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FRAGILE!
Even
so,
the
freight
people
will
throw
the
box
around
as
if
it
were
filled
with junk.
The
survival of
the
unit
depends
almost
solely
on
the care
taken
in
packingl
APPENDIX
A:
ALIGNMENT
INSTRUCTIONS
This section of the
manual
is
included primarily
for
purposes of reference, as
PERIODIC
COMPLETE ALIGN-
MENT
IS
NOT RECOMMENDED
OR
NECESSARY. Com-
plete
alignment
is
a step-by-step
procedure
which
assumes
that
none
of the
trimmer
controls
are correctly adjusted.
IF
THE REQUIRED
TEST
EQUIPMENT
IS
NOT
AVAILABLE,
DO NOT
ATTEMPT
TO
PERFORM
COMPLETE ALIGN-
MENT,,
Required
Instrumentation:
The
following instrumentation
is
required
for
complete
alignment:
(1)
Audio Sinewave
Generator,
with
less
than
0.05%
residual
harmonic
distortion
(2)
Digital
Voltmeter,
basic
DC
accuracy
0.1%
or better
(3)
Audio Voltmeter/Harmonic
Distortion
Meter
with
1
megohm
or
higher
input
impedance
(e.g.
H-P
334A)
(4)
Triggered
Sweep
Oscilloscope with
X-Y
capability
and
minimum
5
MHz
vertical
bandwidth
Setup
for
Complete Alignment:
Complete alignment
must
be performed on
a
test
bench
away
from strong
RF
fields.
Before
commencing
align-
ment, apply power and allow 30 minute
warmup
with
cov-
ers
in
place.
Remove
the top
and bottom
covers
imme-
diately before
starting
alignment procedure.
ALIGN-
MENT
MUST
BE
PERFORMED SEQUENTIALLY.
DO
NOT
SKIP STEPS. Alignment
points
can be found on
page
1 1
Alignment
Procedure:
(1)
Connect
digital
voltmeter
across
C605, and
read
voltage.
(2)
Adjust P601
for
a
reading
of
+15.00
volts
on
DVM.
(3)
Jumper
chassis
and
circuit
grounds together.
(4)
Turn P210 (broadband FET
bias)
CW
until
the
GAIN
REDUCTION
meter
indicates that gain reduction
is
beginning.
Back
off
P210
until
no
further
change
is
noted
in
GAIN
REDUCTION.
(5)
Adjust
P212
(G/R Meter
Cal)
until
the
GAIN
REDUC-
TION
meter
indicates
100%.
(6)
Connect
oscillator to
LEFT
AUDIO
INPUT.
Adjust
oscillator
for
5
kHz.
Adjust
INPUT
ATTEN
to
12
o'clock.
Increase oscillator output
until
GAIN REDUCTION
meter
indicates
-8.5
dB
(7)
Connect
oscilloscope
to
SCOPE OUTPUT
of distortion
analyzer.
Connect
input of distortion
analyzer
to the
left
channel
broadband
limiter
output (terminal 29),
which
is
a fork
terminal close
to the right rear
of the
limiter
board
when
viewed
from the
front.
Operate
distortion
analyzer
so that
the oscilloscope displays
the input
to
the
distortion
analyzer (normally
the
"SET
LEVEL"
mode).
Operate
the
scope
in
NORMAL
TRIGGER
mode, and
adjust trigger level so
scope
barely
stops triggering.
(8)
Remove
the hot lead of the oscillator
from LEFT
AUDIO
INPUT.
Turn the
RELEASE TIME
control
full
CCW.
Now
reconnect
the
hot lead of
the
oscillator,
trying
to
make
a
clean reconnect.
Observe
the scope,
which
should
trigger
on
the overshoot
produced by
the
finite
attack time of the
broadband
limiter.
With
the
scope
time base
set
at
2
ms/cm,
adjust
P210 (Broadband FET
bias)
trimmer
for
a
scope
pattern similar
to Fig.
2
This pattern will
be
transient, but
should
be
easily
visible.
Fig. 2
was photographed
using
a storage
scope.
To
repeat the pattern,
it
is
necessary
to alter-
nately disconnect
and
reconnect
the hot lead
of
the
oscil lator.
BROADBAND
LIMITER
ATTACK
(no signal
to 10
dB gain
reduction)
(2
mS/cm; IV/cm)
FIGURE
2
(9)
Reconnect
the
oscillator.
Switch frequency
to
1
kHz,
and reduce
the output
level until
4dB gain reduction
is
observed.
Without moving
the
distortion
analyzer
input,
measure
the
harmonic
distortion,
and
adjust
P203
(left
distortion
null) for
minimum
THD.
Typical
reading
will
be
0.025%
if
an 80
kHz
lowpass
filter
is
employed
to
reduce
the effects of
out-of-band
noise
on
the
reading
(10)
Connect
the oscillator
to
the
RIGHT
AUDIO
INPUT,
and
follow
the instructions
of
step 9, substituting
P204
(right
distortion null),
and
observing the
right
channel broadband
limiter
output
(terminal 31).
(11)
Connect
the
distortion
analyzer
to pin
^7
of
1C2
1
0b
Increase
oscillator
frequency
to
5
kHz; decrease
os-
cillator
output
until
GAIN
REDUCTION
meter
just
barely reads 0 dB.
Set the front-panel
TIME
CON-
STANT
switch to 75 uS.
8
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