Keithley SourceMeter 2425, Service Manual

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Model 2425 Service Manual Troubleshooting 4-5
Principles of operation
The following information is provided to support the troubleshooting tests and procedures
covered in this section of the manual. Refer to the following drawings:
Figure 4-1 — Overall block diagram
Figure 4-2 — Analog circuitry block diagram
Figure 4-3 — Power supply block diagram
Figure 4-4 — Output stage simplified schematic
Figure 4-5 — Digital circuitry block diagram
Overall block diagram
Figure 4-1 shows an overall block diagram of the Model 2425. Circuitry may be divided
into three general areas:
• Analog circuits — includes sourcing circuits such as the DACs, clamps, output
stage, and feedback circuits, as well as measurement circuits such as the A/D con-
verter.
• Digital circuits — includes the microcomputer that controls the analog section,
front panel, and GPIB and RS-232 ports, as well as associated interfacing circuits.
• Power supplies — converts the AC line voltage into DC voltages that supply the
power for the digital and analog circuits, and the output stage.