BWD MINI-LAB 603B Manual page 58

8
.
MAINTENANCE:
(continued)
8.5 Removal
of
Components
from Printed Circuit Boards;
(cont'd.)
Before attempting a
repair
determine,
if
possible, the faulty
component
and remove
only
that
component.
(Be sure the trouble
cannot be cured by an
adjustment).
Turn
off
power before attempting removal.
The
first
step
is
to
clip the leads
near
the
component, and remove
the
component.
Then apply
the soldering iron
tip to
the
conductor
side of the
board at the
component
lead which
is
then
removed with a
straight
upward
motion.
For large
components
with
the leads rigidly
connected,
i.e.
preset potentiometers, the
soldering
iron tip
should be
rotated
from lead
to
lead
while applying
pressure
to
the
component
to
lift it
from
the circuit
board.
8.6
Repair
of Printed Circuit Boards;
Generally
when
replacing
components on a
circuit
board two
types of
damage
can
take place
a.
A
conductor
strip
can
lift
from the
board.
b.
A
conductor
strip
may
break.
A
lifted strip
may
be re-cemented with a quick
drying acetate
cement
having
good
electrical insulation characteristics.
A
broken conductor
strip
may
be
joined
by a
short length
of
tinned copper wire.
DO NOT
attempt
to bridge a
break with
solder.
8
.
7
Removal
of Front Panel Controls:
This
Section
describes the removal
of
all
front
panel
rotary controls
except
the
frequency
vernier;-
a. The knob
may
be removed by
loosening the grub screw(s)
in the side.
There are
two
types of
grub
screws,
one
requiring a
3/64" AF
hexagonal
key and
the other requiring a
5/64"
AF
hexagonal key.
b.
The
wires soldered
to
the control should
now
be
unsoldered
after
making a
note of their connection.
c.
Using a 1/2" AF
ring or
tube spanner,
remove
the nut holding the control
to the front panel,
d.
The
control
may now
be withdrawn from
the panel.
e.
Assembly
is
done
in
the reverse order.
8-2
603B