Operating instructions

4-12
MAINTENANCE ORBAN MODEL 9400
previous tests may fail to detect faults in certain DSP chips. To verify that all of
the DSP chips are working correctly:
a) Connect the oscillator to both 9400’s analog inputs.
b) Navigate to S
ETUP > TEST and set the 9400’s operating mode to OPERATE.
c) Recall the G
EN MED preset.
d) Set the oscillator’s frequency to 400 Hz and its output level to create 10 dB
of gain reduction as indicated on the AGC
MASTER gain reduction meter.
e) Connect the N&D test set to the 9400’s left Analog Output #1.
f) Navigate to S
ETUP > IO CALIB > OUTPUT > ANALOG1 > SOURCE and set the
9400’s left Analog Output #1 to emit the analog AM signal.
g) Verify that combined noise and distortion are below 0.1%.
h) Repeat steps (f) and (g) for the right Analog Output #1.
i) Navigate to S
ETUP > IO CALIB > OUTPUT > ANALOG1 > SOURCE and set the
9400’s left Analog Output #1 to emit the digital radio AM signal.
j) Verify that combined noise and distortion are below 0.1%.
k) Repeat steps (i) and (j) for the right Analog Output #2.
9. Return OPTIMOD-AM to service.
A) Remove the 600 resistors connected across the outputs.
B) Restore your normal operating parameters, using the notes you made in
step
(1.B) on page 4-7.
C) Navigate to S
ETUP > TEST > MODE and choose OPERATE.
D) Recall your normal operating preset.