Keithley 2750 Service Manual

4-4 Troubleshooting Model 2750 Multimeter/Switch System Service Manual
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 block diagrams:
Figure 4-1 — Power supply block diagram.
Figure 4-2 — Digital circuitry block diagram.
Figure 4-3 — Analog circuitry block diagram.
Power supply
The following information provides some basic circuit theory that can be used as an aid to
troubleshoot the power supply. A block diagram of the power supply is shown in
Figure 4-1.
Figure 4-1
Power supply block diagram
Fuse
Power
Switch
Line
Voltage
Select
Switch
Power
Transformer
CR103
C146
U124
CR104
C156, C175
C281, U144
C273, C274
CR116, CR117
C104, U101
CR102, CR115
C131, C148
U119, U125
+5VD
D Common
+37V
D Common
+15.7V
-15.7V
+5V
A Common
A Common
+18V
-18V

Keithley 2750 Specifications

General

Interface	GPIB, RS-232, Ethernet
Switching Speed	Up to 500 channels/second
Maximum Voltage	300V
Operating Temperature	0°C to 50°C
Measurement Functions	DCV, ACV, DCI, ACI, 2-wire Resistance, 4-wire Resistance, Frequency, Temperature
Resolution	6.5 digits
Current	1A
Maximum Current	1A