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2:
MAINTENANCE
Preventive
Maintenance
AND
SERVICE
The
front panel
may
be cleaned with
a
mild household detergent. Stronger
solvents
should be
avoided, as they
may
damage
the
paint,
the silk-screened
lettering,
or
the
plastic
control knobs.
Corrective
Maintenance
All
Orban
products
are
designed
to
be
completely
free
of
failures
throughout
eternity.
However, Orban
research has recently discovered
that
there
is
no
justice
in
the world,
and,
in
fact,
there
is
not
supposed
to
be any.
For
this
reason,
the
following
Corrective
Maintenance
section
is
included.
CAUTION
Repairs
made
to
this
product should be
performed
in
accordance
with
applicable safety standards
for
your
country,
and
should
be
performed
only
by
a
well-qualified,
professionally-trained
service
technician.
Service
Access
Access
to
the
422A/424A
for
service
and adjustment
is
relatively
straightforward.
The 422A
contains only
one
card,
and
full
access
is
obtained
by removing
the top
and bottom
covers.
In
the
424A,
each
channel has
its
own
horizontally-mounted
circuit
card.
These
are
stacked,
so direct
access
to the
bottom
of
the
CHANNEL
A
board
or
the top
of
the
CHANNEL
B
board
requires a certain
amount
of
disassembly
beyond removing
the top
and bottom
covers.
However,
all
alignment trimmers can be accessed by
cover removal
alone, since
the
CHANNEL
B
alignment trimmers are
mounted
on
the bottom
of
the
CHANNEL
B
board,
whereas
the
CHANNEL
A
trimmers
are
mounted
on
the
tog
of
the
CHANNEL
A
board.
Full
access
to
one board
in
the
424A
requires
removal
.of
the other board. This
is
done
as follows:
1)
Knob
Removal:
Pry
the
plastic
cap
off
the
front of
each
knob.
Using
the
wrench
supplied
with
the
packing materials,
turn
the
now-exposed
collet
counterclockwise
until
the
knob
pulls
off
the pot shaft
easily.
(If
you have
lost
the
wrench,
a
screwdriver
will
probably work.)
2)
LED
Removal:
Grasping
the
leads,
gently
pull
each
LED
out of
its
plastic
lens.
3)
Meters:
Disconnect
the tab terminals
from each
of
the
two
meters, noting
which
tab goes
to
which
terminal
for later
reassembly.
4)
Board
Access:
Remove
eight
machine
screws from
the
edges
of
the board.
Slide
the board about
3/4"
(19mm) backward
to
assure
that
the pot shafts
clear the
front panel.
Then
tilt
the
board outward, imagining
a hinge at the
rear
edge.
5)
Complete
Board Removal:
If
you
want
to
entirely
remove
a
board,
the
various interconnections
must be
unsoldered.
27
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