Keithley 2520, Service Manual, Page: 75 / 137

Model 2520 Pulsed Laser Diode Test System Service Manual Troubleshooting 4-3
Power-on self-test
During the power-on sequence, the Model 2520 will perform a checksum test on its
EPROM and test its RAM. If one of these tests fails, the instrument will lock up.
Front panel tests
There are three front panel tests: one to test the functionality of the front panel keys and
two to test the display. In the event of a test failure, refer to
“Display board checks” on
page 4-13 for details on troubleshooting the display board.
KEYS test
The KEYS test lets you check the functionality of each front panel key. Perform the fol-
lowing steps to run the KEYS test.
1. Display the MAIN MENU by pressing the MENU key.
2. Using the EDIT keys, select TEST, and press ENTER to display the SELF-TEST
MENU.
3. Select DISPLAY-TESTS, and press ENTER to display the following menu:
FRONT PANEL TESTS
KEYS DISPLAY-PATTERNS CHAR-SET
4. Select KEYS, and press ENTER to start the test. When a key is pressed, the label
name for that key will be displayed to indicate that it is functioning properly. When
the key is released, the message “No keys pressed” is displayed.
5. Pressing EXIT tests the EXIT key. However, the second consecutive press of EXIT
aborts the test and returns the instrument to the SELF-TEST MENU. Continue
pressing EXIT to back out of the menu structure.
DISPLAY PATTERNS test
The display test lets you verify that each pixel and annunciator in the vacuum fluorescent
display is working properly. Perform the following steps to run the display test:
1. Display the MAIN MENU by pressing the MENU key.
2. Select TEST, and press ENTER to display the SELF-TEST MENU.
3. Select DISPLAY-TESTS, and press ENTER to display the following menu:
FRONT PANEL TESTS
KEYS DISPLAY-PATTERNS CHAR-SET