4-4 Troubleshooting Model 2500 Service Manual
4. Select DISPLAY-PATTERNS, and press ENTER to start the display test. There are 
five parts to the display test. Each time a front panel key (except EXIT) is pressed, 
the next part of the test sequence is selected. The five parts of the test sequence are 
as follows:
• Checkerboard pattern (alternate pixels on) and all annunciators.
• Checkerboard pattern and the annunciators that are on during normal 
operation.
• Horizontal lines (pixels) of the first digit are sequenced.
• Vertical lines (pixels) of the first digit are sequenced.
• Each digit (and adjacent annunciator) is sequenced. All the pixels of the 
selected digit are on. 
5. When finished, abort the display test by pressing EXIT. The instrument returns to 
the FRONT PANEL TESTS MENU. Continue pressing EXIT to back out of the 
menu structure. 
CHAR SET test
The character set test lets you display all characters. Perform the following steps to run the 
character set 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
4. Select CHAR-SET, and press ENTER to start the character set test. Press any key 
except EXIT to cycle through all displayable characters.
5. When finished, abort the character set test by pressing EXIT. The instrument 
returns to the FRONT PANEL TESTS MENU. Continue pressing EXIT to back 
out of the menu structure. 
Principles of operation
The following information is provided to support the troubleshooting tests and procedures 
covered in this section of the manual. Refer to the following drawings: 
Figure 4-1 — Overall block diagram
Figure 4-2 — Analog circuitry block diagram
Figure 4-3 — Power supply block diagram
Figure 4-4 — Digital circuitry block diagram