Troubleshooting; Display Board Checks; Power Supply Checks - Keithley 2700 Service Manual

Troubleshooting

Troubleshooting information for the various circuits is summarized below. See "Principles
of operation" for circuit theory.

Display board checks

If the front panel DISP test indicates that there is a problem on the display board, use
Table 4-2.
Table 4-2
Display board checks
Step Item/component
1 Front panel DISP test
2 P1005, PIN 5
3 P1005, PIN 9
4 U401, PIN 1
5 U401, PIN43
6 U401, PIN 32
7 U401, PIN 33

Power supply checks

Power supply problems can be checked using
Table 4-3
Power supply checks
Step Item/component
1 Line fuse
2 Line voltage
3 Line power
4 U144, pin 3
5 U101, pin 7
6 U125, pin 3
7 U119, pin 3
8 U124, pin 3
1
TP106
2
C148 negative terminal
Required condition
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.
Required condition
Check continuity.
120V/240V as required.
Plugged into live receptacle, power on.
+5V ±5%
+37V ±5%
+15.7V ±5%
-15.7V ±5%
+5V ±5%
Troubleshooting
Remarks
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 4-3.
Remarks
Remove to check.
Check power module position.
Check for correct power-up sequence.
+5VD, referenced to Common D.
+37V, referenced to Common D.
+15V, referenced to Common A.
-15V, referenced to Common A.
+5VRL, referenced to Common A.
4-11
1
1
2
2
2