single-sided

drive. The

TM848-2

is a

double-sided

drive. The

only

difference

between

the

two

drives is

the

numberofheads. The

circuit

boardisidenticalinboth

models.

When

the

diskette

lever

is opened,

accessisprovided

for

the

insertionofa

diskette.

The

diskette

is

accurately

positionedbyplastic

guides.The

disk

positionisensuredbythe

backstop

and

disk

ejector.

Closing

the

diskette

lever

activates

the

cone/clamp

system,

resultingincenteringofthe

diskette

and

clampingofthe

diskettetothe

drive hub. The

drive

hub

is drivenata

constant

speedof360

RPMbya

servo-controlled

brushlessD.C.

motor. The head is

loaded

into

contact

with

the

recording

medium

whenever

the

diskette

lever

is latched.

1-1

The head is

positioned

over

the

desired

trackbymeansofa

stepper

motor/band

assembly

and

its

associated

electronics. This

positioner

employs

a 3.6

degree

rotationtocauseaone-track

linear

movement.

Whenawrite-protected

disketteisinserted

into

the

drive,

the

Write

Protect

sensor

disables

the

write

electronicsofthe

drive,

andaWrite

Protect

status

output

signal is availabletothe

interface.

When

performingawrite

operation, a

0.013-inch

wide

(nominal)

data

track

is recorded. This

track

is

then

tunnel

erasedto0.012

inch

(nominal).

Data

recovery

electronics

include

a low-level head amplifier, a

differentiator,azero

crossing

detector,

and

digitizing

circuits.

No

data-clock

separation

is provided.

In addition,

the

drive is

supplied

with

the

following

sensor

systems:

1.Atrack00sensor

that

senses

when

the

Head

Carriage

AssemblyispositionedatTrack

00.

2.

The

two

index

sensors, eachofwhich

consistsofa L.E.D.

light

source

andaphototransistor,

are

positionedsothat

a signal is

generated

whenaindex

holeisdetected.

The drive can

determine

whether

asingle-ordouble-sided

diskette

is installed. This

output

signalis

present

at

the

interface.

3.

The

Write

Protect

sensor

disables

the

drive's

write

electronics

wheneverawrite-enable

tab

is

removed from

the

diskette

(see

Section

1.12).

1.4 DISKETTES

The drive

usesastandard

eight-inch

diskette.

Diskette$

are available

withasingle

index

hole

orwith

index

and

sector

holes.

They

also are available

double-orsingle-sided.

Single

index

hole

diskettes

are used

when

sector

informationispre-recordedonthe

diskette

(soft

sectoring).

Multiple

index

hole

diskettes

provide

sector

pulsesbymeansofthe

index

sensor

and

electronics

(hard sectoring).

1.5

MECHANICAL

AND ELECTRICAL SPECIFICATIONS

The

mechanical

and

electrical

specificationsofthe

drive are listed in Table 1-1.

1.6 POWER REQUIREMENTS

The

power

requirementsofthe

drive

are

listed

in Table 1-2.

1.7 INTERFACE CIRCUIT SPECIFICATIONS

The

interface

circuits

are

designedsothatadisconnected

wire

results

in a false signal.

Levels:

True

=

+0.4V,maximum

False

=

+2.4V,minimum

1.8

INCOMING

INSPECTION

CHECKS

AND PROCEDURES

There are

two

kindsofrecommended

incoming

inspection

checks

and

procedures:

static

and

dynamic

ones.

The

static

incoming

inspection

checks

include

the

minimum

steps

that

should

be

takentoensure

that

the

driveisoperational

when

received.

1-2

TABLE

1-1

MECHANICAL

AND

ELECTRICAL

SPECIFICATIONS

MECHANICAL Height:

2.30

inches

Width: 8

inches

ELECTRICAL

+ 5 V

D.C.Power:

+24VD.C.Power:

Selected

Motor

On:

Deselected:

Spindle

Motor:

Start

Current

Surge:

ENVIRONMENTAL Operating

Temperature:

Storage

Temperature:

Wet

Bulb

Temperature:

Noncondensing

Operating

Humidity:

RELIABILITY

MTBF: MTTR:

Error

Rates:

Soft

Read:

Hard

Read:

Seek

Errors: PERFORMANCE Head

Wear

Guarantee:

NumberofTracks:

Track-To-

Track

Access

Time:

Head

Settling

Time:

Average

Access

Time,

including

head

settling

time:

Motor

Start

Time:

Disk

Rotational

Speed:

I

nstantaneous

Speed

Variation:

Flux

Changes

Per

Inch,

Inside

Track:

Transfer

Rates:

Unformatted

Recording

Capacity:

IBM

Format

Recording

Capacity:

Recording

Method:

1-3

Length:

13.125

inches

behind

front

panel

Weight:

5.5

pounds

+5

volts

± 5 percent,

0.75

amp

typical

+24

volts±10

percent

0.75

amp

typical

0.20

amp

typical

OAO

amp

typical

2.5 amps,

400

msec

on,

24

volts

total

4.4°Cto46°C

(40°Fto115°F)

-40°C

to

71°C

(-40°F

to

160°F)

26°C (78°F)

maximum

20-to-80

percent

10,000

power-on

hours

30

minutes

1 in

109bits

1 in

1012bits

1 in

106seeks

15,000

media

hours

77

for

TM848-1;

154

for

TM848-2,

77

per

surface

3

milliseconds

15

milliseconds

91

milliseconds

700

milliseconds

360

RPM

± 1.0

percent

6536

FCI,

Side0,both

models;

6818

FCI,

Side1,TM848-2

only

250K

BPS

single

density,

500K

BPS

double

density

0.8 M

Bytes

per

disk,

single

density,

double-sided

drive

1.6

MBytes

per

disk,

double

density,

double-sided

drive

0.6

MBytes,

single

density,

double-sided

drive

1.2 MBytes,

double

density,

double-sided

drive

FM

single

density, MFM

double

density

TABLE 1-2

POWER REQUIREMENTS

1.

+5

Volts:

0.70

Amps

typical

2.

+24

Volts:

After

motor

start

interval

Spindle

Motor

0.35

Amps

typical

Stepper

Motor

0.40

Amps

typical

Electronics

0.17 Amps

typical

Total

0.92

Amps

typical

3.

+24

Volts:

During

motor

start

interval

a.

Configured

for

stepper

motor

enabled

during

motor

start.

2.5 Amps

typical

surge.

2.5

(j)

2.0

a..

~

1.5

z

w

a: a:

1.0

::::>

()

0.5

"

\..

100

200

300

400

TIME (MILLISECONDS)

b.

Configured

for

stepper

motor

disabled

until

motor

comes

up

to

speed.

2.1

Amps

typical

surge.

500

600

500

400

300

200

100

I STEPPER MOTOR

ENABLED

"

V

~

I

•

2.5

en

2.0

a..

~

1.5

z

w

a: a:

1.0

::::>

()

0.5

TIME (MILLISECONDS)

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

arenoscratches

on

the

bezel.

D.

Ensure

that

all

internal

connectors

are

seated

properly.

E.

Turn

the

diskette

lever

counterclockwise,

and

remove

the

shipping

diskette.

F.

Insertablank

diskette,

close,

and

then

open

the

diskette

lever. The

diskette

should

eject.

G.

Insertablank

diskette,

and

manually

turn

the

spindle

pulley.Itshould

rotate

freely.

The

dynamic

incoming

inspection

procedures

include:

A.

Connect

the

drivetoan

exerciserorcomputer

tester

capableofseeking,writing,

and

reading.

B.

Power

up

the

test

equipment,

and

apply

powertothe

drive.

C.

Select

the

drive,

and

ensure

that

the

Activity

L.E.D.

located

on

the

bezel

illuminates.

D.Insertawork

diskette

and

write/verify

from Track00to

Track

76.

Ensure

that

there

are

no

errors.

E.

I

nsertadiskette

written

previouslyonanother

drive. Read

this

diskette,

and

ensure

that

there

arenodata

errors. If

excessive

errors

occur,

check

the

disketteonthe

driveonwhichitwas

written.

F.Ifthe

drive passes all

the

checks

listed

above, it is operational. If not, review

Section

II.

1.9 INTERFACE

CONNECTIONS

Signal

connections

for

the

drive are

made

via a

user-supplied

50-pin,

flat

ribbon

connector

(3M

Scotchflex

3415). This

connector

mates

directly

with

the

circuit

board

connectoratthe

rearofthe

drive. TheD.C.

power

connector

is a six-pin

connector

(Amp

Mate-N-Lok

Part

Number

1-480270-0),

which

mates

with

the

connectoratthe

rearofthe

drive.

Thesignal

connector

harness

shouldbeof

the

flat

ribbon

ortwisted

pair

type, havea maximum

length

of

ten

feet,

and

have a

22-to-28

gauge

conductor

compatible

with

the

connector

thatistobeused.

Power

connections

should

be

made

with

18-AWG cable, minimum.

1.10

MOUNTING

THE DRIVE

The drive has

been

designedtomountinany

plane,

Le.:

upright, horizontal,orvertical. The

only

restrictionisthat

the

printed

circuit

board

sideofthe

chassis

mustbeuppermost

when

the

drive is

mounted

horizontally.

Eight

holes

are

provided

for

mounting:

twooneach

side

and

fouronthe

bottom

of

the

housing

(see Figure 1-1). The

two

on each

side

are

tapped

for

8-32

screws. The

four

mounting

holesonthe

bottom

require

8-32

thread

forming

screws.

Optional

straps

areavailabletopermit

attaching

two

drives

together

for

installationinstandard

width

drive openings.

1-5

---

0"

~-

°

F_}-

0r.!l\'l.

~1P.iI1r=--'t1

13.33

[(

J I

~-

-··------8.550----~

e

~

..

+

6-32 THO THRU 4 PL

(2

EA.

SIDE)

I---r-'-~

-,

8.00

.149

DIA. TOP X

.156

DIA.

BOnOM

X

.430DP.

4 PL

I

L----7.50---~.1

t

1

..

::

0

NOTES:

DIMENSIONS

GIVENININCHES.

1.10.1

Hardware

Figure

1-1

TM848

Disk

Drive

Mounting

Configuration

The

driveismanufactured

with

certain

critical

internal

alignments

that

mustbemaintained.

Hence,

it

is

important

that

the

mounting

hardware

does

not

introduce

significant

stress

on

the

drive.

A

three-part

mounting

schemeisrecommended.

Any

mounting

schemeinwhich

the

driveispart

of

the

structural

integrityofthe

enclosure

may

cause

equipment

operating

problems

and

should

be

avoided.

In

addition,

the

mounting

scheme

should

allow

for

adjustable

brackets

or

incorporate

resilient

memberstoaccommodate

tolerences.

1.10.2

Dust

Cover

The

designofan

enclosure

should

incorporateameanstoprevent

contamination

from

loose

items

e.g.,

dust,

lint,

and

paper

since

the

drive

does

not

haveadust

cover.

1.10.3

Cooling

System

Requirements

Heat

dissipation

fromasingle

driveisnormally

30

watts

(102)

Btu/Hr.)

under

high

line

conditions.

When

the

driveismounted

so

that

the

components

have

access

to

the

free

flowofair,

normal

convection

cooling

allows

operation

over

the

specified

temperature

range.

When

the

driveismounted

in a

confined

environment,

air

flow

mustbeprovidedtomaintain

specified

air

temperatures

in

the

vicinityofthe

motors,

the

circuit

board,

and

the

diskette.

1.11

DISKETTE

CARE,

HANDLING,

AND

STORAGE

It

is

important

that

the

diskette

be

cared

for,

handled,

and

stored

properlysothat

the

integrityofthe

recorded

dataismaintained.Adamagedorcontaminated

diskette

can

impairorprevent

recovery

of

data,

and

can

resultindamagetothe

read/write

headsofthe

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

surfaceofthe

diskette

with

fingers.

3.

Insert

the

diskette

carefully

into

the

drive

until

the

backstopisencountered.

4.

Do

not

bendorfold

the

diskette.

Ei.

Put

the

diskette

into

its

jacket

when

it is

not

in use.

6.

Store

the

disketteattemperatures

between1DoC

and 52°Cor50°F

and

125°F.

1.12 WRITE PROTECT The drive is

equipped

withaWrite

Protect

Sensor

Assembly.This

sensor

operatesinconjunction

with

a

diskette

that

has a

slot

cutinthe

protective

jacket.

When

the

slot

is uncovered,

the

disketteiswrite

protected.

The

slot

mustbecoveredtowriteonthe

diskette.

An

option

is available on

the

board

for

defeating

the

write

protect

sensor.

1.13 OPERATION

OF

THE DRIVE

The drive

consistsofthe

mechanical

and

electrical

components

necessarytorecord

andtoread

digital

dataona

diskette.

User-providedD.C.

powerat+24

volts

and+5voltsisrequired

foroperation

of

the

drive.

1.14 ORGANIZATION

OF

THE DRIVE

All

electrical

subassembliesinthe

drive

are

constructed

with

leads

that

terminate

in

multipin

connectors,

enabling

the

individual

assembliestobe removed.

The

heads

are

connectedtothe

circuit

board

via

cables

that

terminate

in five-pin

female

connectors

and

their

associated

male

sockets

that

are

located

in

close

proximity

to

the

read/write

data

electronics. Interface

signals

and

power

are

provided

via

connectorsatthe

rearofthe

drive.

1.15

COMPONENTS

OF

THE DRIVE

The drive

consistsofsix

functional

groups:

'1.

Index

Pulse

Shaper

2.

Drive

Status

Logic

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

diagramofthe

drive.Itshouldbereferredtoin

conjunction

with

the

following

sections.

The

datainthe

ensuing

figuresisprimarily

representedinsimplified

form.

1.15.1

Index

Pulse

An

index

pulseisprovidedtothe

user

system

via

the

index

pulse

interface

line.

The

index

circuitry

consistsofan

indexL.E.

D.,anindex

phototransistor,

andapulse

shaping

network.Asthe

index

hole

in

the

disk

passesanindex

L.E.D.

phototransistor

combination,

light

from

the

L.E.D.

strikes

the

index

phototransistor,

causingitto

conduct.

The

signal

from

the

index

phototransistorispassedonto

the

pulse

shaping

n~twork,

which

producesapulse

for

each

hole

detected.

