Tandon TM848-1 Service manual

OEM
OPERATING AND SERVICE MANUAL
TM848-1 AND TM848-2 DISK DRIVES
48 TRACKS PER INCH
'anCion
CORPORATION
20320 PRAI RI ESTREET
CHATSWORTH, CA 91311
TELEPHONE NO.: [phone]
TWX NO.: 910 494 1721
TEL.EX NO.: 194794
COPYRIGHT 1982 TANDON CORPORATION

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

Sectoon
Number
SECTION I
TABLE OF CONTENTS
Title of Section
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
Purpose Of The Drive 1-1
Physical Description of The Drive 1-1
Functional Description of The 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
Operation of The Drive 1-7
Organization of The Drive 1-7
Components of The 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 Pin Assignments, P13 1-12
Power Connector Pin 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
Title of Section
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 Description of The 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
4.1
4.3
4.4
4.5
4.6
4.7
Introduction " " ., " .. 4-1
Not Ready and/or No Index , .. 4-2
Will
Not Seek or Restore 4-2
Will
Not Write 4-3
Will
Not Read 4-3
Activity L.E.D. Inoperative 4-3
No Track 00 Sensor Indication 4-4
Drive Motor Will Not Start When Door Latched 4-4
SECTION VREPLACEMENT 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
Title of Section
Page
Number
5,8
5,9
5,10
5,'11
5,12
5,13
5,'14
5,'15
5,'16
5,'17
5.'18
Activity L, E, D",. , " , " , ., ", """ , . , ., , . " ., ., ", .. , . , , , . , ., " ", ., ,5-9
Load Arm Assembly, ., .. , , , , ., , , . , ,, , , , ,. , ... , , , , ., . , , . , , , , , ., , . , . , .. , . , . 5-10
Track 00 Sensor 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 IPRINTED CIRCUIT BOARD SCHEMATICS AND ASSEMBLY
DRAWiNGS"", ".,."", , " , , 1-1
APPENDIX II RECOMMENDED SPARE PARTS LIST , " .. , , 11-1
iii

LIST OF ILLUSTRATIONS
FIGURES
Figure
Number
Title of Figure
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
2-2
Hub Center Line and Track Locations 2-3
2-3 Cats Eye Pattern 2-4
2-4
Head Module Retaining and Cam Screws 2-5
2-5
Index-to-Data Burst .. " , 2-7
2-6
Index Sensor's Retaining Screw and Adjustment. 2-7
2-7 Negative Going Pulse Width 2-8
2-8
Track 00 Sensor 2-9
2-9
Optimum Head Azimuth Alignment. 2-11
2-10 Head Azimuth Alignment Acceptable Lower Limits 2-11
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 Point 7, 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
Title of Figure
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 Track 00 Sensor 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
Title of Table
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 Pin Assingments 1-13
Power Connector Pin Assignments 1-14
Options 1-17
Drive Interface Lines and Pin Connectors '" , 3-3
Stepper Logic Truth Table 3-5
v

SECTION I
INTRODUCTION TO THE TM848 FAMILY OF DISK DRIVES
1. INTRODUCTION
This section contains a description of the physical and functional specifications forthe TM848-1 and-
2 disk drives, 48 tracks per inch (TPI), manufactured by Tandon 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
capable of recording and reading digital data, using FM, and MFM.
1.2 PHYSICAL DESCRIPTION
OF THE DRIVE
The drive
can be mounted in any vertical or horizontal plane. However, when mounted horizontally,
the printed circuit board must be up.
The
spindle is belt driven by a brushless D.C. motor with an integral tachometer. The servo control
circuit, suitably sized pulleys, and the tachometer control the speed of the spindle. The Read/Write,
double-sided head assembly is positioned by means of a stepper motor, split band, and apulley.
The
Read/Write/Erase head assembly is a glass-bonded manganese/zinc ceramic structure. It has a
life in
excess of 20,000 hours.
For
diskette loading, operator access is provide via a slot located on the front of the drive.
The
electronic components of the drive are mounted on a circuit board assembly located in the
chassis. Power and interface signalsare routed 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
consists of a spindle drive system, ahead positioning system, and a read/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 number of heads. The circuit board is identical in both models.
When
the diskette lever is opened, access is provided for the insertion of a diskette. The diskette is
accurately positioned by plastic guides.The disk position is ensured by the backstop and disk ejector.
Closing the diskette lever activates the cone/clamp system, resulting in centering of the diskette and
clamping of the diskette to the drive hub.The drive hub is driven at a constant speed of 360 RPM by a
servo-controlled brushless D. 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 track by means of a stepper motor/band assembly and its
associated electronics. This positioner employs a3.6 degree rotation to cause a one-track linear
movement. When a write-protected diskette is inserted into the drive, the Write Protect sensor
disables the write electronics of the drive, and a Write Protect status output signal is available to the
interface.
When
performing a write operation, a 0.013-inch wide (nominal) data track is recorded. This track is
then tunnel erased to 0.012 inch (nominal).
Data recovery electronics include alow-level head amplifier, a differentiator, a zero crossing
detector, and digitizing circuits.
No data-clock separation is provided.
In addition,
the drive is supplied with the following sensor systems:
1. A track 00 sensor that senses when the Head Carriage Assembly is positioned at Track 00.
2. The two index sensors, each of which consists of aL.E.D. light source and a phototransistor,
are positioned so that asignal is generated when a index hole is detected. The drive can
determine whether asingle- or double-sided diskette is installed.This output signalis present
at the interface.
3. The Write Protect sensor disables the drive's write electronics whenever a write-enable tab is
removed from
the diskette (see Section 1.12).
1.4 DISKETTES
The drive
uses a standard eight-inch diskette. Diskette$ are available with a single index hole orwith
index and sector holes. They also are available double- or single-sided.
Single index hole diskettes are used when sector information is pre-recorded on the diskette (soft
sectoring).
Multiple index hole diskettes provide sector pulses by means of the index sensor and
electronics (hard sectoring).
1.5
MECHANICAL AND ELECTRICAL SPECIFICATIONS
The
mechanical and electrical specifications of the drive are listed in Table 1-1.
1.6 POWER REQUIREMENTS
The
power requirements of the drive are listed in Table 1-2.
1.7 INTERFACE CIRCUIT SPECIFICATIONS
The
interface circuits are designed so that a disconnected wire results in afalse signal.
Levels:
True =
+0.4 V, maximum
False =
+2.4 V, minimum
1.8
INCOMING INSPECTION CHECKS AND PROCEDURES
There are
two kinds of recommended incoming inspection checks and procedures: static and
dynamic ones.
The
static incoming inspection checks include the minimum steps that should be taken to ensure
that the drive is operational 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:
+24 V D. 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:
Number of Tracks:
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 ±5percent, 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°C to 46°C (40°F to 115°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
1in 10
9
bits
1in 10
12
bits
1in 10
6
seeks
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, Side 0, both models;
6818 FCI, Side 1, 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