IN THE CASE OF THE DUAL-CHANNEL 622B, THE TEST
PROCEDURE BELOW
SHOULD BE FOLLOWED FROM
BEGINNING
TO END FOR CHANNEL
"A", THEN
REPEATED
FOR CHANNEL "B".
I) Signal Passage
Test
a) Connect the high
(+)
side of the
622 main
output to
the
input of the
harmonic
distortion
analyzer,
and
also to the vertical input of the
oscilloscope. Connect
the
ground side
of the
622
to
instrument ground.
b)
Ground the (-) input of the 622 and connect the output of the low-distortion
oscillator
to the
(+)
input of the
622.
c) Move
a||
IN/OUT
switches
to
OUT,
and center all EQ controls.
d)
Adjust
the
GAIN
control clockwise, and verify that an undistorted sinewave
appears at the
output.
e) Continue
to
advance the
GAIN
control until clipping
is
barely visible. Verify
that
this clipping level exceeds +l9dBm
for
20Hz, IkHz,
and
20kHz
input
signals.
f) Verify
that the
OVERLOAD
lamp flashes
at, or slightly below, the clipping
level
at
IkHz.
2)
DC Offset
a)
Disconnect the
oscillator from the 622 input.
b)
Move the
CHANNEL IN/OUT
switch
to
IN.
Measure the DC voltage
appearing at the output
of
the 622. The voltage
should not exceed 30mV DC.
3)
Distortion
and
Inverting
Operation
a)
Ground
the
(+)
input
of
the 622
and
connect
the low-distortion
oscillator to
the
(-) input
of
the 622.
Adjust the oscillator to IkHz.
b)
Center all
operating controls, and move
al]
BAND IN/OUT
switches
to
the
IN
position.
c)
Using the
same
procedure as in
the Signal Passage
Test above,
verify that
the gain
is the same
as
previously measured +0.3dB.
d)
Apply
a
20kHz
signal and adjust the output level
of
the
oscillator and the
622's
GAIN
control
until
+l8dBm
is observed at the 622 main
output.
e) Measure the Total
Harmonic
Distortion,
using the 400Hz
and
80kHz
filter
on
the distortion meter. The
THD
should not exceed 0.025%.
f) Repeat at 20Hz; +l8dBm
output;
400Hz
filter OUT. The THD
should not
exceed 0.025%.
4)
Noise
a) Adjust the
622 GAIN
control
to produce
unity
input/output gain.
b)
Switch OUT
the
400Hz and
80kHz
filters
in the analyzer.
Connect
the
20-20,000Hz
bandpass filter
between the
622
output
and the analyzer input.
c) Disconnect
the oscillator
from the
622,
and
connect
both
(+)
and
(-) 622
inputs
to circuit ground.
d) Center all
controls except
for
GAIN
(adjusted in
step
(a)), and place
all
IN/OUT
switches IN.
e)
Measure the
noise at the
main output
of the 622.
With
the
test setup
as
described, it
should
not exceed -84dBm.
If
only
the 80kHz
filter
internal to
the
analyzer
is available,
the
noise will
measure
somewhat
higher.
5)
HF,
MHF,
and
MLF
Equalizer Swept Response and Alignment
The
following
procedure
should be performed in
turn on
the
HF,
MHF,
and
MLF
bands. The
alignment procedure
for the
LF
band
is slightly
different and is
described
immediately
below. As
you perform the
tests, be sure that the
BAND
IN/OUT
switches of the
bands not
under test are OUT. If
the OVERLOAD
lamp
flashes at
any time, reduce the
GAIN.
14
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