This

pulseispresentedtothe

useronthe

index

pulse

interface

line.

1.15.2

Drive

Status

Logic

There

are

five

drive

status

logic

lines:

Write

Protect,

Track00Sensor,

Two-Sided

Ready

and

Disk

Change.

A.

Write

Protect

A

write

protect

signalisprovidedtothe

user's

system

via

the

write

protect

interface

line.

The

write

protect

circuitry

consistsofa

write

protect

sensor

and

circuitry

that

routes

the

signal

thatisproduced. Whenawrite

protected

disketteisinsertedinthe

drive,

the

sensorisactivated

and

the

logic

disables

the

write

electronics

and

supplies

the

status

signaltothe

interface.

B.

Track

00

Sensor

The

levelonthe

Track

00

interface

line

is a

functionofthe

positionofthe

head

assembly.

When

the

headispositionedatTrack00and

the

stepper

motorisat

the

home

position,atrue

(low) level

signalisgeneratedatthe

interface.

C.

Two-Sided

Disk

This

signalislow

(true)

when

the

driveisselected

and

has

detected

the

presenceofthe

Index

Two

holeinthe

diskette

currently

installed.

D.

Ready

This

signalistrue

when

Drive

Selectislow

(true)ifthe

spindle

driveisuptospeed

and

the

driveisreadytoread

and

write.

E.

Disk

Change

This

signalistrue

when

Drive

Selectislow

(true) if

the

diskette

lever

has

been

movedtothe

open

position

after

the

select

went

false.

1-8

1.15.3

Spindle Drive System

The spindle drive system consists of a spindle assembly driven through a drive belt by a brushless D.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

is

false (high), the drive motorisallowed to come up to speed.

READY

CONTROL

INDEX

LOGIC

DISK

CHANGE

TWO SIDED

WRITE PROTECT

TRACK

00

IN USE

SIDE SELECT

HEAD CARRIAGE

DRIVE SELECT

AND STEPPER BAND

ASSEMBLY

SPINDLE

MOTOR

CONTROL

MOTOR

CONTROL

WRITE GATE

WRITE

WRITE DATA

LOGIC

CURRENT

SWITCH

READ READ DATA

LOGIC

DIRECTION

STEPPER

MOTOR

CONTROL

STEP

Figure

1-2

TM848

Disk Drive Functional Block Diagram

1.15.4

Positioner Control

The head positioning system uses a bipolar-driven motor drive, which changes

one

phase for each track advancement of the read/write carriage. In addition to the logic necessary for motor control, a gateisprovided that inhibits positioner motion during a write operation.

1.15.5 Data Electronics Information can be recorded

on

the diskette by using a double-frequencycode. Figure

1-3

illustrates

the magnetization profiles

in

each bit cell for the number sequence shown for FM recording.

1-9

BIT

PATTERN----,

BIT

CELL""""

I 1 I 1

I I I

WRITE

DATA

o

I

1

I

C D

ic

D IC C I

D

C

ICC

D

1

I

I I I

I I I I I I

I I I

\:f.=k:1

,-,t;fl:f

~t:A1

I f I

MAGNETIZATION

1:

1

I I -

~

.

~

--'I

I

~

I I

IIIIIIIIIII~II

M~NEnCELEMEN~

~

I

r--rTt4

I I

Figure 1-3

FM

Recording

Magnetization

Profiles

The

erase

gaps

provide a

guard

band

on

either

sideofthe

recorded

track.

All

signals

requiredtocontrol

the

data

electronics

are providedbythe

user

system

and

are

shown

in

the

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

dataissenttothe

user

system

via

the

Read

Data

interface

line.

A.

Data

Recording

The

write

electronics

consist

ofaswitchable

write

current

source, a

write

waveform

generator,

an erase

current

source,

the

trim erase

control

logic, and

the

head

selection

logic

(see

Appendix

I).

The

read/write

windingonthe

head is

center-tapped.

Duringawrite

operation,

current

from

the

write

current

source

flowsinalternate

halvesofthe

winding,

under

controlofthe

write

waveform generator.

The

conditions

required

for

recording,

i.e.

drive ready

must

be

established

by

the

user's

system, as follows:

1.

Drive

speed

stabilization

occurs

700

milliseconds

after

the

drive

motor

is started.

2.

Subsequenttoany

read/write

operation,

the

positioner

must

be

allowedtosettle. This

requires18milliseconds

maximum

after

the

last

step

pulse

is initiated,

i.e.,3milliseconds

for

the

step

motion

and

15

milliseconds

for

settling.

3.

The

foregoing

operations

can be overlapped, if required.

Figure

1-4

illustrates

the

timing

diagram

forawrite

operation. At t =0,

when

the

unit

is ready,

the

write

gate

interface

line

goes

true. This

enables

the

write

current

source.

Write

current

is

switched

via

the

write

current

switch

interface

linetoa

lower

valuebythe

user's

controller

at

Track 43.

1-10

The Trim Erase

control

goes

true

190

microseconds

after

the

Write

Enable

interface

line

since

the

trim erase

gaps

are

behind

the

read/write

gap. It

shouldbenoted

that

this

value is

optimized

between

the

requirementsatTrack00andatTrack

76,sothat

the

effectofthe

trim

erase

gaps

on previous

information

is minimized.

Figure

1-4

shows

the

informationonthe

write

data

interface

line

and

the

outputofthe

write

waveform

generator,

which

togglesonthe

leading

edgeofevery

write

data

pulse.

A maximum

of4microseconds

between

write

gate

going

true

and

the

first

write

data

pulse

is

only

requirediffaithful

reproductionofthe

first

write

data

transition

is signifcant.

At

the

endofrecording,atleast

one

additional

pulseonthe

write

data

line

mustbeinserted

after

the

last

significant

write

data

pulsetoavoid

excessive

peak

shift

effects.

3.

10MAPEAKTO PEAK, TRACK 0 TO

TRACK42; 7.5 MAPEAK

TO

PEAK,

TRACK

43

TO TRACK 77.

4.

2 USEC

MINIMUM

4 USEC MAXIMUM

I

NOTES:

1.

T = 0 =

700

MILLISECONDS

AFTER DRIVE MOTOR

STARTS OR

20

MILLISECONDS

AFTER LAST STEP

PULSE, WHICHEVER IS THE LATEST TIME.

2.

UNSYCHRONIZED

Figure

1-4

Write

Operation

Timing Diagram

NOTE 2

I

~

I

~50usec""

I I

~-""""""-----""---"""~:;-"'I~

~---tl----;---+----

........-

.......

-~

.......

I

~~

I I

WRITE WAVEFORM GENERATOR

WRITE

CURRENT

INTERNAL WRITE BUSY

TRIM ERASE

WRITE GATE

The

durationofa

write

operation

is from

the

true

going

edgeofwrite

gatetothe

false

going

edge

of

erase. This is

indicatedbythe

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 usedtoisolate

the

read

amplifier

from

the

voltage

excursion

across

the

head

duringawrite

operation. The

side

select

is usedtoenable

oneofthe

read/write/erase

heads.

Thedrive

must

be in a ready

condition

before

readingcan begin.As

with

the

data

recording

operation,

this

ready

condition

must

be

established

by

the

user

system. In

addition

to

the

requirements

establishedinthis

section, a periodof100

microsecondsisnecessary

after

a trim

erase

operation

occurstoallow

the

read

amplifiertosettle

after

the

transient

causedbythe

read

switch

returning

to

the

read mode.

1-11

The

output

signal from

the

read/write

headisamplifiedbya read

preamplifier

and

filteredbya low-

pass

linear

phase

filtertoremove

noise

(see Figure 1-5). The

linear

output

from

the

filter

is passed

to

the

differentiator,which

generates

awaveform

whose

zero

crossovers

correspondtothe

peaksofthe

Read signal. This signal is then fedtothe zero crossing detector and digitizer.

LINEAR OUTPUT FROM FILTER

OUTPUT FROM DIFFERENTIATOR

READ DATA INTERFACE

t

==

0

Figure 1-5

Read Timing Diagram

Note

T= 0 is

definedas250

milliseconds

after

drive

motor

starts,or20

milliseconds

afterastep

command,or100

microseconds

afterterminationofwrite

busy,

whicheveristhe

latest

time.

The

zero

crossover

detector

and

digitizer

circuitry

generatea200

nanosecond

read

data

pulse,

correspondingtoeach

peakofthe

read signal. The

composite

read

data

signal is

senttothe

user

system via

the

read

data

interface

line.

1.16 INTERFACE 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

lengthisten

feet.Itis

recommended

that

the

interface

cable

be flat ribbon

cable

that

has a

characteristic

impedenceof100

ohms.

1.16.1

Interface

Connector

Pin Assignments, P13

The

interface

connector

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

1.16.2

Power

Connector

Assignments

The

power

connector

assignments

are listed in Table 1-4.

1-12

TABLE

1-3

INTERFACE

CONNECTOR

ASSIGNMENTS

Ground

---

1

3

5

7 9

"11

'13

"15 "17

'19

:21

:23

:25

27

29

31 33

35

37

39

41 43 45

47

49

Number

2

4

6

8

10

12

14

16

18

20

22 24 26 28

30

32

34

36

38

40

42

44

46

48

50

Signal

Write

Current

Switch

Motor

Off

Control

1

Motor

Off

Control

2

Motor

Off

Control

3

Two

Sided

(option)

(Model

TM848-2

only)

Disk

Change

(option)

Side

Select

(Model

TM848-2

only)

ActivityIndicator

(option)

Head

Load Index Ready Motor

Off

Control

4

Drive

Select1(Side

Select

Option,

TM848-2

only)

Drive

Select2(Side

Select

Option,

TM848-2

only)

Drive

Select3(Side

Select

Option,

TM848-2

only)

Drive

Select4(Side

Select

Option,

TM848-2

only)

Direction

Select

(Side

Select

Option,

TM848-2

only) Step Write

Data

Write

Gate

Track

00

Write

Protect

Read

Data

Alternate

I/O

Alternate

I/O

1-13

TABLE 1-4

POWER CONNECTOR PIN

ASSIGNMENTS

1

6

3

2 5

1.17 TERMINATED LINES

Supply

Voltage

24VD.C.

Return Return Return

5V

D.

C.

1.17.1

Input

Line

Terminations

From Removable Resistor Pack

The drive

has

the

capabilityofterminating

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

lines

are

individually

terminated

througha150

ohm

resistor

pack

thatisinstalledinthe

dip

socket

locatedatintegrated

circuit

location

RP1. In a single-drive system,

this

resistor

pack

shouldbeinstalledtoprovide

the

proper

terminations. In a multiple-drive system,

only

the

last drive

on

the

interfaceisto

be terminated. All

other

drivesonthe

interface

must

have

the

resistor

pack

removed (see

Figure

1-6).

1.17.2 Drive

Select

The

Select

lines

provide

a meansofselecting

and

deselecting

a drive. These

four

Iines·-OS1

through

DS4--allow

independent

selectionofuptofour

drives

attachedtothe

controller.

When

the

signal

logic

level is

true

(low),

the

drive

electronics

are

activated

and

the

drive is

conditionedtorespondtoStep

orto

Read/Write

commands.When

the

signal

logic

level isfalse(high),

the

input

control

lines

and

the

output

status

lines

are disabled.

The drive

select

addressisdetermined

by

a movable

shorting

plug

installed

on

the

circuit

board.

Select

lines

one

through

four

provide a

meansofdaisy

chaining

a maximumoffour

drivestoa

controller.Onlyonelinecan betrue(low) at a time.An undefined operation might result iftwo

or

moreunits

areassigned

the

sameaddressoriftwoormoreselect linesare in the true(low) state simultaneously (see

Figure

1-7). A

select

line

must

remain

stableinthe

true

(low)

state

until

the

execution

if a

Step

or

Read/Write

commandiscompleted.

1.17.3 Program Shunt

The program shunt is AMP Part Number 435704-8. The program shunt positions are programmed by cutting

the

particular

shunt. The program

shunt

is installed in a

dip

socket. At

the

user's option,

the

program

shunt

may

be removed

and

replacedbya

dip

switch. Pins 8 and 9ofthe

program

shunt

are

not

used.

See

Table 1-5

fora

listingofthe

program shunts.

1-14

R133

o

P6

P14

M2

00

o o

00

CI:(J)

CI:O

~P4

~P5

M3

0-0

o

M4

2SCH)

DC

00

RI

TP11 G 0 TP12

ALTERNATE TEST POINT, INDEX TRIGGERING

R33

I

00

y

~

NP

@O~S2

OS1

g~O:

WP

P2

P3

Pi0

Pi

P11

P12

TP5

t

TP4ooopT6

TP2

TP1

1

o

~o

TP3

P8

pg

00

DSi

1b

0

000S2

2b

0 000S3

3b

0

000S4

4b

0

o

OTP8 OTP10

gOL

P7

MC3

2 j

MC2~C'gMC1

S2

0

IT

S

1

D 0 S2

o

C g

MC4g

RP1

o

TP9

P13

50

TP7

o

......

I

......

01

Figure 1-6

Circuit Board Assembly

D.C. POWER

MOTOR OFF

CONTROL

DRIVE SELECT

---l

r-

500

NSEC. MINIMUM

0,8 SEC

MAXIMUM

..

_

STATUS

OUTPUTS VALID

-

........

"'1--

500

NSEC'MINIMUM

---.:.J

L 1 USEC MINIMUM

~-------

..

DIRECTION

SELECT

I---

550

USEC.

MINIMUM'

4 USEC.

MAXIMUM

I--

100

USEC. MAXIMUM

U3 MILLISECONDS

MINIMUM

1 USEC. J

l--

MINIMU~~

I---

100

NSEC MINIMUM.

...

---------

....

--

...

~~

.-U

I---

18

MSEC. MINIMUM

1--------_

......

-....

..-------'\,,...---.

~

VALID

READ DATA

WRITE DATA

SIDE SELECT

WRITE GATE

Figure 1-7

General Control and Data Timing Requirements

1-16

1.18

OS

AND

HL

POWER SAVE OPTIONS

The

driveis

setupwith

theHLoption

in. This

stepper

power

from head load

line

option

supplies

power

to

the

stepper

motor

when

the

head load

line

goes

low

(true),

which

resultsinlower

stand-by

current

consumption.

