Table of Contents
Advertisement
Connect
the tracking
generator
to the
275A
right input.
Press the
SYNTHESIZE
FROM
RIGHT
button. Verify that the
corresponding red
lamp
lights.
Verify that
the
response
shown
in
Fig.
5-5
can
again be observed
at
the
275A
outputs.
2)
Control
Circuit
Bandpass
Filter
Performance
Verification
Leave
the tracking
generator connected
to
the
275A
right input.
Observe
TP7
with
the
spectrum
analyzer,
and
verify that the
swept
response
is
very close
to Fig. 5-6.
Repeat
for
the
right
channel,
connecting
the tracking
generator
to
the
275A
right
input
and observing TP8.
Fig. 5-6:
Control
Circuit
Bandpass
Filter
Response
(20-20kHz
log span,
lOdB/div)
3)
Automatic
Recognition
Circuit Tests
a.
Connect
the
oscillator to
a
panpot
(such as a
preamp
with
a
balance
control).
Connect
the
left
and
right
outputs
of
the
panpot
to
the
left
and
right inputs of
the
275A
respectively.
Set the
oscillator to
1kHz
and +4dBu.
Set the rear-panel
RECOGNITION
switch on the
275A
to
M/S+1CH.
b.
Temporarily
suppress
the oscillator's output.
First press the
275A's
SYNTH
FROM
LEFT
button.
Then
press the
AUTO
button. Verify that that the red
lamp
above
the
BYPASS
switch fades
in
over
a
2
second
interval
(approximately).
c.
Turn
the
panpot
full left.
Restore
the
oscillator,
and observe
that the red
lamp
above
SYNTH
FROM
LEFT
comes
on immediately.
Temporarily
suppress the
oscillator
by quickly fading
its
output
off,
and
verify
that the
lights
do
not
change
state.
5-5
Advertisement
Table of Contents
