Orban 424A - Page 32

In
the 424A,
power
is supplied from the
CHANNEL A
board
to the
CHANNEL
B
board through a plug which
is
simply
pulled
off. In addition, the
two boards are interconnected by means of
wire leads connected to the
COUPLED/INDEP switch. The
two wires may be unsoldered
at
the
COUPLED/INDEP switch, noting which
wire goes
to
which terminal.
(This
switch is soldered
to
floating
pads
on
the
board
to secure
it mechanically.
However,
it does
not
connect
to
any printed
wiring.)
Reassembly is
performed in the reverse of disassembly.
(If
notations
as
to which
wire goes to
which terminal are misplaced, consult
the
schematic
at
the back
of
this manual
to deduce the
correct wiring.)
Circuit
boards should be
fastened using
eight screws removed above, taking care
to center
the switch shafts in their holes to avoid binding.
When the
knobs are reattached, they should first
be
partially tightened, leaving a
small clearance
between
the
knob and
the panel. Once partially tightened, each
knob should be turned so that it aligns with
the
markings
on the
panel
at
the
counterclockwise stop
of
the pot.
Once
properly aligned, each knob should be
firmly tightened.
Then replace the
snap-on
caps,
accurately aligning the
marking
on the cap to the marking
on the
knob.
The meters
should be reconnected
as
necessary, and the
LED's
reinserted in
their
color-coded lenses.
Operation of
the
unit should be checked before the covers
are installed.
Lamp
Replacement:
Lamps supplied
with
the 422A/424A
are
a
long-life
type
which
are
operated
below their rated voltage. They are not
expected to fail in
the
field
under normal
circumstances. If they do fail, replacement requires
removing
the
meter bracket after removing one circuit
board. The correct replacement
is
a
#1847 lamp;
a #47
lamp
may
be substituted in an emergency, although its life
is
shorter and
it
may therefore require inconvenient future
replacement. (If
one lamp
is replaced,
it
may be advisable to replace the other to avoid future work.)
Component Replacement:
All IC's in
the
unit are socketed and can be
readily
replaced from the top
surface of each board. Realignment
is
required if
IC5, IC6,
IC7, IC8, or ICO is replaced.
Other components
are soldered
in
place,
and
may be replaced following
the
instructions
in Replacement of
Components On Printed Circuit
Boards
immediately
below.
The
two potted
modules on each board
are
not
field-repairable, and
must be
replaced
in their entirety.
While either module can
be replaced
without realignment
of
the
unit,
diagnosing failures
in the Compressor/Limiter Timing Module can be
tricky and is best left
to
the factory
unless you are willing to risk the
expense of
replacing a
possibly good module!
If
filter
capacitors are
to
be
replaced, fasten
them
securely
to the
board, using
the original factory installation
as
a model. This will
prevent their breaking
loose
in the future from vibration.
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