As

shipped

from

the

factory, HL is installed

but

will remove

power

from

the

stepper

motor

when

the

driveisdeselected.

There

should

be a

20

millisecond

wait

after

a Drive

Select

command

is given in

ordertoallow

the

step

motor

electronicstosettle.

The

stepper

power

from drive select,

OS

option,

allows

the

usertoremoveD.C.

power

from

the

stepper

motor

using driveselect,

which

resultsinlower

stand-by

current

consumption.

This

option

is

implemented

by

installing

OS,

and

cutting

HL.

1.19 USER SELECTABLE OPTIONS

The

descriptionofuser

selectable

options

should

be used in

conjunction

with

the

following

list

of

options

that

are

available

for

model

numbers

TM848-1 and

TM848-2

(see Table 1-5).

TABLE 1-5

OPTIONS

AS

SHIPPED

TRACE

Shunt/Pin

Not

OPTION

DESIGNATOR

Locations

Installed

Drive Se

lect

DS1-DS4

DS1

Side

Select

Options

using Drive

Select

1B-4B

X

In Use, Drive

Select

Z

U3,1-16

X

In Use,

Head

Load

Y

X

Ready

Alternate

Output

Pad

R

U3,

7-10

X

Radial Ready

RR

X

Ready,

Modified

RM

X

Radial

Index

RI

X

Index,

Alternate

Output

Pad

I

U3,6-11

X

In Use,

Alternate

Output

Pad

0 X

Diskette

Lever

Lock

Latch

Option

DL X

Disk

Change

DC X

Two-Sided

Diskette

Installed

2S X

Stepper

Power

from Drive

Select

OS

X

Stepper

Power

from

Head

Load

Line

HL

U3,2-15

X

Head

Load

Alternate

Output

Pad

C

X

Radial

Head

Load

Signal

A

U3,3-14

X

Radial

Head

Load Signal

B

U3,4-13

X

Radial

Head

Load

Signal

X

U3,5-12

X

I

nhibit

Write

When

Write

Protected

WP

X

Allow

Write

When

Write

Protected

NP X

Head

Side

Select

Options

S1-S3

S2

Spindle

Motor

Control

Options

M1-M4

M1,

M3

M2,

M4

Motor

Control

Select

MC1-MC4

MC1

1-17

1.19.1

Drive

Select

OS

1-DS4

This

option

allows

the

usertodaisy

chain

uptofour

drives,

andtoenable

one

driveatat

time.

Drive

selectisimplementedbyshorting

oneofthe

four

connections,

usingashorting

plug.

The

drive

comes

equipped

from

the

factory

with

OS1

installed.

All

outputs

are

gated

with

drive

select,asset-up

at

the

factory.

1.19.2

Side

Select

Options

Using

Drive

Select

18--48

This

option

allows

the

usertoselect

the

headtobe

used

with

drive

select.

Side

Select

options

are

implementedbyremoving

the

shorting

plug

from

the

DS1-DS4

option

pads,

installing

Pins18-48,

and

connecting

the

shorting

plugtothe

desired

18-48

pins. S2

shouldbeetch

cut,

and

S3

installed

(see

Section

1.18).

1.19.3 In

Use

From

Drive

Select

(Z)

This

option

allows

the

usertoenable

the

activity

L.E.D.

when

the

driveisselected.

In

Use

From

Drive

Selectisfactory

installed.

1.19.4 In

Use

From

Head

Load

(Y)

This

option

allows

the

usertouse

the

head

load

linetoenable

the

Activity

L.E.D.

In

Use

From

Head

Loadisimplemented

by

punching

out

OptionZbetween

Pins 1

and

16ofU3. A

jumper

must

be

installedatlocation

Y.

1.19.5

Ready

Alternate

Output

Pad

(R)

This

low

going

signalisderivedbygating

the

internal

ready

and

drive

selecttogive

the

controller

a

true

(low)

ready

statusofthe

drive

.

. The

Ready

Alternate

Output

Pad is

factory

installed.

1.19.6 Radial

Ready

(RR)

This

option

allows

the

usertomonitor

the

ready

statusofall

drives

without

selecting

them.

This

option

cannot

be

used

concurrently

with

individual

motor

control

lines

for

each

drive.

(see

Figure

1-8).

Radial

Readyisimplementedbypunching

out

OptionRbetween

Pins 7

and10of

U3,byetch

cutting

RR,

thenbyrunningawire

from

U4, Pin 3tothe

desired

alternate

output

lines4,6,8,

and

24.

1-18

RI4

+5

~99

150

+5V

ETCH CUT

PROGRAM

SHUNT

PINS

7-10

ARE

OPENED

/'

OREDY+

RADIAL

READY

STATUS

TO USER

CONTROLLER

RM

'9

ETCH CUT

~-~~4

~

IREADY

-

,--

.........

--

~'3_SE_L_+_.

---~'--o-------'

RR

Figure

1-8

Radial Ready

Installation

Note

MC1

through

MC4

cannot

be used as radial

motor

control

when

using

this

option.

1.19.7

Ready,

Modified

(RM)

This

option

allows

the

drivetowriteonthe

upper

surfaceofa

single-sided

diskette. It

prevents

the

drivefrom

making

Ready

become

false

when

the

upper

surfaceofa

single-sided

diskete

isselected.

To

implement

this

option,

connectajumperatthe

RM pads.

1.19.8

Radial

Index

(RI)

This

option

uses

the

alternate

I/O

lines

for

radial

index

lines.This

option

allows

the

userto

monitor

the

indexofeach

drive

independentofdrive select. This

option

cannot

be used

concurrently

with

radial

ready,

or

with

independent

motor

control.

Radial

Indexisimplementedbyremoving

the

shunt

bridge

at U3, Pins 6

and

11, by

etch

cutting

radial

index,

andbyrunningawire

from U4, Pin6,to

the

appropriate

alternate

I/O

lines.IfuseofMC1 is

desired,

interface

line

20

may be used as

one

index

line. In

this

case,

the

shunt

pack, U3, 6-11,

remains

intact

on

one

drive, (see

Figure

1-9).

1-19

R.99

150

+~v

~

R\~

4.71(.

DRSEL + .... 5

INDEX

+

R\

D--e--=i

4

RADIAL INDEX STATUS TO USER

CONTROLLER

PROGRAM

SHUNT

PINS

6-10

ARE OPENED

/

1,l~"OI\

INDEX

QQ]

'LOCo

+5V

1/\

~\

'~

'\

ET_CH

CUT

\

t"f;,V

~

2-

[4

Q--

~It_-3r2!~X:------~

~

rr---, \ \

1fC

2.

OeD

~

\\

CD

','oMC

~

fM>

't'C4

Figure

1-9

Radial I

ndex

Installation

1.19.9

Index

Alternate

Output

Pad (I)

The

internal

index

pulse is

gated

with

drive

selecttogivealow

true

signalatPadI.This

option

should

be

left

connected

for

the

controllertoreceive

the

index

pulse.

See

Radial

Index

for

other

usesofthis

line. The

Index

Alternate

Output

Pad

optionisfactory

installed.

1.19.10 In Use

Alternate

Output

Pad (D)

This linemaybeused

to

latchalever

lock

solenoid,

which

isan

optional

feature. A

low

(true)

command

is

sentbythe

controllerto

Pin16of

interface

connector

P13.Then

this

signal is

used

with

drive

select

to

latch

the

locking

solenoidbypulsing

drive

select

with IN USE low. The

solenoidisunlatched

when

drive

selectispulsed

and

IN

USE

is high.

To

implement

this

option,

locate

option

pads D

and

DL. Install

jumpersatthese

locations.

1.19.11

Diskette

Lever

Lock

Latch

Option

(DL)

This

option

is used in

conjunction

with

in use,

alternate

output

pad.

To

implement

this

option,

locate

option

padsD

and

DL.lnstall

jumpersatthese

locations

(see

Section

1.18).

1.19.12

Disk

Change

(DC)

This

output

is usedtoindicatetothe

controller

thatadisk

change

has

been

made. The

internal

signal

is

gated

with

driveselect.When

the

lever

isopened,

the

disk

change

line

goes

low

(true),

and

stays

low

until

the

trailing

edgeofthe

1.19.13 Two-Sided

Diskette

Installed

(2S)

When a

two-sided

diskette

is installed,

internal

circuitry

gates

this

signal

with

driveselect,

and

sends

a

low

(true) signaltothe

controller,

which

means

thatadouble-sided

disketteisinstalled

(index hole

two

is present).

The Two-Sided

Diskette

Installed

optionisfactory

installed.

1-20

1.19.14

Stepper

Power

From Drive

Select

(OS)

This

option

allows

the

usertoremoveD.C.

power

from

the

stepper

motor

using

drive

select,

which

resultsinlower

stand-by

current

consumption.

The

Stepper

Power

From Drive

Select

optionisimplemented

by

installing

OS,

and

cutting

HL.

1.19.15

Stepper

Power

From

Head

Load

Line

(HL)

This

option

supplies

powertothe

stepper

motor

when

the

head load line

goes

low

(true).This

results

in

lower

stand-by

current

consumption.

This

optionisfactory

installed.

OS

must

be removed

for

proper

operation.

1.19.16

Head

Load

Alternate

Output

Pad

Option

C

This

option

allows

the

userto

loadand

unload

the

headload

solenoid

(optional) and,

along

with

the

HL

and Y options,

enables

the

stepper

motor

and

lights

the

Activity

L.E.D.,

respectively.

Head

load is

accomplished

by

connecting

both

option

padsClocated

near

interface

connector

P13.

1.19.17 Radial

Head

Load

Signal,

Options

A,

B, and X

By

selectionofthe

appropriate

combinationofthe

A,B,or

Xjumper,

the

user

can use

either

Drive

SelectorHead

Loadtoactivate

the

Activity

L.E.D.

and

Lever

Lock

Solenoid

option

(see

Figure

1-10).

DIR±..._

OIl.~L..+

10 SlOE.

\-

W';ll..-

U,>

c==

I(,cr!!:'

0,

y

r#)O.O'----

__

--<>

POR.-

(i>

POR-

L504

D~

':iTI>El<.l+

H~;=r---

....-_uS_'O_z,

----ll

~getDID

,.--______

POR+

+SV

+5V

+ov

I~O

\'::>0

R4

RO

';f,~

5iDE

~--<1;i=:)'O'------------t-t--+_···_·,

~:14

,,"'_---O-,5~1

----------1--+-+-------'

ISO

tr~'------"'<1~

,.......L';,OZ.

11:1'.03

z.

US

)-'-1

---------+----~

+5V

14

I~

U~:,

4e04

5

Figure

1-10

Radial

Head

Load Signal

1.19.-18

Inhibit

Write

When

Write

Protected

(WP)

This

option

is usedtolock

out

the

write

gate

whenawrite

protected

diskette

is installed.

Inhibit

Write

VVhen

Write

Protectedisfactory

installed.

1.19.19

Allow

Write

When

Write

Protected(NP)

This

option

allows

the

controllertowriteonany

diskette,

whetherornot

is is

write

protected.

1-21

Note

This

option

does

not

stop

the

write

protect

signal from being

sentonthe

interface

line.

This

optionisimplementedbycutting

WP,

andbyinstalling NP.

1.19.20

Head

Side

Select

Options

S1--S3

This

option

allows

headstobe

selectedbyside

select, driveselect,

orthe

direction

control

signal.The

drive

comes

with

side

select, S2, installed.

To

use

the

drive

select

linetoenable

the

heads,

cut

S2

and

install S3

along

with

the

proper

18-48

jumper

that

is used with S3 (see

18-48).

For

head

selection

using

Direction

Select,

cut

S2, and install

S1.

1.19.21

Spindle

Motor

Control

OptionsM1--M4

M1 is usedtoenable

the

motor

off

delay

timer. When

this

jumper

is installed,

the

drive

motor

is

enabled

and

disabledbyeither

the

drive

select

(M3)orhead load (M4) commands. A

20-second

turn

off

delayofthe

spindle

motorisactivated

on

the

trailing

edgeofthe

controlling

signal.

M2

is used

for

radial

motor

control

independent

ofthe

motor

control

functions

installed

withM1,

M3,

and M4. M2

shouldbein

ifthe

user

wishestoenable

the

drive

motor

continuouslyorto

use

the

radial

motor

on

line MC1-MC4. M3

is usedtocontrol

the

drive

motor

using

drive

select.

When

the

drive

select

line

goes

low

(true),

the

drive

motor

comesupto

speed

in less

then

500

milliseconds

and

becomes

ready in less

than

700

milliseconds.

After

the

drive

select

line

goes

false (high),

the

motor

will run

for

20

seconds. To

implement

this

option, install a

jumperatlocation

M3.

For

correct

operationofM3, remove M4.

M4

is usedtostart

the

drive

motor

using

the

head load

interface

lines.

When

the

head load

line

goes

low(true),

the

drive

motor

comesupto

speed

in less than

500

milliseconds

and

becomes

readyin less

than

700

milliseconds.

After

the

head load line

goes

high (false),

the

motor

will run

for20seconds.To

implement

this

option, remove

M3

for

correct

operationofoption

M4.

1.19.22

Motor

Control

Select

Options

MC1--MC4

This

option

is usedif

the

drive

motoristobeenabled

independentofdrive

selectorheadselect.

When

these

lines are

low

(true),

the

motor

is off. The drive

comes

without

this

option

installed. This

option

does

not

operate

the

time

out

delay

circuit.

To

implement

this

option

that

controls

the

drive

motor

usingan

MCx

line, install

the

appropriate

MC 1-

MC4

jumper.

When

using

this

option,

M2

must

be installed. If

the

motor

turn

off

delay

is desired,

the

delaycanbetriggeredbyDrive

SelectorHead

Load commands,

when

used in

conjunction

withM3or

M4.

1-22

SECTION

II

MAINTENANCE

CHECKS

AND

ADJUSTMENTS

2.

INTRODUCTION

This

sectionisfor

the

useofthe

OEM

Repair

Department.Itcontains

checks

and

adjustments

that

are

used

during

the

normal

lifeofthe

drive.

Before

applying

powertothe

driveordoing

any

checksoradjustments,

visually

inspect

the

drive

to

ensure

thatithasnomissingorbroken

parts.

