Operating instructions

OPTIMOD-AM DIGITAL MAINTENANCE
4-9
(1) + unreg. (3) digital gnd (5) +15V (7) +5 V digital (9) –5V analog
(2) - unreg (4) chassis gnd (6) -15V (8) +5V analog (10) NC
Table 4-2: Layout Diagram of J7, with expected voltages on each pin
The +3.3V and +2.5V supplies are locally regulated on the DSP and base
boards (see Section 6).
C) Measure the regulated voltages at J7 with the DVM and observe the ripple
with an oscilloscope, AC-coupled. The following results are typical:
Power Supply Rail DC Voltage (volts) AC Ripple (mV p-p)
+15VDC
+15  0.5
<20
–15VDC
–15  0.5
<20
+5VDC
+5  0.25
<20
–5VDC
–5  0.25
<20
Digital +5VDC
+5  0.25
[Obscured by noise]
Table 4-3: Typical Power Supply Voltages and AC Ripple
3. Adjust Analog Output Level Trim.
A) Verify 9400 software controls are set to their default settings. [Refer to step
(1.B) on page 4-7.]
B) Feed the 9400 output with the built-in 400 Hz test tone:
a) Navigate to S
ETUP > TEST.
b) Set the M
ODE to TONE.
C) Connect the audio voltmeter to the Left Analog Output.
D) Adjust output trim VR200 to make the meter read +10.6 dBu. (0 dBu = 0.775V
rms.) Verify a frequency reading of 400 Hz.
E) Verify THD+N reading of <0.05% (0.02% typical) using a 22 kHz low pass filter
in the distortion analyzer.
F) Set the M
ODE to BYPASS.
BYPASS defeats all compression, limiting, and program equalization but
retains pre-emphasis.
G) Verify a reading (noise) of <–80 dBu at the output of the unit.
H) Using VR201, repeat steps (C) through (G) for the Right Analog Output.
4. Check frequency response of Analog I/
O.
A) Verify 9400 software controls are set to their default settings. [Refer to step
(1.B) on page 4-7.]
B) Be sure y
ou are still in B
YPASS mode [see step (3.F)].
C) Connect the oscillator to the Left Analog Input XLR connector.