dbx 363X - Test Procedures; Power Supply Testing

AKG
Acoustics
Inc.
dbx
Model
363X Test
Procedure
Revision
03
-
10/9/90
Note:
The
following
steps
need not
necessarily
be
performed in
the
exact
order
or manner described.
However,
AKG
Engineering
must be consulted
before making
any such
changes.
A. Power supply
1.
Plug
the
transformer
into
an
outlet with
120
VAC.
2.
Monitor
TP2 and
verify
+24 volts
DC
+/-
3
volts with less than
0.5
volts
peak-to-peak
ripple.
3.
Monitor
TP3
and
verify
-24
volts
DC
+/-
3
volts
with
less
than 0.5
volts peak-to-peak
ripple.
4. Monitor TP4
and verify
+
12
volts
DC
+/-
0.6
volts.
5.
Monitor
TPS and
verify
-12
volts
DC
+/-
0.6
volts.
B. RMS
Symmetry
1.
Set all front
panel
switches
to
the
OUT
position.
2.
Connect a
50
Hz sine
wave
at
1
volt
rms to
Channel
1
input (rear
panel).
3.
Monitor
TP16
and
adjust
R19 for a
symmetrical
100
Hz sine
wave
aproximately
350
mV
peak-to-peak.
This
is the same as adjusting
for
minimum
content
at
50
Hz.
4.
Repeat for
Channel
2 using
TP
17
and
R76.
C. VCA
Symmetry
—
1. Set all front
panel
switches
to
the
OUT
position.
2.
Connect a tone-burst
oscillator
to the
Channel
1 KEY INPUT and
press
the
Channel
1 KEY
ENGAGE
button.
The
frequency
of
the
tone
should
be
about
1
kHz.
The
ON level should
be approximately
1
volt
rms and
the
OFF level should
be
less than
100
mV.
The repetition
rate
should
be
4
per second or
high
enough
to
produce
easily
viewed
traces
on
an
oscilloscope.
Any
combination
of
levels
and
repetition
rate
that
opens
and
closes the gate
will
work.
3.
Set
the
Channel
1
HOLD
and
RELEASE
controls to the
full
counter-clockwise
positon
(
HOLD
to
“OFF*
and
RELEASE
to
*3k"
).
4.
Adjust the
Channel
1 THRESHOLD
knob until the
green
OPEN
LED,
yellow
HOLD
LED
and
red
RELEASE
LED are
flashing on and
off.
5.
Monitor
the
Channel
1
output
and
adjust
R5
for
minimum
AC
waveform.
6.
Repeat
for
Channel
2
using
R62.
D.
VCA
gain
1. Set all
front
panel
switches
to the
OUT
position.
2.
Apply
a 1 kHz
sine
wave at
1 volt
rms
+/-
to
the Channel
1
input.
3.
Adjust
the
Channel
1
THRESHOLD
knob so
that
the green
OPEN
LED