The

following

equipmentisrequired

for

checks

and

adjustments:

1. A

dual-channel,

wideband

oscilloscope:

Tektronix

465orequivalent

2.

An

exerciserorsoftware

routine

capableofstepping

the

drivetoany

track,

selecting

the

upperorlower

head,

and

writing

a 1F,all

zeros

if FM,or a 2F, all

ones

if FM,

patternonthe

disk.

3. A

Phillips

screwdriver

4. A

setofAllen

wrenches

5.Aflat

blade

screwdriver

6.Ablank

diskette

7. An

alignment

diskette:

Dysan

360/2Aorequivalent

8.

Integrated

circuit

dip

clips,14and

16

2.1

SPINDLE

DRIVE

MOTOR

CHECKS

AND

ADJUSTMENTS

The

long-term

drive

motor

speed

adjustment

ensures

that

the

motor's

speediswithin

the

range

of

tolerance

specified.

The

motor

speed

specificationis360

RPM ±

1.25

percent.

2.1.1.

Long-Term

Drive

Motor

Speed

Checks

and

Adjustments

A.

Preliminary

checks

required:

Verify

power:

+24VD.C.±10

percent

+5VD.C.

± 5

percent

B.

Apply

powertothe

drive.

C.

Activate

the

drive

motoronthe

interface

line.

D.Insertawork

diskette.

2-1

E.

Setupthe

oscilloscope, as follows:

Voltage: 2

volts

per

division

Time Per Division:

20

milliseconds

Trigger: Negative,

ChannelA,R33

Note

For

the

TM848-1 single-sided drive,

trigger

offofR33.

For

the

TM848-2

double-sided drive,

trigger

off of Test Point 12,

with

the

exceptionofazimuth,

which

must be

triggered

offofR33

(see Figure 2-1).

'

R133

MIg

0

8

M2

cr.

00

o

1ttttttttttttft

....

-.;.,;P6:.....-_-r-

P

,;"..,14

00

(I<Il (IO

~

..

P4

~P5

M3

C>O

o

M4

2S_

DC

00

RI

~

ALTERNATE

TEST

POINT,INDEX

TRIGGERING

0-3-0

NP

00

y

DSI

00&00

DS2

WP -

TPll0erz.,.

P2

P3Pl0

PI

PllP12

ffiffftf11TTiil

TP2

TPI

1

-

Jo

TP3

P8 P9

1i1iftttif

00

DSI

lb

0 00

DS2

2b

0

00DS3

3b

0

00DS4

4b

0

o

OTP8 OTP10

gDL

P7

00

P13

Figure

2-1

Circuit

Board Assembly

F.

Adjust

R133

until

a reading

of

166.667

millisecondsisachieved

from leading

edgetoleading

edgeofthe

index

pulses.

G.Ifthe

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

headatthe

oroper

radial

distance

from

the

hub

center

line,

ensuring

that

the

track

location isaccurate(seeFig;ure 2-2). This

adjustment

is necessary

only

after

servicingorif

diskette

interchange

problems

are suspected.

2-2

HUB CENTER LINE

TRACK 0

"---~---

TRACK

38

TRACK

76

Figure 2-2

Hub

Center

Line and Track Locations

2-3

2.2.1

Cats

Eye

Alignment

Check

A.

Setupan oscilloscope, as follows: Channel

A;

Channel

B: Ground Read Differentially: Time Base: External Trigger:

Test

Point2alternate

is Test

Point

4 on R30

Test Point 3

alternate

is Test Point 5 on R29

Test

Point

1

A plus

B,

B inverted

20

milliseconds

per

division

Test Point 11, negative trigger,

for

single-sided drives. Test

Point

12, negative trigger,

for

double-sided drives. R33 (end

closest

to

DS2), negativetrigger, isan

alternate

test

point

for

both

single-and

double-sided drives.

B.

Apply

powertothe

drive.

Note

TheTrack38radius is 2.8207 ± .0020.

Other

tracklocationsarecomputedbased upon48TPI.

C.

Select

the

driveatthe

interface.

D.

Insert

the

alignment

diskette

into

the

drive.

E.

Select

Head 00,

the

lower

head.

F.

Seektoand

observe Track38for

Cats

Eye

alignmentofthe

lower

head.

G.

Adjust

the

oscilloscopetoobserve a

Cats

Eye

pattern

(see Figure 2-3).

Equal amplitude. Lobes

shownat100

percentonTrack

38.

Time Scale:

20

ms

Figure 2-3

Cats Eye Pattern

2-4

H.

Verify

that

the

smallerofthe

two

Cats

Eye

lobesisnot

less

than

75

percentinamplitude

of

the

other

one.

The

calculation

is:

ampofsmaller

lobe

X

100

ampoflarger

lobe

I.

Step

the

drivetoTrack

00, then,

stepitbacktoTrack

38.

J.

Reverify

the

Cats

Eye pattern.

K.

Step

the

drivetoTrack

76; then,

stepitbacktoTrack

38.

L.

Reverify

the

Cats

Eye pattern.

M.

On

double-headed

drives,

select

the

upper

head (Head 01)

and

repeat

StepsFthrough

L.

N.Ifanyofthe

checks

listed

above

does

not

meet

the

conditions

statedinStepH,the

head

carriage

must

be adjusted.

2.3 HEAD CARRIAGE

ADJUSTMENT

A.

Turn

the

two

position

retaining

screws

that

straddle

the

nylon

adjustment

cam

located

ben~ath

the

drive

until

the

cam

can be moved (see

Figure

2-4).

POSITION RETAINING SCREWS (2)

ADJUSTMENT CAM

Figure

2-4

Head

Module

Retaining

and

Cam

Screws

B.

Observe

the

Cats

Eye

pattern

from

the

head

thatisfarthest

outofalignment.

C.

Using a

flat

blade

screwdriver,

turn

the

adjustment

cam

until

one

Cats

Eye

lobeiswithin

75

percentoJthe

amplitudeofthe

other

lobe.

Note

Check

the

upper

and

lower

headsondouble-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

SENSOR

CHECKS

AND

ADJUSTMENTS

The

index

adjustment

changes

the

time

period

from

the

index

pulsetothe

startofthe

data.

The

adjustment

shouldbechecked

after

the

drive

has

been

aligned

(see

Section

2.1.1)orwhen

diskette

interchange

errors

are

suspected.

2.4.1

Index-to-Data

Burst

Check

A.

Apply

powertothe

drive.

B.

Select

the

drive.

C.

Check

the

spindle

speedofthe

drive

(see

Section

2.1).

D.

Setupan

oscilloscope

as

follows:

Trigger:

Read

Differentially:

Channel

A:

Channel

B:

Time

Base:

Single-sided

drives

trigger

on

right

leadofR33

(closest

to

DS2),

negative

edge;

double-sided

drives

trigger

on

Test

Point

12,

negative

edge.

A

plusB,B

inverted

Test

Point

2

Test

Point

3

50

microseconds

per

division

E.

Insert

an

alignment

diskette.

F.

SeektoTrack

1.

G.

Select

Head

00,

the

lower

head.

H.

Ensure

that

the

index-to-data

burst

occursat200

microseconds±100

microseconds

from

the

leading

edgeofthe

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

Head00or

Head01does

not

meet

the

specifications,

adjust

the

index

sensor

(see

Section

2.4.2.).

2-6

Time

Scale:

50

usee

per

division

Figure

2-5

I

ndex-to-Data

Burst

K.

When

both

index

measurements

on a

double-sided

driveorthe

one

index

measurement

on a

single-sided

drive

meet

the

specifications,

see

SectionH,check

the

index-to-data

burst

on

Track

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

be

adjusted

(see

Section

2.4.2).

2.4.2

Index

Sensor

Adjustment

A.

Loosen

the

index

sensor's

retaining

screw

located

on

the

undersideofthe

chassis

(see

Figure

2-6).

o

L:)

.J

o

INDEX SENSOR

'P\6~1f""""H--H----

RETAINING SCREW

Figure

2-6

Index

Sensor's

Retaining

Screw

and

Adjustment

2-7

B.

Adjust

the

index

sensor

withaflat

blade

screwdriver

until

the

index-to-data

burst

occurs

200

microseconds±100

microseconds

from

the

leading

edgeofthe

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

Pulse

Width

Check

The

index

pulse

widthisnonadjustable.Ifthe

index

pulse

widthisnot

within

specifications,

replace

theIndex

Sensor

Assembly.

A.

Setupan

oscilloscope

as

follows:

Channel

A:

Ground:

Time

Base: Voltage: Trigger:

To

appropriate

index

test

point,

see

Section2,Item

Number

1.

Test

Point

1

.5

millisecond

per

division

2

volts

per

division

Negative

leading

edgeofChannel

A,

appropriate

test

point.

B.

Ensure

that

the

negative

going

pulse

widthisbetween

1.0

and

2.3

milliseconds

(see

Figure

2-

7).

u u

~

1.8to2.3

milliseconds

Figure

2-7

Negative

Going

Pulse

Width

2.5 TRACK00SENSOR

CHECK

AND ADJUSTMENT

TheTrack00sensor

providesa signal

that

identifiesTrack00to

the

logic

electronics.A

Track00signal is

senttothe

controller

on Pin20of

the

interface.

A.

Apply

powertothe

drive.

B.

Load an

alignment

diskette

into

the

drive.

C.

Step

the

carriagetothe

radial

alignment

track, Track38(see

Section

2.2).

2-8

D.

Confirm

the

positionbyobserving

the

Cats

Eye pattern.

E.

Attach

ChannelAto

Test Point 10.

F.

Restore

the

carriagetoTrack 00,

and

ensure

that

the

Track00L.E.D.onthe

exerciser

turnson.

G.

SeektoTrack1,and

ensure

that

the

signalatTest Point10is high.

H.

SeektoTrack2,and

ensure

that

this

lineisloworin

transition.

I.

SeektoTrack3,and

ensure

that

this

line is low.

J. If

the

signal is incorrect, restoretoTrack00with

the

oscilloscope

attached

as above.

K.

Seek

outtoTrack2,and

loosen

the

two

retaining

screws

that

hold

the

Track00sensor

(see

Figure 2-8).

RETAINING SCREWS

Figure

2-8

Track

00

Sensor

L.

Push

the

sensor

toward

the

backofthe

drive, and

slowly

push it forward until

the

signal on

the

oscilloscope

just

goes

low

(true).

M. Tighten

the

retaining screws,

and

repeat

StepsEthrough

I.

N.

Verify

the

adjustment.

2.6 AMPLITUDE

CHECK

The

amplitude

test

checks

the

necessary read,

channel

amplifier/differential

output

voltage.

A.

RestoretoTrack

00

B.

Insertawork

diskette

and

write

a 2F, all ones, pattern on

the

lower

head.

2-9

C.

Connect

an oscilloscopetoTest Points 4 and5,using Test Point 1 as a ground.

D.

Set up an oscilloscope as follows:

Channel

A:

Channel

B:

Both Channels: Time Base: Trigger:

Test Point

4,

1 volt per division

Test Point

5,

1 volt per division A.C.coupled, Channels A and B added, Channel B inverted 50

milliseconds per division,

synchronize internally on Channel A

or

B

Automatic

E.

The minimum amplitude displayed on the scope should be no less than three

(3)

volts peak-to-

peak 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

not

contaminated.

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 Carriage

Assembly.

2.7 AZIMUTH CHECK

Azimuth is the angle

of

the

heads with respect to the track at

the

point of

the

read/write gap. Azimuth is

measured in minutes (one minute

=

1/60

degree).

A.

Set up an oscilloscope as follows:

Channel

A:

Test Point2,100

mV

per

division

Channel

B:

Test Point3,100

mV

per

division

Ground: Test Point 1

Both Channels:

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

Channel B inverted

Time Base: 1 millisecond

or

as required to display

the

pulse groups

Trigger: Leading edge of appropriate test point

(see Section

2,

Item Number

1)

B.

Insert an alignment diskette.

C.

Step

the

drivetoTrack

76'.

D.

Observe

the

following pattern. Figure 2-9depictsan optimum head alignment ofzero minutes of

azimuth error. This means that

the

Head Carriage Assembly is perpendiculartothe

track

being

read, 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 1

is less than

or

equaltoBurst2,and that Burst

4 is less

thanorequaltoBurst 3.

1 2

3

4

Figure 2-9

Optimum

Head

Azimuth

Alignment

E.

Figure

2-10

depicts

an azimuthofexactly

minus9,12,or18

minutes,

depending

upon

the

manufacturerofthe

diskette

used. This is

the

lower

limitofallowable

azimuth error.

Bursts

1 and 2 areofequal amplitude.Ifthis

signal is observed,

the

Cats

Eye

alignment

shouldbechecked

priortoany

corrective

action.

3'

1 2

4

Figure

2-10

Head

AzimuthofAcceptable

Lower

Limits

F.

Figure 2-11

depictsanalignmentofexactly

plus9,12,or18

minutes,

depending

upon

the

manufacturerofthe

diskette

used. Bursts 3 and 4 areofequal amplitude.This is

the

upper

limitofallowable

azimuth

error. If

this

signal is observed,

the

Cats Eye

alignment

shouldbechecked

priortoany

corrective

action.

G.

After

the

lower

head has been checked,

switchtoread on

the

upper

head and observe

the

azimuth pattern. Both

the

upper

and

lower

heads

shouldbewithin

the

specification.

2-11

2

3 4

1

Figure 2-11

Head Azimuth Alignment of Acceptable

Upper

Limits

Note

The head's azimuth is

not

adjustable.Itis suggested

that

the

drive be

senttoan authorized repair

centerora new Head assembly be installed. In

the

latter

case, all previous adjustments should be made again.

2.8 LOAD ARM ADJUSTMENT

This adjustment is made to ensure

proper

loadingofthe

head when

the

diskette

is engaged (see

Figure 2-12).

A.

Insert a

work

diskette

into

the drive.

B.

Turn the

diskette

leverto load

the

disk, and

seektoTrack00. There shouldbe aspaceof.015

inch minimum between

the

head load arm and

the

load plate.

C.

SeektoTrack 76, and ensure that a space of .015 inch minimum remains between

the

head

load arm and

the

load arm.

D.

Adjust

the

screw

located behind

the

head load cam until

the

foam

just

touches

the

platen.

