Keithley 2701 Service Manual

Model 2701 Service Manual Troubleshooting 4-13
Troubleshooting
Troubleshooting information for the various circuits is summarized below. See “Principles
of operation” on page 4-5 for circuit theory.
Display board checks
If the front panel DISP tests show a failure, troubleshoot the display board using Table 4-3.
Power supply checks
Power supply problems can be checked using Table 4-4.
Table 4-3
Display board checks
Step Item/component Required condition Remarks
1
2
3
4
5
6
7
Front panel DISP test
P1005, pin 5
P1005, pin 9
U401, pin 1
U401, pin 43
U401, pin 32
U401, pin 33
Verify that all segments operate.
+5V ±5%
+37V ±5%
Goes low briefly on power up, then
goes high.
4MHz square wave.
Pulse train every 1msec.
Brief pulse train when front panel
key is pressed.
Use front panel display test.
Digital +5V supply.
Display +37V supply.
Microcontroller RESET.
Controller 4MHz clock.
Control from main processor.
Key down data sent to main processor.
Table 4-4
Power supply checks
Step Item/component Required condition Remarks
1
2
3
4
5
6
7
8
9
10
11
Line fuse
Line voltage
Line power
+5VD pad
+3.3VD pad
+2.5VD pad
+1.8VD pad
U101, pin 7
U125, pin 3
U119, pin 3
U124, pin 3
Check continuity.
120V/240V as required.
Plugged into live receptacle, power on.
+5V ±5%
+3.3V ±5%
+2.5V ±5%
+1.8V ±5%
+37V ±5%
+15V ±5%
-15V ±5%
+5V ±5%
Remove to check.
Check power module position.
Check for correct power-up sequence.
+5VD, referenced to Common D.
1
+3.3VD, referenced to Common D.
1
+2.5VD, referenced to Common D.
1
+1.8VD, referenced to Common D.
1
+37V, referenced to Common D.
1
+15V, referenced to Common A.
2
-15V, referenced to Common A.
2
+5VRL, referenced to Common A.
2
1
U144, pin 2
2
C293 negative terminal

Keithley 2701 Specifications

General

Brand	Keithley
Model	2701
Category	Multimeter
Language	English