Fluke Series II User manual

For the benefit and convenience of its customers, Fluke
Corporation (Fluke) has reproduced this copy of amanual
which is no longer in production. This manual has not been
edited or updated since the revision date shown on the lower
left hand corner of the first page. Fluke will not be liable for
any claims, losses or damages of any kind incurred by any
user arising from use of this manual.
FLUKE
77/75/73/70/23/2
1
Series II Multimeter
Service Manual
PN 896204
July 1991 Rev. 1, 9/92
©1992 John Fluke Mfg., Inc. All rights reserved. Lltho in U.S.A. ®

OPERATOR SAFETY INFORMATION
This meter has been designed and tested according to IEC Publication 348. Follow all safety
and operating instructions to ensure that the meter is used safely and is kept in good
operating condition.
•Never use the meter if the meter or test leads look damaged.
•Always turn off power to the circuit before cutting, unsoldering, or breaking the circuit. Small
amounts of current can be dangerous.
•Never measure resistance in acircuit when power is applied to the circuit.
•Never touch the probes to avoltage source when the test leads are plugged into the 10A or
300 mA input jack.
•To avoid damage or injury, never use the meter on unprotected circuits that exceed 4800
volt-amps.
•Never apply more than 1000V dc or 750V ac rms (sine) between any input jack and earth
ground.
•Always be careful when working with voltages above 60V dc or 30V ac rms. Such voltages
pose a shock hazard.
•Always keep your fingers behind the finger guards on the probe when making
measurements.
•Always use a high voltage probe to measure voltage if the peak voltage might exceed
1000V.
SYMBOLS MARKED ON EQUIPMENT
DANGER -High voltage.
Attention -refer to the manual. This symbol indicates that information about
usage of afeature is contained in the manual.
Fuse information.
USE THE PROPER FUSE
To avoid fire hazard, use only afuse identical in type, voltage rating, and current rating as
specified on the case bottom fuse rating label.
DO NOT OPERATE DISASSEMBLED METER
Always operate the meter with case top and bottom properly assembled.
Access procedures and the warnings for such procedures are contained in this Service
Manual. Service procedures are for qualified service personnel only.
DO NOT ATTEMPT TO OPERATE IF PROTECTION MAY BE IMPAIRED
If the meter appears damaged or operates abnormally, protection may be impaired.
Do not attempt to operate it. When in doubt, have the meter serviced.

Table of Contents
SECTION TITLE PAGE
1Introduction and Specifications 1-1
1-1. INTRODUCTION 1-3
1-2. ORGANIZATION OF THE SERVICE MANUAL 1-3
1-3. CONVENTIONS 1-4
1-
4. SPECIFICATIONS 1-4
2Theory of Operation 2-1
2-
1. INTRODUCTION 2-3
2-2. FUNCTIONAL BLOCK DESCRIPTION 2-3
2-3. DETAILED DESCRIPTION 2-3
2-4. Voltage Signal Conditioning 2-3
2-5. Cunrent Conditioning 2-4
2-6. Ohms 2-4
2-7. Additional Circuitry 2-4
2-8. AC CONVERTER 2-4
2-9. ACTIVE FILTER 2-4
2-10. ROTARY SWITCH 2-5
2-
11. A/D CONVERSION 2-5
3Maintenance 3-1
3-
1. INTRODUCTION 3-3
3-2. PCAACCESS AND GENERAL MAINTENANCE 3-3
3-3. DISPLAY ACCESS 3-4
3-4. CLEANING 3-4
3-5. PERFORMANCE TESTS 3-6
3-6. Initial Procedure 3-6
3-7. Display Test 3-6
3-8. DC Voltage Test 3-6
3-9. AC Voltage Test 3-7
3-10. Resistance Test 3-8
3-11. Diode Test 3-8
3-12. DC mA Test (75/21 &77/23 Only) 3-9
3-13. DC Amps Test (73, 75/21, and 77/23 Only) 3-9
3-14. CALIBRATION 3-9
3-15. TROUBLESHOOTING 3-9
3-16. Supplemental Troubleshooting Procedures 3-11

Table of Contents
SECTION TITLE PAGE
3-17. CHECKING THE CRYSTAL OSCILLATOR 3-11
3-18. CHECKING THE REFERENCE VOLTAGE 3-11
3-19. CHECKING DISPLAY DRIVE VOLTAGE 3-11
3-20. CHECKING BEEPER DRIVE SIGNAL 3-11
3-
21. TRACING THE VDC SIGNAL PATH 3-11
4List of Replaceable Parts 4-1
4-
1. INTRODUCTION 4-3
4-2. HOW TO OBTAIN PARTS 4-3
4-3. TECHNICAL SERVICE CENTERS 4-3
5Schematic Diagrams 5-1
ii

List of Tables
TABLE TITLE PAGE
1-
1. Specifications 1-5
2-
1. SI Function Codes 2-6
3-
1. Recommended Test Equipment 3-4
3-2. DC Voltage Test 3-7
3-3. AC Voltage Test 3-7
3-4. Resistance Test 3-8
3-5. DC mA Test 3-9
3-6. DC Amps Test 3-9
5-1. Abbreviations 5-2
Hi

List of Tables
IV

List of Illustrations
FIGURE TITLE PAGE
2-1. Overview 2-3
2-2. Ohms Function 2-5
2-
3. AC and A/D Converter 2-7
3-
1. Assembly Details 3-5
3-2. Display 3-6
3-3. Troubleshooting Tree 3-10
5-1. A1 Main PCA 5-3
5-2. Signal Flow Diagram 5-5
v

List of illustrations

Section 1
Introduction and Specifications
CONTENTS PAGE
1-1. INTRODUCTION 1-3
1-2. ORGANIZATION OF THE SERVICE MANUAL 1-3
1-3. CONVENTIONS 14
14. SPECIFICATIONS 14
1-1

Introduction and Specifications