E.

Inserta

work

diskette

and ensure

that

there is adequate space between

the

upperhead and

the diskette.

F.

The

upper

head should

not

hit

the

diskette

when inserting and ejecting it.

ADJUSTMENT SCREW

Figure 2-12

Load Arm Adjustment, Front View

2-12

SECTION

III

PRINTED

CIRCUIT

BOARD OPERATION

3.

INTRODUCTION

This

section

contains

the

interface

description

and

the

circuit

board

theoryofoperations

for

the

TM848

familyofdisk

drives. In addition,

Sections

3.1

and 3.2

contain

schematic

diagramsofthe

circuit

boards installed in

the

drive.

3.1

PHYSICAL DESCRIPTION OF THE CIRCUIT BOARD

The printed

circuit

board is

approzimately

12.50-inches long by 5.25-inches wide. Figure

3-1

contains

an illustrationofthe

placementoftest

points

and connectors.

R133

M18

0

g

M2

a:.

00

P6 P14

o

ffitttttttttffl

00

a:CIl a:c

~P4

~P5

M3

0-0

OM4

2SCH)

DC

00

RI

v

TP11 0 0 TP12

ALTERNATE TEST POINT. INDEX TRIGGERING

~I

NP

ooy

OS1Sg&S2

WP

TP5

t

TP4000pT6

P2

P3

P10

P1

P11P12

~

TP2

TP1

!

o

~O

TP3

00081

1b

0

000S2

2b

0

000S3

3b

0

00084

4b

0

P8

pg

9iffftttff

o

OTP8

OTP10

gOL

P7

00

P13

Figure

3-1

Printed

Circuit

Board

3.2 INTERFACE ELECTRONICS SPECIFICATIONS All interface signals are

TIL

compatible.

Logic

true

(low) is

+0.4

volt minimum. Figure 3-2 illustrates

the

interface

configuration. The maximum interface

cable

length is

ten

feet.

+

5V

+

TRUE

r--------,

I I

I

I I

L

7~6

~~E~U~~~~

TWISTED

PAIR

TRANSMISSION

LINE

~

10

FEET

74LS04OREQUIVALENT

+

TRUE

DRIVER

RECEIVER

Figure 3-2

Interface Configuration

3-1

Itisrecommended

that

the

interface

cablebeflat

ribbon

cable,

withacharacteristic

impedance

of

100

ohms.

Interface

connector

assignments

are

given

in Table 3-1.

3.3 INPUT

CONTROL

LINES

A.

DS1-DS4,

Select

Lines

Functional

Description

The

select

lines

(see

Figure

3-3) provide a

meansofselecting

and

deselecting

a drive. These

four

lines, DS1

through

DS4,

select

oneofthe

four

drives

attachedtothe

controller.

When

the

signal

logic

level is

true

(low),

the

drive

electronics

areactivated,

and

the

driveis

conditionedtorespondtoStep

or

Read/Write

commands.

When

the

logic

level is false (high),

the

input

control

lines

and

output

status

lines

are

disabled.

POR+

PII

"

L':>OO

r-1

15(o11.9f>

2.

D

100 I I

I I

~nVIT'(

I I L.E.O.

~I

VI

I

+Z4~ID'

I I LEVER

I I

LOC.~

2.

754(,,2.

I I

~NO\D

" I

I

2.7

L_J

PIZ,

'lEl'.D

t-------------~

LOAD

~LEt-.lOIO

DR':>E.l..-

U~

c==

llocr~\

01

t------'-Io

I)c~--

__

--oy

~-

J .

_\4

g~~

011>+

---+-+-+--

'il

!2.

e.

DIR+_

L':lI.q

+~V

+5V

1'50

R!:>

+sv

150 R4

Figure

3-3

Select

Lines

Schematic

Diagram

A

select

line

must

remain

stableinthe

true

(low)

state

until

afteraSteporRead/Write

command

has

been

executed.

The drive

select

address

(1-4) is

determined

by

shorting

plugsonthe

circuit

board.

Select

lines

1

through4provide

a meansofdaisy

chaining

a maximumoffour

drivestoa controller.

Only

one

line

can be

true

(low)ata time. An

undefined

operation

might

result if

twoormore

units

are

assigned

the

same

addressorif

twoormore

select

lines

areinthe

true

(low)

state

simultaneously.

Circuit

Description

An

150-ohm

resistor

holds

the

outputofthe

appropriate

Select

line high (false)

until

the

line

is driven

low

(true). Then,

the

Select

signal is

gated

throughU1andUSto

derive

the

signal

DRSEL+.DRSEL+

is usedtogate

all

I/O

Port,

ensuring

that

only

one

drive's

dataispresentonthe

interfaceata time.

Writing

and

stepping

are also

gated

by

the

signal DRSEL+.This signal is

inverted

by

U13,

then

bufferedbyU15to

drive

the

Activity

L.E.D.,

whichislocatedonthe

front

panel.

Option

Z is

factory

installed.Itshould

be

installed

for

the

Activity

L.E.D.tooperate

with

Drive Select.

B.

MOTOR ON, Drive

Motor

Enable

3-2

TABLE

3-1 .

DRIVE INTERFACE

LINES

AND

CONNECTORS

Ground

1

3

5

7

9

11 13 15

17 19

21

23 25

27

29

31

33

35 37 39

41

43

45 47

49

Number

2

4

6

8

10

12

14

16

18

20

22 24

26

28

30

32

34

36

38 40

42

44

46

48

50

Signal

Write

Current

Switch

Motor

Off

Control

1

Motor

Off

Control

2

Motor

Off

Control

3

Two

Sided

(Strappable)

(Model

TM848-2

only)

Disk

Change

(Strappable)

Side

Select

(Model

TM848-2

only)

Activity

Indicator

(Strappable)

Head

Load

Line Index Ready Motor

Off

Control

4

Drive

Select1(Side

Select

Option,

TM848-2

only)

Drive

Select2(Side

Select

Option,

TM848-2

only)

Drive

Select3(Side

Select

Option,

TM848-2

only)

Drive

Select4(Side

Select

Option,

TM848-2

only)

Direction

Select

(Side

Select

Option,

TM848-2

only)

Step

Write

Data

Write

Gate

Track

00

Write

Protect

Read

Data

Alternate

I/O

Alternate

I/O

3-3

Functional

Description

The

TM848

has aD.C.

brushless

motor

that

can be

enabledinthree

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

On

lines.

3. By Drive Select, using

shorting

plug

M3.

The

MotorControllines,

MC1

through

MC4,

are

true

(low)

signals

that

turn

the

motor

off.

Shorting

plug

M2

must

be

installed

for

these

control

linestooperate.

WhenaMotor

Control

line is false (high),

the

drive

motor

acceleratestoits

operational

speed

in less

then

500

milliseconds. This

keeps

the

spindle

rotatingata

constant

speedof360

RPM.

When

the

Motor

Control

line is

true

(low)

the

motor

coaststoa stop.

When using

Head

Loadtoenable

the

drive motor,

M4

must

be installed. Allofthe

motors

are

enabled

when

the

Head

Load

line

goes

true

(low). M1

should

be installed if a

motor

turn

off

delay

is desired.

See

Section

1.19.21

foranadditional

descriptionofthis

circuit.

When a Drive

Select

lineistobeused

for

Motor

Enable,

M3

must

be installed. This

enables

the

drive

motor

when

the

Select

line

goes

low.

Circuit

Description

When

the

motorisenabledbyanyofthe

above, U35, Pin6,floats

high,

allowing

the

speed

control

U41

to

start

the

drive motor.

Two

Hall

Effect

transducersinthe

motor,

supply

the

necessary

feedback

signals

for

proper

speed

regulation.

When

U35-6

goes

high,

the

outputofU41, Pin6,turnson021,

whichinturn

applies

a varying

voltageto020

that

regulates

the

amountofcurrent

through

020,

and

the

motor

driver

transistors

01

through

04.

Transistors

01

through

04

are

turned

onbythe

gated

pulses

derivedfrom

the

conditioned

outputsofthe

Hall

Effect

transducers.The

conditioned

output

of

U38, Pin2, is

subsequently

conditionedbyGate

U36,

which

acts

asan

edge

trigger

and

pulse

doubler.

This signal is

fed

backtoU41, Pins 2

and3,which

resultsinclosed

loop

speed

control. The drive

motor's

rotational

speedisapproximately

2520

RPM,

when

adjusted,togiveaspindle

speedof360

RPM.

C.

DIR STEP,

Direction

and

Step

Lines

Functional

Description

When

the

drive is selected, a

true

(low)

pulse

withatime

duration

between

200

nanoseconds

and

2

millisecondsonthe

Step

line

initiates

the

track

access

motion. The

directionofmotionisdetermined

by

the

logic

stateofthe

Direction

line

whenaStep

pulse

is issued. The

motionistoward

the

center

of

the

driveifthe

Direction

line is in

the

true

(low)

state

whenaStep

pulse

is issued. The

direction

of

motionisaway

from

the

centerofthe

drive if

the

Direction

line is in

the

false (high)

state

whenaStep

pulse

is issued. To

ensure

proper

positioning,

the

Direction

line

shouldbestable

foraminimumof1

00

microseconds

before

the

trailing

edgeofthe

corresponding

Step

pulse. The

Direction

line

should

also remain

stable

until

100

microseconds

after

the

trailing

edgeofthe

Step

pulse. The

access

motionisinitiated

on

the

trailing

edgeofthe

Step

pulse.

When

the

carriageispositionedatTrack00and

the

stepper

motorisat

Phase0,

the

signalatPin42of

P13

goes

true

(low),

indicating

that

Track

00

has

been

reached.

When

steppinginor

out,

Test

Point

8 is a high

going

pulse

for

each

step

pulse

issued.

3-4

Circuit

Description

The

Direction

line

comes

in on Pin34of

the

interface

connector.

A high

signal

directs

the

step

logic

to

step

toward

Track

00. A

low

signal

directs

the

step

logictostep

towardahigher

numbered

track.

The

direction

line

sets

the

proper

phasetothe

exclusive

OR

gatesofU9.

TABLE 3-2

STEPPER LOGIC TRUTH TABLE

Step

Out

Toward

Track

00

Step

In Toward The

Upper

Tracks

Phase Phase

Pin No.

0

3 2 1

0

Pin No.

0

1

2

3 0

U21-9

0

1 1 0

0

U21-9

0

1 1

0

U21-B

1 0 0 1

1

U21-B

1

0 0

1

U21-5

0

0 1

1 0

U21-5

0

1

0

U21-6

1 1

0

1

U21-6

1

0

1 1

The

step

pulses

comeinat

Pin36of

the

interface

connector.

They

are

bufferedbyU22

and

gated

at

U14bythe

unit

select, and

the

Not

Write

signal.The

step

pulses

thengoto

theCinputsofthe

two

flip

flopsatU21.

The

directionofthe

step,

hence

the

selectionofthe

flip

floptobe

toggled,isdonebythe

two

exclusiveORgatesofU9.These

gates

are

controlledbythe

step

direction

line

andbythe

state

of

the

two

flip

flop

outputs.

The POR-

(Power

On

Reset) signal

resets

the

two

flip'

flopstoPhase 0

afteraPower

On.

The

outputofthe

twoflipflops

drives

the

stepper

motorthrough

the

driversofU39, U40,and U12.The

diodes, CR2-9, are

for

voltage

spike

elimination.

The

current

through

the

stepper

motor

coils

is

reversed

sequentially,

oneata time.

D.

WRf

GATE

Functional

Description

When

the

Write

Gate

signal is

true

(low),

the

write

electronics

are

prepared

for

writing

data

(read

electronics

disabled). This signal

turnsonthe

write

currentinthe

read/write

head. Data is

written

under

controlofthe

Write

Data

input

line.Itis

necessary

for

the

Write

Gate

interface

linetogo

low

before

the

first

Write

Data

pulse.

However,the

separation

between

the

leading

edgeofWrite

Gate

and

the

first

significant

Write

Data

pulse

should

notbeless

than

two

microseconds

and

not

greater

than

four

microseconds. The

same

restrictions

exist

for

the

relationship

between

the

last

Write

Data

pulse

and

the

terminationofthe

Write

Gate

signal. When

the

Write

Gate

line

goes

false (high),

the

trim erase will

stayonfor

550

microseconds

(see Trim Erase,

page

3-7).

When a

write-protected

diskette

is

installed

in

the

drive,

the

write

electronics

are disabled,

irrespectiveofthe

stateofthe

Write

Gate

line.

Check

the

listofoptions

(see

Section

1.19)

for

exceptions

and

further

discussionofwrite

protect

options.

Steppingisalso

disabledbya

true

(low)

Write

Gate.

Tandon

Corporation

recommends

that

the

controller

wait

one

millisecond

after

the

WRf

GATE

goes

high (false) be'fore

any

step

pulses

are

senttothe

drive.

Circuit

Description

A

low

(true) WRT GATE signal is

appliedtoPin

40ofthe

interface

connector

P13. This

signal

is

3-5

invertedand

gated

withWriteProtectand Drive

SelecttoenableU23, U30,and

013.

Transistors

013

and

012

are

write

current switches.

013

and

012

are on in parallel when

the

low Write

Current

interfaceis high (false). This results in awrite

currentof10

milliamps.When

the

low

WriteCurrentline

goes

low (true), transistor

012

turns

off, and

the

current decreasesto7 milliamps. R52 and

R51

determine

the

amount of

write

current suppliedtothe

head. The

network

CR1B, CR19, CR20,

RBO

and

RB1

is a power-loss

write

disable. If a sudden voltage loss occurs, transistor

014

turns

off,

disabling

the

write current.

E.

WRT DATA Functional Description When

the

driveisselected,

the

writedatalineprovides

the

bit-serialWrite Data pulses

that

control

the

switching of

the

write

current in

the

heads. The write electronics must be

conditioned

for writing by

the Write Gate line. Foreach high-to-Iowtransitionon

the

WRTDATA line,afluxchangeis produced at

the

headwritegap.

This causes a flux change

tobestored on

the

diskette

(see Figure 3-4).

