This manual covers servicing information for Fluke multimeter Models 83, 85, and 87 that are marked with CAT III 1000V on the top case and C € on the bottom case. These markings indicate that the multimeter complies with IEC-1010 Category III, 1000V fuse rating. This service manual will prove useful for tasks ranging from routine maintenance to troubleshooting and repair. Specifications, theory of operation, calibration routines, testing and troubleshooting procedures, parts replacement information, and schematic diagrams are provided. A meter under warranty will be promptly repaired or replaced (at Fluke's option) and returned at no charge. 1-2. Organization of the Service Manual The following descriptions for the various sections serve to introduce the manual. Section 1. Introduction and Specifications This section describes both 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 closely 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. A list of mnemonic definitions is also included to aid in identifying signal name abbreviations.