Orban 424A - Page 33

Replacement Parts: If you
have difficulty
finding parts for
this or
any other
Orban
product, Orban Customer Service stands ready
to supply you with the
required
parts at
a
fair price. Please call us at the telephone
number shown at
the
front of this Manual.
Replacement of
Components on Printed Circuit Boards
It
is
important to use
the correct technique
for
replacing
components
mounted on
PC boards. Failure
to do
so
will result in possible circuit damage and/or
intermittent
problems.
The circuit
boards
used in the 424A are of
the
double-sided plated-through variety.
This
means that
there are
traces
on both sides
of
the board,
and that
the through-
holes contain a
metallic plating in order to conduct current through the board.
Because of
fhe plated-through holes, solder often creeps 1/16"
up
into
the hole,
requiring a
sophisticated
technique
of component removal to prevent serious damage
to
the board.
Removal: If
the
technician
has
no practical
experience with
the
elegant and
demanding
technique
of
removing
componenfs from double-sided
PC
boards wifhouf
board damage,
if is wiser
to
cut each of
the
leads of
an offending componenf from
its body
while the leads are still soldered into the board. The component is
then
discarded, and each lead is heated
independently
and pulled out of the
board with
long
nose
pliers. Each hole may
then
be cleared of solder by carefully heating
with
a
low-wattage
soldering iron
and sucking
out
the
remaining solder with a
spring-
activated desoldering tool. THIS METHOD IS THE
ONLY
SATISFACTORY
METHOD
OF
CLEARING
A
PLATED-THROUGH HOLE
OF
SOLDER!
Another
technique
is:
1)
Use a
30
watt
soldering
iron to
melt
the solder
on
the
solder
(underneath)
side
of
fhe PC board. Do
not
use
a
soldering gun or a
high-wattage
iron!
As
soon
as
the
solder is
molten, vacuum it away
with
a
spring-actuated
desoldering tool like
the
Edsyn
"Soldapullt". AVOID
OVERHEATING THE
BOARD;
overheating will almost surely damage the board
by
causing
the
conductive
foil
to separate from
fhe
board. Use a pair
of fine needle-nose
pliers fo wiggle
the
lead horizontally
until it can
be observed
to
move
freely
in the
hole.
2)
Repeat step (I) until each
lead
to
be removed has
been cleared of solder
and
freed.
3)
Now
lift the component
out.
Installation:
1)
Bend
the
leads
of
fhe
replacement
component until it will fit easily into the
appropriate
PC
board
holes.
Using a good brand of rosin-core
solder,
solder
each
lead
to
the
bottom side
of the board with
a 30
watt
soldering
iron.
Make
sure
that the
joint is smooth
and
shiny. If
no damage has been
done to
the
plated-through
hole, soldering of the
topside pad is not necessary.
However, if the
removal
procedure did not
progress smoothly,
it would
be
prudent to
solder each
lead at
the
topside
as
well in order to
avoid potential
intermittent
problems.
2)
Cut
each lead of fhe replacement
component
close to
the
solder
(underneath)
side
of the PC board
with a pair
of diagonal cutters.
29