N INTERNAL WRITE BUSY SIDE

SELECT

LOGIC

SIDE

SELECT

NWRITE

DATA

NWRITE

GATE

N WRITE PROTECT

UNIT

SELECT

o a

WRITE

DATA

TRIGGER

C

WRITE

CURRENT

SOURCE

ERASE

DELAY

LOGIC

IN

WRITE)

WRITE

DRIVER

1

WRITE

DRIVER

2

ERASE

CURRENT

SOURCE

READ!

WRITE

COILS

ERASE COIL

IN

INTERNAL

......

READ

DISABLE

~-------WRITE

BUSY)

Figure

3-4

Write Data Circuit Block Diagram

When a double-frequencytype encoding technique is used(in which data and

clock

form thecombined

Write Data signal),

it

is recommended

that

the

repetition of the high-to-Iow transitions, when writing

all zeros, be equal

to

the

nominal data rate ±0.1 percent. The repetition rate of the high-to-Iow

transitions, when writing all ones, should be equal

to

twice

the

nominal data rate

±O.1

percent. The

data transfer rate

for

a 1F pattern is

250,000

Bits Per Second (BPS). The data transfer rate

for

a 2F

pattern is

500,000

BPS.

3-6

Circuit

Description

Datais

senttothe

drivevia

interface

Pin 38. This signal is invertedbyU22, and is usedtoclock

the

D

flip

flop

U23. The

outputsofU23

are inverted subsequently,

and

usedtodrive

015

and

017,

which

direct

the

write

currenttothe

correct

winding.

F.

TRIM ERASE

Functional

Description

The

TM848

uses a

tunnel

erase

schemetoachieve

trim erase,

whichisusedtoerase a guard band

around

the

data

tracks, allowing

minor

track

offsets

and

minor

misalignment

without

data

errors

occurring.The erase

poles

are

staggered

.036

inch

behind

the

read/write

poles.At a mediarotational

speedof360

RPM,

the

tunnel

erase

method

requires

that

the

trim erase be

delayed

for

190

microseconds

afer

the

startofwriting

and

that

it be

continued

for

550

microseconds

after

the

end

of

writing

the

data. The

two

one

shotsinU30

provide

these

delay

time

intervals.

When

the

write

gate

goes

low, U30, Pin9,(A

input), is

triggered

and a hightolowtohigh

transition

of

190

us is generated. The

write

gate

is also appliedtoU30

Pin 1(Ainput).

When

the

write

data

is

appliedtothe

WRT DATA line,

U23

conditions

the

data

whichinturn

generates

the

signal WRT

TRAN+

(write

transition+).

This signal is

then

appliedtoU30

Pin2,(8

input)

which

is a positive

triggered

input.This

clock

will

retrigger

this

one

shot

continuously

until

the

last

transitionofthe

WRT

TRAN+

and WRT

GATE-

occurs.Atthis

time,

the

one

shot

stays on

foranadditional

550

us. These

outputs

(U30, Pins12and

13) are

gated

by U31

whichisthe

trime

erase gate. This

output

goes

low

whenever

both

inputs

are high,

causing

the

trim erasetobe

enabled

(see Figure 3-5).

G.

SIDE SELECT

Functional

Description

SIDE SELECTcan be

generated

three

ways.

See

the

option

listing,

Section

1.19,

for

this

information.

As

shipped

from

the

factory,

the

sideisselected

using

the

SIDE SELECT

interface

line.

When

the

Side

Select

signal is low,

Side

1 (the

upper

head)ofthe

drive is

selected

for

read/write

operations. When

this

signal is high,

Side

0 of

the

drive is

selected

(see Figure 3-6). The

Side

Select

signal must be

stable

duringanentire

readorwrite

operation. This signal is

best

implemented

in

synchronization

with

the

Drive

Select

line signal.

Circuit

Description

As

shipped

from

the

factory,

the

Side

Select

signal is received on Pin14of

edge

connector

P13. This

signal is received

by

U22, inverted,

then

inverted againbyU13.The

outputofU13, Pin 10,

generates

the

signal

called

Side

1-.

The

Side1-signal is

appliedtoU13, Pin9,and U24, Pin 13.The

outputofU13,Pin8,is

appliedtoU24,

1.

This

outputatPin 2ofU24isthe

oppositeofU24,

Pin12.

The

resistor

divider

network

sets

up

the

biasing

voltagestoturn

on and

turn

off

the

head

select

transistor,

018or019.

The head biasing

voltages

seen

across

the

collector

resistors will

be

5.2VD.C.

when

selecting

a head

for

a read

operation,

12V

D.C.

duringawrite

operation, andOVD.C.when

the

head is

not

selected. The

emitter

voltageson018

and

019

will alwaysbethe

oppositeofeach other,

causing

CTOorCT1

(center

tap

0,

center

tap1)tobeselected.

3-7

WRTGATE

WRT DATA

I

---J

~

I I

<1-

4usma<

550us

-i>1

I

_I

II.--

--[>

I I

<}-

190us

U

1<1-

_

__

Jr----------------I

U30, Pin 13 •

1.0,

------

Sec

B,

Q output

U30, Pin 12

Sec

A,

Q output

WRTTRAN +

U31, Pin3

Trim erase Source

Figure

3-5

Trim Erase Diagram

CTJ

51DE. \

POR.+

IN~

Wr.:.T

W::>Y-t:

~--4~cl)

I .

~\4

9~~

-----

~

~~e>-------!D~I~R'.:I+':

~4

+~v

-t-5V

+sv

ID

lif~.

5ii5E

14

5

-.

52.'0------

~14

".

0

5

\

150

11

+5V

. Figure 3-6

Side Select Schematic Diagram

3.4 OUTPUT

CONTROL

LINES

A.

INDEX/SECTOR

Functional

Description

The

Index

signal is provided

once

eash

revolution

(166.667

milliseconds

nominal)toindicate

the

beginningofa

tracktothe

controller.TheI

ndex

line remains in a

low

(true)

state

forthe

durationofthe

index

pulse.

The

durationofthe

Index

pulseisnominally

2.0 milliseconds.

Two

index

sensors

are

supplied

for

use

with

single-ordouble-sided

media.

The

leading

edgeofan

Index

pulse

is always used

for

timingtoensure

diskette

interchangeability

between

drives.

With a standard,

soft-sectored

diskette

installed,

the

signalatR33 (see

Figures

3-7

and

3-8) isa high

going

pulse,

nominally

2.0

milliseconds

in duration,

every

166.667

milliseconds.

Circuit

Description

Light

from

the

Index

L.E.D.

is usedtodrive

the

index

sensor,

whichisappliedtothe

inverting

input

of

U32. This signal is

conditioned

by

U32,

then

inverted

by

U33. It is

usedtodrive

U26. Then

the

Respective

index

pulses

are

gatedbyU20,

then

with

drive

selectbyU4togenerate

the

signal index.

U26

and

the

associated

support

integrated

circuitsU16

and

U20

are

configuredtoallow

only

the

Index

1 signaltobe

present

on

the

interface

whenatwo-hole

diskette

envelope

is used.

When a

double-sided

diskette

is installed,

the

signal IN1

FF+isgenerated

and

gatedbyU4toenable

the

output

TWO SIDED.

B.

Ready

Functional

Description

Ready is usedbythe

controllertoascertain

the

statusofthe

drive.This signal is

generated

when

the

drive

motor

is on,

the

diskette

installed,

and

the

drive is selected. The signal

takes

less than

700

millisecondstogo

true

(low) from a

motor

startbyDrive

SelectorHead

Load

(see

Section

1.19.21).

Circuit

Description

The

index

pulseisgatedbyU5,

which

in turn,

triggers

U17, a

220

millisecond

retriggerable

one

shot.

When

the

index-to-index

time

becomes

less than

220

milliseconds,

the

one

shot

becomes

continuously

enabled

and

generates

the

signal

SPIN-.

This signal is

gated

with

POR+,

Power

On

Reset,toenable

the

two-revolution

counters

U18. The

outputofU18, Pin8,enables

U6,

whose

outputisgated

with

Drive

Selecttogenerate

the

signal

ready.

Whenever

the

drive

motor

is disabled,

MTRON+

goes

low,

causing

this

sequence

to

be

repeated

when

the

motor

is restarted.

C.

Disk

Change

Functional

Description

The signal

DISK

CHANGEisusedtoindicate

the

host

controller

thatadisk

change

operation

has

been

made.

3-10

Circuit

Description

The

disk

change

flip-flop, U10,is resetbyOPEN-

whenever

the

lever

is in

the

open

position.

When

this

occurs, U

10-6

is high,

andatrue

disk

change

statusissenttothe

interfaceonPin12from U4-11.Flip-

flopU10issetonthe

trailing

edgeofdrive

select

causingU10-6togo

low

and

setting

the

disk

change

statustothe

false

state.

In

actual

use,

this

signal

can be

usedbythe

host

controllertodetermine

that

the

diskette

lever

has

been

opened

since

the

endofthe

select

operation.

r--'

I

~;f'--~ov

NOE')\.

\~~l{~9·

LED

"t.

1 1

7

(~

I i 'V

~..J.<iLJ~-~5V

''''OE'/..'Z.+"",I

~R~O-

LED

~

I~

I:

