Troubleshooting; Display Board Checks - Keithley 2520 Service Manual

Model 2520 Pulsed Laser Diode Test System Service Manual

Troubleshooting

Troubleshooting information for the various circuits is summarized below. Refer to the
component layout drawings at the end of

Display board checks

If the front panel display tests indicate that there is a problem on the display board, use
Table
Table 4-1
Display board checks
Item/
Step component
1 Front panel test
2 J1033
3 U902, pin 1
4 U902, pin 43
5 U902, pin32
6 U902, pin 33
4-1. See "Principles of operation" on page 4-4
Required condition
Verify that all segments operate.
+5V, ±5%
Goes low briefly on power up, and
then goes high.
4MHz square wave.
Pulse train every 1 ms.
Brief pulse train when front panel key
is pressed.
Section 6 for component locations.
for display circuit theory.
Remarks
Use front panel display test.
Digital +5V supply.
Microcontroller RESET.
Controller 4MHz clock.
Control from main processor.
Key down data sent to main processor.
Troubleshooting 4-13