Maintenance Section 5
5-5
adjustment procedure. After the instrument has been
adjusted, perform the performance tests again to verify
instrument operation. The following inspection procedure
shall be used to locate obvious malfunctions within the
Audio Analyzer.
a. Inspect all external surfaces of Model 1121A for
physical damage, breakage, loose or dirty contacts, and
missing components.
Hazardous voltages are present when covers are
removed. Where maintenance can be performed without
having power applied, power should be removed.
b. Remove covers and shields as required to gain
access to components.
c. Inspect CBA surfaces for discoloration, cracks,
breaks, and warping.
d. Inspect CBAconductors for breaks, cracks, cuts,
erosion, or looseness.
e. Inspect all assemblies for burnt or loose com-
ponents.
f. Inspect all chassis-mounted components for
looseness, breakage, and loose contacts or conducts.
g. Inspect equipment for disconnected, broken,
cut, loose, or frayed cables or wires.
5-18. PERFORMANCE TESTS.
5-19. The performance tests should be performed about
every 12 months or after the instrument has been
repaired. The performance tests may also be performed
when the instrument is first received to verify instrument
performance.
5-20. Initial Calibration. Calibrate the instrument as
follows:
a. Set the LINE ON/OFF switch to ON and depress
the LCL/INIT key to initialize the instrument.
b. Enable the Analyzer input floating mode.
c. Connect the 50 Hz - 50 kHz Calibrator output to the
Analyzer HI and LOW input terminals using the balanced
cable and adapters.
d. Set the Calibrator to a frequency of 1 kHz and a
level of 3.000 volts and enable the Calibrator output.
e. After the Analyzer measurement settles, enter
special function 20 to calibrate full scale AC level. The
SOURCE display will indicate the - CAL - message
momentarily and any errors will be reported. The cali-
bration will take approximately 2 seconds after which the
SOURCE display will indicate special function 10.
f. If any of the optional filters are installed, set the
Calibrator to the reference frequency and level listed in
Table 5-2 designated for the filter to be calibrated and
enable the Calibrator output.
g. Enter the special function that corresponds to the
filter position to be calibrated. Special function 21 will
calibrate the optional filter No. 1 installed in the left-most
position while special function 22 calibrates optional filter
No. 2 installed in the right-most position. The SOURCE
display will indicate the - CAL - message momentarily and
any errors will be reported. The calibration will take
approximately 1 second after which the SOURCE display
will indicate special function 10.
h. Set the Calibrator to a level of 0.000 volts DC and
depress the Analyzer DC key to enable the DC level
measurement mode.
i. After the Analyzer measurement settles, enter
special function 23 to calibrate DC level offset. The
SOURCE display will indicate the - CAL - message
momentarily and any errors will be reported. The cali-
bration will take approximately 2 seconds after which the
SOURCE display will indicate special function 10.
j. Set the Calibrator to a level of 3.000 volts DC.
k. After the Analyzer measurement settles, enter
special function 24 to calibrate full scale DC level. The
SOURCE display will indicate the - CAL - message
momentarily and any errors will be reported. The cali-
bration will take approximately 1 second after which the
SOURCE display will indicate special function 10.
5-21. Analyzer DC Level Accuracy. Depress the LCL/
INIT key to initialize the instrument. After the initialization
sequence is complete, enable the input floating mode,
enable the DC low-pass filter and enter special function
17 to enable the slow detector mode. Connect the DC
Calibrator output using the balanced cable and adapters
to the Analyzer HI and LOW input terminals. Enter the
Calibrator settings listed in Table 5-3 and record the
Analyzer DC level readings.
5-22. Analyzer AC Level Accuracy. Depress the LCL/
INIT key to initialize the instrument, enable the input
floating mode and enter special function 17 to enable the
slow detector mode. Connect the 50 Hz - 50 kHz
Calibrator output using the balanced cable and adapters
to the Analyzer HI and LOW input terminals. Enter the
Calibrator settings listed in Table 5-4 and record the
Analyzer AC level readings.
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