TB 9-4931-413-50
SECTION III
6. Preliminary Instructions
a. Personnel should become familiar with the entire bulletin before beginning the
b. Remove protective cover from test instrument only when necessary for adjustment.
NOTE
Steps c and d below pertain only to model 1551-C with ac
power supply.
c. Connect test instrument to 115-volt ac source.
d. Set test instrument power supply POWER switch to on (up) position.
NOTE
Step e below is for model 1565-A only; steps f and g below are
for battery-powered model 1551-C only.
e. Turn test instrument left-hand knob to BAT. Meter pointer will indicate in region
marked BAT. If not, replace batteries.
f. Energize test instrument by lifting microphone holder to vertical position.
g. Turn METER BATTERIES switch to FIL 1, FIL 2 and PL, respectively. Meter
pointer will indicate in region marked BAT. If not, replace appropriate batteries.
NOTE
Throughout this bulletin, references to model 1565-A panel
markings and values are enclosed in parenthesis.
NOTE
Unless otherwise specified, verify the results of each test and
take corrective action whenever the test requirement is not
met before continuing with the calibration.
7. Sound-Level Meter Sensitivity
a. Performance Check
NOTE
Test instrument must be calibrated in an area where ambient
noise is less than 70 db.
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