'V

1 I

d:

~~~V

"\

I 1

:

I:,

Figure

3-7

Index

Schematic

Diagram

U

166.667ms

- - -

---a.t

Figure

3-8

WaveformatTest

Point11or

12

Alternate

Test

Point, R33

Soft

Sectored

Diskette

Installed

D.

TRK

00

Functional

Description

When

the

driveis selected,

the

Track00interface

signal

indicatestothe

controller

that

the

read/write

head is

positionedatTrack

00. The

Track00signal

remains

true

(low)

until

the

head is moved

away

from

Track

00. The

Track

00

sensorisactivated

internally

between

Tracks 2

and

3.

Interface

Pin42(see

Figure

3-9) is

true

(low)

when

the

carriageispositionedatTrack00and

the

step

motorisat

Phase

O.

3-11

P2.

r-,

Rt14

TR~CK

~~+5V

L~.O

~~

I I

\l

I I

TI1J).C~

C)>-i-':Z=-----.+5V

(1)

I I

~E.W50R..

I

II

I>i-'---..---+----~

L_.J

R1'5

I

Cc..c..

22K.Z.--lOOlpf

V V

pD

I I

221<.

RP3

RP2. 4701<.

U~I\'i

+SV

\PIO

.

I R.P4

2.

4:7K..

Figure

3-9

Track

00

Schematic

Diagram

Circuit

Description

When

the

read/write

carriageisrestoredtoTrack

00, a

tabonthe

carriage

blocks

light

from

the

Track

00

L.

E.

D.,

turning

off

the

Track00sensor

transistor.

This

enables

the

inverting

inputofU32, a

quad

comparator

causing

U32,

Pin 13,togo

high.

This

signalisgated

with

Phase0of

the

step

circuit

and

with

drive

selecttogenerate

the

signal

TRK

00.

The

signalatTest

Point10shouldgohigh

between

Tracks2and

3, as

the

carriageisbeing

moved

toward

TRK

00.

E.

WRITE PROTECT

Functional

Description

When

the

driveisselected

and

the

disketteiswrite

protected,

the

WRITE PROTECT

line's

true

(low).

The

write

electronics

are

internally

disabled

when

the

disketteiswrite

protected

(see

Option

Listing

for

exceptions).

When

the

signalonthe

WRITE PROTECT

lineisfalse

(high),

the

write

electronics

are

enabled

and

the

write

operation

canbeperformed.Itis

recommended

that

the

controller

not

issueaWrite

command

when

the

Write

Protect

signalistrue

(low).

It is

recommended

that

the

Write

Data

linebeinactive

whenever

Write

Gateisfalse

(high).

Circuit

Description

Whenawrite

protected

disketteisinstalled,

light

from

the

Write

Protect

L.

E.

D.isdetectedbythe

Write

Protected

sensor

transistor.

The

outputofthe

sensorishigh

andisconditioned

by

U32.

The

outputatPin

14islow

generating

the

signal

WR PROT-.

This

signalisused

internally

with

the

read/write

circuitry.

The

signal

WR PROT- is

invertedbyU33,

and

gated

with

DR

SEL+to

generate

the

Write

Protect

signal.

F.

READ DATA

Functional

Description

The

Read

Data

interface

line

transmits

the

read

datatothe

controller

when

the

driveisselected.

It

providesapulse

for

each

flux

transition

recordedonthe

media.

The

Read

Data

output

line

goes

true

(low)

foradurationof200

nanoseconds

for

each

flux

change

recorded.

The

leading

edgeofthe

low

going,

read

data

output

pulse

represents

the

true

positionsofthe

flux

transitions

on

the

diskette

surface.

3-12

tzt;

p~

~

WR\TE

_;

I I

150

PROTECT

,;v-

I I

L.E.D.

~

WRITE:

"'~)

:2.

+5V

PROTECT

: I

SENSOR

>;;-:-,

--

........

--.----

L_J

RPZ

7

22~

8

TP7

+5V

5

RP4

4.71(,

Figure

3-10

Write

Protect

Schematic

Diagram

Test

Points2and

3 (see

Figure

3-11)

are

providedtoobserve

the

differential

outputofthe

first

stage

of

Read

signal

preamplification.

Test

Points4and

5 are

providedtoobserve

the

differential

output

of

the

second

stage

amplifier

and

differentiated

Read signal.

Test

Point

9 is

the

outputofthesingle

shot

used in

the

Read section,

nominally

200

nanoseconds

for

each

flux

transition

detected.

Test

Point

1

is signal ground.

Circuit

Description

The read signal

comes

from

the

selected

head on

the

drive.Itis

gatedtothe

preamplifier

U7bythe

-Write

signaltoU25,

which

forward

biases

diodes

CR14

and

CR15. Then,

the

Read signal passes

throughalinear

bandpass

filter. The Read signal is

then

inputtoU2,

the

differentiator.

The

outputofU2

goes

through

theD.C.

blocking

capacitorstothe

crossover

detector,

U8,

which

digitizes

the

signal. This

converts

the

signal

into

standard

TIL

level I

ntegrated

circuits

U9, U11,

and

U10

compriseacomparator

circuit.

Any

pulses

that

occur

outsideofthe

normal

duty

cycleofU11are

eliminated. U9 is an

edge

detector.

U11

acts

as a

one

shot,

withatimeoutofapproximately

860

nanoseconds.U10 is

the

actual

comparator.

The Read signal is

presentedtoU9. Then it

goestoU11,

where

the

pulses

are

shapedto200

nanoseconds.This

outputisgatedatU29

with

the

Unit

Select

signaltoproduceadigital

outputatPin

46ofthe

interface

connector

(see

Figure

3-12).

Note

U11,

the

final

one

shot, is

disabled

when

the

drive is

writing

data

onto

the

diskette.

G.

Two

Sided

Functional

Description

This

output

enables

the

controllertodetermine

if a

diskette

is installed,

which

utilizes

the

Index

2

index

hole.This maybe usedtoindicatetothe

host

controller

thatatwo-sided

diskette

is in

the

drive.

3-13

T POINT 3

TEST POINT 2

....

T

UPPER

...

HEAD

...

......

....

---..

I

READ AND HEAD

SIGNAL

SWITCHING

AMPLIFIER

~TES

...

CIRCUITS

....

LOWER

~

......

HEAD

...

TEST POINT 4

,

~

l+

.....

CROSSOVER

....

TIME DOMAIN

DIFFERENTIATOR

,

....

DETECTOR

r

FILTER

.....

TEST POINT 5

~

....

DIGITIZER

.....

DATA OUTPUT

NT

WAT BUSY

-f

,.4~

UNIT SELECT _

Figure

3-11

Read

Circuit

Block

Diagram

Circuit

Description

When a

two-sided

diskette

is installed,

the

signal IN1

FF+isgenerated

and

gatedbyU4toenable

the

low-going

output

Two

Sided. The IN1 FF signal also

goestothe

ready

circuitryatU6-5todisable

Ready in

the

event

that

the

upper

head (Head 1) is

selected

whenasingle-sided

(Head0)diskette

is

installed (see

Option

RM

for

further

discussion).

3-14

Figure

3-1~Diagram

t

Schematic

Read Da a

SECTION

IV

TROUBLESHOOTING

GUIDE

4.

INTRODUCTION

This

sectionispresentedinthe

formofa table.

Each

section

contains

four

major

parts:

1.

The

section

number.

2. A

statementofthe

presenting

condition.

3. A

listofthe

possible

causesofthe

condition.

4.

The

recommended

actiontobe

taken.

4-1

SECTION

4.1

CONDITION

NOT READY

AND/OR

NO INDEX

POSSIBLE CAUSE

Diskette

not

inserted.

Diskette

not

clamped.

Unit

not

selected.

Drive

motor

not

turning

I

ndex

sensor

not

connected.

Index

sensor

defective.

RECOMMENDED ACTION

Insert

diskette.

Turn

knob

lock

lever

clockwisesothat

it

is

perpendicular

to

the

diskette

insertion

slot.

Verify

unit

select

and

jumper

configuration.

Verify

interface

drive

motor

on.

Check

Connector

P6.

Verify drive

belt

installed

Replace

circuit

board.

Replace Drive

Motor

Assembly.

Check

P1.

Replace

index

sensor.

4.2

WILL

NOT SEEK

OR RESTORE

Interface

not

enabled. Verify

interface

direction,

step, and

select

signals.

Step

motor

disconnected.

Check

Connectors

P4 and P5.

Defective

step

logic.

Defective

stepper

motor.

Wrong

option

selected.

4-2

Replace

circuit

board.

Replace

Stepper

Motor

Assembly.

Check

options

OS

and HL

for

the

particular

application.

SECTION

CONDITION

POSSIBLE CAUSE

RECOMMENDED

ACTION

-----

4.3

WILL

NOT WRITE

I

nterface

not

enabled.

Verify

write

enable, select,

and

write

data

interface

lines.

Headsorwrite

protect

switch

not

connected.

Check

Connectors

P3, P8,

and

P9.

Write

protect

switch

misadjusted.

Check

write

protect

switch

operation.

Defective

write

logic.

Replace

circuit

board.

Defective

heads.

Replace

Head

Carriage

Assembly.

Misadjusted

platen

Adjust

platen

load arm.

4.4

WILL

NOT READ

Interface

incorrect.

Verify

selectistrue

and

write

enable

is false.

Alignment

off.

Verify

C.E.lobes,

index

burst,

and

Track00sensor

adjustment.

Defective

read

Replace

circuit

electronics.

board.

Defective

heads.

Replace

Head

Carriage

Assembly.

Platen load arm misadjusted.

Adjust

platen

load arm.

4.5

ACTIVITY

L.E.D. INOPERATIVE

I

nterface

not

enabled.

4-3

Verify

interface

select

and

jumper

configuration.

SECTION

CONDITION

POSSIBLE CAUSE

RECOMMENDED

ACTION

4.5 ACTIVITY L.E.D. INOPERATIVE

Activity

L.E.D.

Check

P11

not

connected.

Activity

L.E.D. Replace

Activity

defective.

L.E.D.

Assembly.

Activity

L.E.D. Replace

circuit

driver

defective.

board.

4.6

NO TRACK

00 SENSOR INDICATION

Defective

seek.

See

Section

4.2

4.7

Track

00

sensor

not connected. Defective

logic.

Defective

Track

00

sensor.

DRIVE MOTOR WILL

NOT START WHEN DOOR LATCHED.

Defective

microswitch.

M

icroswitch

not

connected. Misadjusted

switch

bracket.

4-4

Check

P2.

Replace

circuit

board.

Replace TrackOO Sensor

Assembly.

Replace switch.

Check

P14.

Realign.

SECTION

V

REPLACEMENT

PROCEDURES

5

INTRODUCTION

This

section

contains

the

replacement

procedures

for

the

TM848

familyofdisk

drives'

parts

and

assemblies:

'1.

0 rive

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.

Track00Sensor

Assembly

1

"I.

Write

Protect

Sensor

Assembly

12.

Door

Switch

Assembly

1

~3.

Index

Sensor

Assembly

14.

Diskette

Ejector

Assembly

1

t5.

Load

Resistor

Assembly

16.

Stepper

Band

17.

Stepper

Motor

Assembly

18.

Head

Carriage

Assembly

5.1

DRIVE

BELT

5.1.1 Removal A.

Turn

the

drive

oversothat

the

spindleisfacing

upward

(see

Figure

5-1).

5-1

DRIVE BELT

o

SMALL FLANGED SPINDLE PULLEY

o

c==>

J

o

LARGE

SPINDLE

PULLEY

Figure

5-1

Drive

Belt

and

Spindle

B.

Grasp

the

drive belt,

and

remove it from

the

pulleys.

5.1.2

Installation

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

beltonthe

large

spindle

pulley.

5.1.3

Checks

A.

After

turning

the

drive

motor

on,

check

that

the

drive

belt

does

not

sliporfall off

the

large

pulley.

B.

Check

the

spindle

speed

(see

Section

II).

5.2 DRIVE MOTOR

5.2.1 Removal

A.

Remove

the

drive

belt

(see

Section

5.1).

B.

After

turning

the

driveover,

cut

the

tie

wraps

that

hold

the

drive

motor's

wires

(see Figure5-2).

C.

Unplug

P6 from

the

circuit

board.

D.

Remove

the

three

mounting

screws

that

attached

the

drive

motor

tothe

chassis.

E.

Lift

out

the

drive motor.

5.2.2

Installation

A.

Set

the

drive

motoronthe

chassis,

aligning

the

three

mounting

holes.

B.

Reinstall and

tighten

the

three

mounting

screws.

5-2

DRIVE MOTOR

DRIVE MOTOR WIRES

P6

Figure 5-2

Drive

Motor

and

Related Parts

C.

Carefully

rebundle

the

wires,

including

the

drive

motor

wire,

and

cable

harness

them

(see

Figure

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

Checks

A.

Checktoensure

that

the

drive

motor

works.

B.

Check

the

spindle

speed

(see

Section

II).

5.3 CIRCUIT BOARD

5.3.1 Removal A.

Remove all

the

connectors

from

the

circuit

board.

B.

Remove

the

two

side

mounting

screws

that

connect

the

two

regulator

heat

sinkstothe

drive's

chassis (see

Figure

5-3).

C.

Remove

the

screw

and

the

retaining

clip

that

attach

the

circuit

boardtothe

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

slot

provided (see

Figure

5-3).

5.3.2

Installation

A.

Install

the

power

connector

by

rethreading

the

power

wires

and

pushinginthe

power

connector

from

the

backofthe

drive.

5-3

RETAINING CLIP'

---=--_~

Figure

5-3

Circuit

Board

Mounting

Screws

B.

Remount

the

circuit board using

the

two

screwstothe

two

heat

sinks

and

the

screw

and

nylon

clip

that

attach

the

circuit

boardtothe

drive's chassis.

C.

Plug in all

connectors,

ensuring

that

each

oneisseated

correctly

in its

proper

location.

5.3.3

Checks

A.

Verify

the

select

and

options

configuration.

B.

Applying power,

check

the

operationofthe

drive.

5.4

CONE

ASSEMBLY

5.4.1 Removal A.

Remove

the

screw

that

attaches

the

cone

brackettothe

cone

alignment

arm (see Figure 5-4).

B.

Unlatch

the

diskette

lever.

C.

Swing

the

Cone

Assemblyup90

degreessothatitpoints

toward

the

sideofthe

drive.

D.

Carefully

remove

the

E-Ring, flat washer,

and

washer

that

holdsonthe

cone

shaft.

E.

Gently

lift

out

the

Cone

Assembly.

5.4.2

Installation

A.

Gently

insert

the

Cone

Assembly.

B.

Carefully

insert

the

E-Ring, flat washer, and wave

washer

that

holdsonthe

cone

shaft

(see

Figure

5-5).

C.

Swing

the

Cone

Assembly

down90degreessothatitpoints

toward

the

bottomofthe

unit.

5-4

CONE BRACKET

SCREW

CONE

ALIGNMENT

ARM

CONE ASSY

Figure

5-4

Cone

Assembly

Key

Parts

D.

Latch

the

diskette

lever.

! E-RING &WASHER

WAVE WASHER

E.

I

nsert

the

screw

that

attaches

the

cone

brackettothe

cone

alignment

arm(see

Figure

5-5).

t

E-RING

~

~-~-------

~i=c::::::l""""------

FLAT WASHER

~i~""""

WAVE WASHER

I:~f?:t"tj:@~

?]f!M,j~A~tfrJ!

.....

o1(f------

CONE

BRACKET

FLAT WASHER (2)

Figure

5-5

Cone

Assembly

Parts

5.4.3

Checks

A.

Ensure

that

the

Cone

Assembly

turns

freely.

B.

If not, reverify

that

the

Cone

Assembly

has

been

installed correctly.

C.Insertadiskette. D.

Ensure

that

the

disketteisclamped

properlybythe

cone.

5-5

5.5 DISKETTE LEVER

5.5.1 Removal A.

Pry

off

the

cover

that

hides

the

diskette

lever's retaining

screw

(see

Figure

5-6).

MOUNTING

SCREW

~"

COVER

DISKETTE LEVER

Figure

5-6

Diskette

Lever

Key

Parts

B.

Remove

the

diskette

lever's

retaining

screw.

C.

Carefully

remove

the

diskette

lever.

5.5.2

Installation

A.

Put

the

diskette

leveronthe

shaft.

B.

Put a

dropofLocktite

Number

234

on

the

threadsofthe

diskette

lever's screw.

C.

Install

and

tighten

the

diskette

lever's screw.

D.

Put

the

cover

backonthe

diskette

lever.

5.5.3

Checks

A.

Ensure

that

the

diskette

leverisperpendiculartothe

