4.32 - CHANNEL AND AMPLITUDE DAC TEST
1. Select the CHANNEL TEST by pressing the YES switch when
the
TEST ANY CHANNEL?
is
displayed.
r .
2. Select audio output muted
3. Select C2 sinewave at SkHz sampling rate
4. Enable channels 1 through 12, ramp amplitude DACs, Group A
S.
Use
an
oscilloscope and probe the test points indicated
in
Table 2 or 3 to verify channel operation. Probe the test
points indicated in Table . 4 ot
verify
Amplitude
DAC
operation.
NOTE:
Use caution when
probing
pin 7
of
the
amp DAC
opamps,
because
pin
8
is
a
power
pin.
If
the
scope
probe
shorts
pin
7
to
pin 8
the
opamp will be damaged.
The frequency of the sinewave will vary depending upon the
sampling rate selected. Table
1 shows the
12
possible frequencies
available. The time
(T).
shown
in
Table 1 indicates the period of each
sinewave. Figure 1 shows how the sinewave should appear at the
outputs of the alias filters (See Table 2).
TABLE
1:
SINEWAVE
PERIOD
TIMES
(T)
SAMPLI
NG
RATE
C2
C5
5kHz
15
ms
3,8
ms
10kHz
7.5
ms
1.9
ms
15kHz 5.0
ms
1.25
ms
25kHz
3.0
ms
0.75
ms
Kurzweil
250
Service Manual, Chapter 4
4-65
C8
0,7
ms
,35
ms
0.25
ms
0.15
ms
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