Orban 424A - Page 31

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