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his manual presents service information for the Fluke 73, 75, and 77 Multimeters. Included are a theory of operation, general maintenance procedures, performance tests, calibration procedures, troubleshooting information, a list of replaceable parts, and a schematic diagram. INTRODUCTION AND SPECIFICATIONS ... 1-1 1-1. INTRODUCTION ... 1-1 1-2. SPECIFICATIONS ... 1-1 2 OPERATING INSTRUCTIONS ... 2-1 2-1. INTRODUCTION ... 2-1 3 THEORY OF OPERATION ... 3-1 3-1. INTRODUCTION ... 3-1 3-2. OVERVIEW ... 3-1 3-3. DETAILED DESCRIPTION ... 3-1 3-4. Input Signal Conditioning ... 3-1 3-5. Ohms Input Protection ... 3-1 3-6. Additional Circuitry ... 3-1 4 MAINTENANCE ... 4-1 4-1. INTRODUCTION ... 4-1 4-2. PWB ACCESS AND GENERAL MAINTENANCE ... 4-1 4-3. DISPLAY ACCESS ... 4-2 4-4. CLEANING ... 4-2 4-5. PERFORMANCE TESTS ... 4-3 4-6. Initial Procedure ... 4-3 4-7. Display Test ... 4-3 4-8. AC Voltage Test ... 4-3 4-9. DC Voltage Test ... 4-3 4-10. Resistance Test ... 4-3 4-11. Diode Test ... 4-4 4-12. DC mA Test (75 & 77 Only) ... 4-4 4-13. DC Amps Test ... 4-4 4-14. CALIBRATION ... 4-5 4-15. TROUBLESHOOTING ... 4-5 4-16. Overall System Check ... 4-5 4-17. VDC Signal Tracing ... 4-5 5 LIST OF REPLACEABLE PARTS ... 5-1 5-1. INTRODUCTION ... 5-1 5-2. HOW TO OBTAIN PARTS ... 5-1 6 GENERAL INFORMATION ... 6-1 6-1. INTRODUCTION ... 6-1 7 SCHEMATIC DIAGRAMS ... 7-1 8 MANUAL CHANGE INFORMATION ... 8-1 ii

Instruction Sheet

ORGANIZATION OF THE SERVICE MANUAL 1-2. The following descriptions briefly describe each section in the manual. SECTION 1. INTRODUCTION AND SPECIFICATIONS This section describes use of the Service Manual and application of special terminology (conventions) to describe the meter’s circuitry. A complete set of specifications appears at the end of this section. SECTION 2. THEORY OF OPERATION This section first categorizes instrument circuitry into functional blocks, with a description of each block’s role in overall operation. A detailed circuit description is then given for each block. These descriptions explore operation to the component level and fully support troubleshooting and repair procedures defined in Section 3. SECTION 3. MAINTENANCE Provides complete maintenance information, from general maintenance and cleaning instructions to detailed troubleshooting and repair procedures to the component level. Troubleshooting and repair procedures rely heavily on both the Theory of Operation presented in Section 2 and the Schematic Diagrams shown in Section 5. SECTION 4. LIST OF REPLACEABLE PARTS Includes parts lists for all standard assemblies. Information on how and where to order parts is also provided. SECTION 5. SCHEMATIC DIAGRAMS Includes schematic diagrams for all assemblies.

The following descriptions briefly describe each section in the manual. SECTION 1. INTRODUCTION AND SPECIFICATIONS This section describes use of the Service Manual and application of special terminology (conventions) to describe the meter’s circuitry. A complete set of specifications appears at the end of this section. SECTION 2. THEORY OF OPERATION This section first categorizes instrument circuitry into functional blocks, with a description of each block’s role in overall operation. A detailed circuit description is then given for each block. These descriptions explore operation to the component level and fully support troubleshooting and repair procedures defined in Section 3. SECTION 3. MAINTENANCE Provides complete maintenance information, from general maintenance and cleaning instructions to detailed troubleshooting and repair procedures to the component level. Troubleshooting and repair procedures rely heavily on both the Theory of Operation presented in Section 2 and the Schematic Diagrams shown in Section 5. SECTION 4. LIST OF REPLACEABLE PARTS Includes parts lists for all standard assemblies. Information on how and where to order parts is also provided. SECTION 5. SCHEMATIC DIAGRAMS Includes schematic diagrams for all assemblies.