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M aintenance— 2440 S ervice
T R IG 'D
|
= 2 ° = 1
READY
|
= 2 1 = 2
ARM
|
= 2 2 = 4
G
O
II
C
O
O
J
II
+
—
|
= NOT USED
4 9 1 7 - 3 2
Figure 6*4. Trigger LED binary coding for diagnostic tests.
again. If a failure prevents display of the EXT DIAG menu,
you must turn off the scope and turn it back on again to
rerun the tests. It takes a little practice to read the failure
codes from the LEDs.
If it can, the scope displays the Extended Diagnostics
menu if a failure is found (or if the Self Diagnostics were
run from that menu). The display of test selections in the
Extended Diagnostics menu is a hierarchically structured
set of tests in lists containing the test numbers, test
names, and last status of the test results. If the test has
not been run since the last COLD START, no status will
be displayed. If an upper level test in the set (such as
REG) is run, all tests in the REG test hierarchy will be
done and labeled with a PASS or FAIL status. Menu
operation is covered in “Diagnostics Operation’ .
2. The LED’s flash, indicating that tests are being run.
3.
When the test failure occurs, all the Trigger LEDs are
lighted and held on momentarily, indicating a failure has
been found.
4.
For the first number of the failed test, the READY
LED turns on for a binary 2 (the failed test is in the 2000
level); all the LEDs are then turned on to delimit the first
digit of the failed test from the second digit to follow.
D iagnostics O peration
Diagnostics are runnable from the front-panel or via the
GPIB. The Self-Diagnostics are also executed when the
instrument is powered up. For both the Self and Extended
Diagnostics,
front-panel
access
is
from
the
same
CAL/DIAG menu used to access the calibration features:
< s ta tu s >
< s ta tu s >
< s ta tu s >
< w a rm -u p >
SELF
EXT
SELF
EXT
CAL
CAL
DIAG
DIAG
5.
The second number of the test number (one) is
shown by turning on the T R IG ’D LED for the binary code
for 1, then all the LEDs are again turned on as the code
digit delimiter.
6.
The third number of the failed test (three) is shown
by turning on both the T R IG ’D and the READY LEDs.
Their binary values are summed (1 + 2) to obtain the third
number of the failed test (three), and all the LEDs are
again lit to separate the digits.
7.
The fourth and final number of the failed test is 0,
and all the LEDs light to identify the end of the failed
test code.
8.
After flashing out the coded number of the first failed
test, the diagnostics continue on with the remaining tests,
if they can be run. Any additional failures found will NOT
be flashed on the Trigger LEDs.
If you miss the code the first time (as is usual unless
you are expecting a failure), Self Diagnostics must be run
Pushing SELF DIAG or powering up the scope causes
the Self Diagnostics to run. These routines take about 30
seconds. First the TRIGGER status LED’s flash as previ
ously described. Then, if all tests are passed, the scope
displays the main EXT DIAG menu if SELF DIAG was run
from that menu, or returns to scope mode at power-down
if SELF DIAG was run due to power-on. If passed when
run from the CAL/DIAG menu, the scope returns to that
menu and indicates the PASS status above the SELF
DIAG button label. Failure of a test always returns the
EXT DIAG menu regardless of what caused the SELF
DIAG to run. The EXT DIAG menu is exited by pressing
the
MENU
OFF/EXTENDED
FUNCTIONS
front-
panel button.
DIAGNOSTIC MENUS. Since the diagnostics routines
are layered into a multi-level, hierarchical structure, the
diagnostic menus are also layered this way. In each menu,
there is one higher level test displayed, along with several
equal sublevels. The menus are used to either run the
higher (top) level test or to select a menu for one of the
sublevels displayed. The select sublevel test can then be
run as the top level of the submenu selected. Examination
of the EXT DIAG menu should illustrate the structure:
6 -2 9
Summary of Contents for 2440
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Page 136: ...Theory of Operation 2440 Service Figure 3 15 PWM Regulator and Inverter 3 94 ...
Page 138: ...Theory of Operation 2440 Service Figure 3 16 PWM switching waveforms 3 96 ...
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Page 455: ...W A V EFO R M S FOR D IAG RAM 11 WAVEFORMS FOR DIAGRAM 11 6603 29 ...
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