Table Of Contents - HP 7925D Service Manual

Section I Page
THEORY OF OPERATION.
Introduction 1-1
Addressing Structure 1-1
Addressing Modes 1-2
Surface Mode 1-2
Cylinder Mode 1-2
Sector Format : 1-3
Functional Description 1-5
I/O Control System 1-6
Tag Bus Logic 1-6
Control Bus Logic 1-9
Select Logic 1-9
Unit Identity Logic 1-10
Status Logic 1-10
Attention Logic 1-11
Spindle Rotation System 1-12
Spindle Logic Initialization 1-12
Door Control Logic , 1-12
Run Spindle Command Logic 1-12
Phase Encoding and Decoding 1-12
Speed Control 1-13
Motor Current Regulation 1-13
Dynamic Braking 1-15
Speed Down Detection 1-15
Overcurrent Protection 1-15
Overvoltage Protection 1-15
Head Positioning System 1-15
Initial Head Load Operation 1-15
Normal Head Unload Operation 1-19
Seek Operation 1-20
Offset Operation 1-21
Recalibrate Operation 1-22
Emergency Retract Operation 1-23
Sector Sensing System 1-23
Read/Write System 1-24
Head Selection 1-24
Read Mode Operation 1-25
Write Mode Operation 1-25
Read/Write Fault Detection 1-26
Fault Detection System 1-26
Illegal Address Detection 1-26
Timeout Fault Detection '" 1-27
AGC Fault Detection 1-28
Carriage Back Fault Detection 1-28
Interlock Fault Detection 1-28
Read/Write Fault Detection 1-28
Air Circulation and Filtration System 1-30
Power Distribution System 1-32
Power Panel Assembly 1-32
Power Supply Assembly 1-32
Voltage Regulator Circuits 1-32
Voltage Protection Circuits 1-32
Supply Voltage Distribution 1-32
CONTENTS
I
Section II Page
MAINTENANCE
Introduction 2-1
Maintenance Precautions 2-1
Service Tools and Test Equipment 2-1
Standard Tools ., 2-1
Standard Test Equipment 2-1
Special Tools 2-1
Special Test Equipment 2-2
DSU Controls and Indicators , 2-5
DSU Operation 2-6
Preventive Maintenance , 2-7
General Cleaning Information 2-7
Preliminary Steps 2-7
Servicing the Air Circulation System 2-8
Pack Lock Lubrication 2-8
Cleaning Data and Servo Heads 2-10
Cleaning Carriage Rails and Bearings 2-10
Cleaning the Spindle Assembly
and Pack Chamber Assembly 2-12
Section III Page
ALIGNMENT AND ADJUSTMENT
Introduction 3-1
Service Adjustments not Requiring the DSU 3-1
Door Lock Assembly 3-1
Door Unlock Solenoid 3-1
Door Closed and Door Locked Switches 3-1
Carriage Latch and Detector Assembly 3-2
Head Cam Alignment 3-2
Service Adjustments Requiring the DSU 3-2
Installing the DSU 3-3
Exercising the Disc Drive 3-4
Velocity Command Gain Adjustment 3-5
Head Alignment Procedures 3-6
Warmup 3-7
Circumferential Alignment Check 3-7
Circumferential Alignment 3-8
Track Follower Alignment 3-9
Servo Head Alignment
I • • • • • • •
3-9
Data Head Alignment Check 3-19
Data Head Alignment 3-20
On-Line Checkout 3-21
Section IV Page
TROUBLESHOOTING
Diagnostic Test Programs 4-1
Troubleshooting Flowcharts 4-1
Power Sources 4-1
Visual Indication of Drive Status 4-2
Disc Service Unit 4-2
System Functional Diagrams 4-2
Wiring Connections 4-2
Power Distribution 4-2
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