Keithley 2010 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.
AC power is applied to the AC power module receptacle (J1009). Power is routed through the
line fuse and line voltage selection switch of the power module to the power transformer. The
power transformer has a total of four secondary windings for the various supplies.
AC voltage for the display filaments is taken from a power transformer secondary at F1 and
F2, and then routed to the display board.
Each DC supply uses a rectifier and a capacitive filter, and many supplies use an IC regulator.
Table 4-1 summarizes rectifier, filter, and regulator circuits for the various DC supplies.
Table 4-1
Power supply components
Supply Rectifier Filter Regulator
+5VD
+37V
+15V
-15V
+5V, +5VRL
+25V
-25V
+18V
-18V
+20V
CR104
CR116, CR117
CR102
CR102
CR103
CR136, CR140, CR141
CR137, CR138, CR139
CR102
CR102
–
C156, C175
C104
C148
C131
C146
C281
C284
–
–
C279, C281
U144
U101
U180
U179
U124
–
–
–
–
U187
4-4 Troubleshooting

Keithley 2010 Specifications

General

Frequency Range	3 Hz to 300 kHz
DC Voltage Range	100 mV to 1000 V
AC Voltage Range	100 mV to 750 V
DC Current Range	3 A
DC Current Accuracy	0.05%
AC Current Range	3 A
Resistance Accuracy	0.01%
Interface	GPIB, RS-232
Power Supply	50 Hz or 60 Hz