Keithley 2015, Service Manual

Page: 69 / 158

4-6 Troubleshooting
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
Figure 4-4 — Distortion digital circuitry block diagram
Figure 4-5 — Distortion analog circuitry block diagram
Figure 4-6 — Sine generator 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
CR104
C128, C156
U144
+5VD
+37V
+5VD2
+15V
+5V, +5VRL
D Common
D Common
D Common
+15VF
F Common
-15VF
+5VF
-15V
A Common
A Common
CR103
C146
U124
CR301
C350
U331
CR330
CR331
C562
C565
C568
U348
U349
U350
CR116, CR117
C104, C108
U101
CR102
C131, C148
U119, U125
Fuse
Power
Switch
Line
Voltage
Switch
Power
Transformer
Power
Transformer