5-2
5. Whenever a circuit board is removed or a component is
replaced, the Model 6517A must be recalibrated.
5.3
Power-on test
During the power-on sequence, the Model 6517A will per-
form a checksum test on its ROMs (U637 and U638) and test
its RAM ( U635 and U636). A ROM OK or RAM OK mes-
sage will be displayed upon successful completion. Howev-
er, if one of these tests fail, the instrument may lock up
completely.
5.4
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 paragraphs 5.5.1 and 5.6.1 for
details on troubleshooting the display board.
5.4.1 KEYS test
The KEYS test allows you to check the functionality of each
front panel key. Perform the following steps to run the KEYS
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 FRONT-PANEL-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 dis-
played 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 press-
ing EXIT to back out of the menu structure.
5.4.2 DISPLAY PATTERNS test
The display test allows you to verify that each pixel and an-
nunciator in the vacuum fluorescent display is working prop-
erly. 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 FRONT-PANEL-TESTS, and press ENTER to
display the following menu:
FRONT PANEL TESTS
KEYS DISPLAY-PATTERNS CHAR-SET
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:
a.
Checkerboard pattern (alternate pixels on) and all
annunciators.
b. Checkerboard pattern and the annunciators that are
on during normal operation.
c.
Horizontal lines (pixels) of the first digit are
sequenced.
d. Vertical lines (pixels) of the first digit are
sequenced.
e.
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 SELF-TEST MENU. Con-
tinue pressing EXIT to back out of the menu structure.
5.4.3 Character set test
You can also display the character set as follows:
1. Display the MAIN MENU by pressing the MENU key.
2. Select TEST, and press ENTER to display the SELF-
TEST MENU.
3. Select FRONT-PANEL-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 display the
character set.
5. Press any key except EXIT to cycle through the charac-
ter set displays.
6. Press EXIT to halt the test and return to the self-test
menu.
5.5
Principles of operation
The following paragraphs provide a brief overview of oper-
ating principles for each major circuit section of the Model
6517. Figure 5-1 shows an overall block diagram of the
instrument.