Keithley 2000 Repair Manual

Display board checks
If the front panel DISP test indicates that there is a problem on the display board, use Table
2-2. See “Principles of Operation” for display circuit theory.
Power supply checks
Power supply problems can be checked out using Table 2-3. See “Principles of Operation”
for circuit theory on the power supply.
Table 2-2
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 pixels operate.
+5V +/-5%
+37V +/-5%
Goes low briefly on power up,
then goes low.
4MHz square wave.
Pulse train every 1msec.
Brief pulse train when front
panel key 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 2-3
Power supply checks
Step Item/component Required condition Remarks
1
2
3
4
5
6
7
8
Line fuse
Line voltage
Line power
U144, pin2
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%
+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.
+37V, referenced to Common D.
+15V, referenced to Common A.
-15V, referenced to Common A.
+5VRL, referenced to Common A.
Troubleshooting 2-11

Keithley 2000 Specifications

General

Digits	6.5
DC Voltage Range	100 mV to 1000 V
AC Voltage Range	100 mV to 750 V
Resistance Range	100 Ω to 100 MΩ
Connectivity	IEEE-488 (GPIB)
Display Type	VFD