drive

when

the

diskette

isclamped.

See

Figure 5-7

for

the

adjustment.

.B.Ensure

that

the

diskette

lever

is paralleltothe

drive

when

the

diskette

is unclampled.

See

Figure 5-7

for

the

adjustment. -

5.6 BRIDGE

ASSEMBLY

5.6.1 Removal 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

Assemblytothe

chassis

(see)

Figur

5-8).

5-6

BEZEL

SCREWS 2 BOTH SIDES

Figure

5-7

Diskette

Lever

Adjustment

BRIDGE

MOUNTING

SCREWS

2 BOTH SIDES

I

•

I

~

Figure

5-8

Bridge

Assembly

Key

Parts

BEZEL

~

DISKETTE LEVER

'---

BEZEL

MOUNTNG SCREWS, 2

@

D.

Carefully

pull

out

the

two

indexL.E.

D.'s in

the

Bridge

Assembly.

E.

Carefully

lift

out

the

Bridge

Assembly

toward

the

backofthe

drive. The

shaft

must

clear

the

bezel.

5.6.2

Installation

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

Assemblytothe

chassis.

C.

Install

the

two

index

L.E.D.'s

into

the

Brid.ge 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

.....--------1

MOUNTING SCREWS (2 EA SIDE)

FigureS-9

~

Bridge

Assembly

Additional

Key

Parts

5.7

BEZEL

5.7.1 Removal A.

Remove

the

diskette

lever

(see

Section

5.5).

SHAFT

MOUNTING

SCREWS

(2EASIDE)

B.

Remove

the

four

bezel

mounting

screws,

two

on

each

side,

that

attach

the

bezeltothe

chassis

(see

Figure

5-10).

~

DISKETTE LEVER

BEZEL MOUNTING SCREWS, 2

Figure

5-10

Bezel

and

C.

Lift

off

the

bezel,

being

careful

that

the

Activity

L.

E.

D.

comes

outofits

mounting

with

no

binding.

5-8

5.7.2

Installation

A.

Put

the

bezelonthe

drive,

ensuring

that

the

Activity

L.

E.

D.

goes

into

its

holder.

B.

Install

the

four

bezel

mounting

screws

that

attach

the

bezeltothe

chassis.

5.7.3

Checks

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.

5.8 ACTIVITY

L.

E.

D.

5.8.1 Removal A.

Remove

the

bezel

(see

Section

5.7.1).

ACTIVITY

LED.

(INSIDE)

ACTIVITY LIGHT WIRES

BRACKET

1 NEAR SIDE

TIE BRACKETS

2 FAR SIDE

J 0

o~

o 0

B.

Remove

the

brackets

that

hold

the

bundleofwires

goingtoP11 from

the

chassis

(see

Figure

5-11

).

Figure

5-11

Activity

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.

wirestothe

chassis

with

brackets

(see

Figure

5-11).

D.

Plug P11

into

the

circuit

board.

5.8.3

Checks

A.

Ensure

that

the

Activity

L.

E.

D.

does

not

interfere

with

the

drive

mechanisms.

B.

Ensure

that

the

Activity

L.

E.

D.

goesonwhen

required.

5-9

5.9 LOAD

ARM

ASSEMBLY

5.9.1 Removal A.

Remove

the

circuit

board

(see

Section

5.3.1).

B.

Remove

the

mounting

screw

and

washer

that

are

usedtoattach

the

Load

Arm

Assembly

to

the

chassis

(see

Figure

5-12).

LOAD ARM

....

REAR

MOUNTING

SCREW, WASHER, AND SPRING

Figure

5-12

Load

Arm

Assembly

Key

Parts

C.

Carefully

slide

out

the

Load

Arm

Assembly

toward

the

rearofthe

chassis.

5.9.2

Installation

A.

Slide

the

Load

Arm

Assembly

into

position

from

the

rearofthe

chassis,

ensuring

that

the

load

springissitting

under

the

front of

the

mounting

screw.

B.

Install

and

tighten

the

mounting

screw

that

attaches

the

Load

Arm

Assemblytothe

chassis,

ensuring

that

the

washerisunder

the

screw

and

that

the

head

lift

armisover

the

Load

Arm

Assembly.

C.

Install

the

circuit

board

(see

Section

5.3.2).

5.9.3

Checks

A.

Insertadisketteinthe

drive.

B.

Ensure

that

the

headisloaded

when

the

diskette

leverisactivated

and

that adequate

clearanceisattained

for

diskette

insertion

and

ejection

(see

Section

II).

5.10

TRACK

00

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

o

TRACK

00 SENSOR ASSEMBLY

BFIACKET

-++-t---:;;~~~

Figure

5-13

Track00Sensor

Assembly

Key

Parts

C.

Remove

the

P2

wires

from

the

bracket

attachedtothe

chassis.

D.

Remove

the

two

mounting

screws

that

hold

down

the

Track

00

Sensor

Assembly.

E.

Lift

off

the

Track00Sensor

Assembly.

5.10.2

Installation

A.

Using

the

two

original

mounting

screws, install

the

Track00Sensor

Assembly.

B.

Loop

the

P2

wires

from

the

Track00Sensor

Assembly

through

the

bracket

attachedtothe

chassis.

C.

Using

tie

wraps,

cable

harness

the

P2

wires

and

the

other

wires

together.

D.

Plug P2

into

the

circuit

board.

5.10.3

Checks

A.

Adjust

the

Track00sensor

(see

Section

II).

5.11

5.11.1

WRITE PROTECT

SENSOR

ASSEMBLY

Removal

A.

Remove P3 from

the

circuit

board.

B.

Remove

the

two

mounting

screws

that

attach

the

Write

Protect

Sensor

Assemblytothe

chassis

(see

Figure

5-14).

C.

Cut

the

tie

wraps

that

hold

the

wirestothe

cable

harness,

and

lift

out

the

Write

Protect

Sensor

Assembly.

5-11

MOUNTING

SCREWS (2) .

P3

WRITE PROTECT

SENSOR

ASSY.

Figure

5-14

Write

Protect

Sensor

Assembly

Key Parts

5.11.2

Installation

A.

Using

the

two

original

mounting

screws,

attach

the

Write

Protect

Sensor

Assemblytothe

chassis.

B.

Plug P3

into

the

circuit

board.

C.

Tie

wrap

the

Write

Protect

wirestothe

cable

harness.

5.11.3

Checks

A.

Verify

operationofthe

Write

Protect

Sensor

Assembly.

5.12

5.12.1

DOOR SWITCH

ASSEMBLY

Removal

A.

Remove

P14

from

the

circuit

board.

B.

Remove

the

mounting

screw

from

the

door

switch

bracket

(see Figure 5-15).

C.

Cut

the

tie

wraps

leadingtoP14.

D.

Lift

out

the

Door

Switch

Assembly.

5.12.2

Installation

A.

Mount

the

Door

Switch

Assemblytothe

bridge, using

the

original

mounting

screw.

B.

Plug

P14

into

the

circuit

board.

5.12.3

Checks

A.

Ensure

that

the

door

switch

operates

properly.

5-12

5.13 INDEX

SENSOR

ASSEMBLY

MOUNTING

SCREW

P14

DOOR SWITCH

ASSEMBLY

Figure

5-15

Door

Switch

Assembly

Key

Parts

5.13.1

Removal

A.

Remove

the

circuit

board

(see

Section

5.3.1).

B.

Gently

remove

the

two

index

L.E.D.

's from

the

Bridge

Assembly

(see

Figure

5-16).

P1

UPPER INDEX

SENSORS

TIE WRAPS

Figure

5-16

Index

Sensor

Assembly

Key

Parts,

Top

View

c.

Turn

the

drive

over

and remove

the

mounting

screw

from

the

Index

Sensor

Assembly

(see

Figure

5-17).

D.

Remove

the

two

brackets

that

attach

theIndex

Sensor

Assembly's

wirestothe

chassis

(see

Figure

5-16).

5-13

E.

Cut

the

tie

wraps

along

the

cable

harness

(see

Figure

5-16).

F.

Lift

out

theIndex

Sensor

Assembly

(P1).

TIE BRACKETS, 2 FAR SIDE

TIE BRACKET. 1 NEAR SIDE

MOUNTING

SCREW

o

J

o

0

Figure

5-17

Index

Sensor

Assembly

Key

Parts,

Bottom

View

5.13.2

Installation

A.

Put

the

Index

Sensor

Assembly

into

the

drive.

B.

Loop

the

wirestothe

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.tothe

drive's

chassis.

E.

Cable

harness

the

bundleofwires,

including

theIndex

Sensor

Assembly's

wires.

F.

Reinstall

the

circuit

board

(see

Section

5.3.2).

5.13.3

Checks

A.

Check

the

index-to-data

adjustment

(see

Section

II).

5.14

DISKETTE EJECTOR

ASSEMBLY

5.14.1 Removal A.

Remove

the

circuit

board

(see

Section

5.3.1).

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

(see

Figure

5-7).

5-14

EJECTOR SPRING

TRIGGER

ASSEMBLY

Figure

5-18

Diskette

Ejector

Assembly

Key

Parts

D.

Lift

up

the

Bridge

Assembly

approximately

two

inches,

taking

care

nottopull

the

L.

E.

D.'s

from

their

sockets.

E.

Release

the

spring

attachedtothe

rearofthe

ejector.

F.

Remove

the

ejector.

5.14.2

Installation

A.Insert

the

ejector.

B.

Engage

the

spring

attachedtothe

rearofthe

ejector.

C.Insert

the

Bridge

Assembly

approximately

two

inches,

taking

caretoput

the

L.

E.

D.'sin

their

respective

sockets.

D.

Reinstall

the

original

four

screws

that

hold

the

Bridge

Assembly.

E.

Push on

the

lever.

Reinstall

the

retaining

screw.

Insert

the

small

pluginthe

door

lever.

F.

Reinstall

the

circuit

board

(see

Section

5.3.1).

5.14.3

Checks

A.Insertawork

diskette

into

the

drive.

B.

Ensure

that

the

diskette

staysinpriortobeing

closed.

C.

Close

and

open

the

diskette

lever.

D.

The

diskette

should

eject.

E.

If

not,

see

Section

5.4.

5.15 LOAD RESISTOR

ASSEMBLY

5-15

5.15.1 Removal A.

Remove

P5

from

the

circuit

board.

B.

Remove

the

circuit

board

(see

Section

5.3.1).

C.

Remove

the

two

mounting

screws

that

attach

the

Load

Resistor

Assemblytothe

chassis.

D.

Unsolder

the

wirestothe

load

resistors

(see

Figure

5-19).

E.

Markoridentify

these

wiressothat

they

can

be

put

backinthe

same

location.

SOLDER JOINT, 4 PLACES

LOAD RESISTOR ASSEMBLY·

Figure

5-19

Load

Resistor

Assembly

and

Key

Parts

5.15.2

Installation

A.

Solder

the

wires

backinthe

same

placeatwhich

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).

D.

Plug P5

into

the

circuit

board.

5.15.3

Checks

A.

Enable

the

drive

through

the

interface

logic.

B.

Step

the

drivetoTrack

00.

C.

Step

the

drivetoTrack

76.

D.

Do

the

C.E.alignment

verification

procedure

(see

Section

II).

5-16

5.16

5.16.1

STEPPER

BAND

Removal

It

is

suggested

that

the

drivebereturnedtoan

authorized

Tandon

repair

center

when

removing

the

stepper

band.

A.

Remove

the

circuit

board

(see

Section

5.3.1).

B.

Lift

off

the

stepper

band

from

the

spring

tensioner

(see

Figure

5-20).

SCREW, ATTACHES BANDTOCARRIAGE

ASSEMBLY

SPRING

TENSIONER

Figure

5-20

Stepper

Band

Key

Parts

C.

Remove

the

screw

that

attaches

the

frontofthe

stepper

bandtothe

Head

Carriage

Assembly.

D.

Remove

the

mounting

screw

that

attaches

the

stepper

bandtothe

stepper

pulley.

E.

Lift

out

the

stepper

band.

5.16.2

Installation

A.

Screw

the

frontofthe

stepper

band'into

the

Head

Carriage

Assembly

(see

Figure

5-21).

B.

Loop

the

stepper

band

around

the

stepper

pulley.

C.

Attach

the

rearofthe

bandtothe

spring

tensioner.

D.

Attach

the

stepper

bandtothe

stepper

pulley

loosely

with

the

mounting

screw.

E.

Move

the

Head

Carriage

Assembly

back

and

fourthatleast

five times.

F.

Visually

inspect

the

stepper

bandtoensure

that

it is

centered

on

the

stepper

pulley.

G.

Tighten

the

mounting

screw

that

attaches

the

stepper

pulleytothe

stepper

band.

H.

Install

the

circuit

board

(see

Section

5.3.2).

5.16.3

Checks

A.

Check

the

C.E.alignment

(see

Section

II).

5-17

STEPPER MOTOR

ASSEMBLY

o

MOUNTING

SCREWS, 3 PLACES

5.17

5.17.1

Figure

5-21

Stepper

Band

Additional

Key

Parts

STEPPER

MOTOR

ASSEMBLY

Removal

It is

suggested

that

the

drivebereturnedtoan

authorized

Tandon

repair

center

when

removing

the

Stepper

Motor

Assembly.

A.

Remove

the

circuit

board

(see

Section

5.3.1).

B.

Remove

the

stepper

band

(see

Section

5.16.1).

C.

Remove

the

three

mounting

screws

that

attach

the

Stepper

Motor

Assemblytothe

chassis

(see

Figure

5-22).

D.

Remove

plug

connectors

P4

and

P5

from

the

circuit

board.

E.

Cut

the

tie

wraps

that

connect

the

stepper

motor

wirestothe

load resistors.

F.

Lift

out

the

Stepper

Motor

Assembly.

Note

Be

careful

nottodamage

the

stepper

band.

5.17.2

Installation

A.

Place

the

Stepper

Motor

Assembly

into

the

drive's

chassis.

B.

Using

the

original

three

mounting

screws,

attach

the

Stepper

Motor

Assemblytothe

chassis.

5-18

STEPPER MOTOR

ASSEMBLY

o

MOUNTING

SCREWS, 3 PLACES

Figure

5-22

Stepper

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

Checks

A.

Align

the

C.E.lobesonthe

drive

(see

Section

II).

5.18

5.18.1

HEAD CARRIAGE

ASSEMBLY

Removal

It is

suogested

that

the

drivebereturnedtoan

authorized

Tandon

repair

center

when

removing

the

Head

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

cablestothe

chassis.

D.

Remove

the

clip

that

holds

the

head

cablestothe

head

cable

flexure

bracket.

E.

Remove

the

four

mounting

screws

that

attach

the

carriage

shafttothe

chassis

(see

Figure

5-

23).

5-19

MOUNTING

SCREWS

4 PLACES

Figure

5-23

Head

Carriage

Removal

F.

Lift

out

the

Head

Carriage

Assembly.

5.18.2

Installation

A.Install

the

carriage

shaftinthe

carriage.

B.

Using

the

four

original

mounting

screws,

attach

the

carriage

shafttothe

chassis.

C.Install

the

Stepper

Motor

Assembly

(see

Section

5.17.2).

Note

Take

care

nottodamage

the

Arm

Spring

Assembly.

D.

Plug

connectors

P8

and

pg

into

the

circuit

board.

E.

Cable

harness

the

Head

Carriage

Assembly's

wirestothe

main

wire

bundle.

5.18.3

Checks

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

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APPENDIX

II

RECOMMENDED

SPARE

PARTS

LIST

PARTS

AND

SUBASSEMBLIES

Part

Drive

Belt

Drive

Motor

Circuit

Board

Cone

Assembly

Diskette

Lever

Bridge

Assembly

Bezel

Activity

L.

E.

D.

(Front

Panel)

Load

Arm

Assembly

Track00Sensor

Assembly

Write

Protect

Sensor

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Door

Open

Switch

Assembly

Index

Sensor

Assembly

Diskette

Ejector

Assembly

Head

Carriage

Assembly:

Single-Sided

Recording

Double-Sided

Recording

Stepper

Motor

(Mounting)

Assembly

Stepper

Band

Load

(Power)

Resistors

Diskette

Lever

Lock

Ejector

Spring

Load

Arm

Spring

Note

All

components

are

standard

commercial

parts

purchasedtooriginal

equipment

manufacturer's

specifications.

Part

Number

210062-000 210061-000 210094-000 210085-000 210084-000 210086-000 210011-000 210081-000 210089-000 210080-000 210079-000 210083-000 210075-000

210124-000

210065-001

-

210065-002_ 210090-000 210112-000 210076-000 210082-000 210036-000 210122-000

OEM

OPERATING

AND

SERVICE

MANUAL,

TM848-1

AND

TM848-2

THINLINE™DISK

DRIVES,

48

TPI,

TANDON

179031-001

ALIGNMENT

DISKETTE

Recommended:

Dysan

8006~0,

Model

Number

360/2A

"

-1

1.7~031-001

(1082)

Tandon TM848-2 Operating And Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual