STAR*TEcH
July 1996
Journal
... continued from previous page
from the main crack or break
need attention.
trical circuit paths. Of course,
some repair techniques do both
at once.
We do this the same way we stop
a crack in an auto windshield.
Follow each crack to
where it ends and drill
.
.
a small hole there. This
JU rnrer WI re
strain relief hole will
a:::ross m rner
prevent the crack from
going any further. Hon-
est.
tra::e
PC ooard
m rner bro ken off
From time to time I find I can't
repair something so that all the
parts remain where they started.
In these cases I can find an un-
used area nearby on the PC
board, drill a couple small holes,
and mount the part in a new spot
with wire jumpers back to the old
neighborhood.
Sometimes I even make a small
auxiliary circuit board to hold a
few components. This I can
mount with sticky foam or some-
thing. (I keep a collection of hob-
byist/ experimenter PC boards
from Radio Shack for the pur-
pose.) It is easy enough to cut a
home made board to size with a
fine saw like those X-acto makes
or even a hacksaw. I use a Dremel
tool.
REPAIR TuCHNIQ,UES
Cracks need to be stopped. Even
little ones that shoot off away
Naturally you want to
avoid drilling through
components on the
other side of the board.
If necessary, tempo-
rarily remove the of-
fending component.
Make sure your relief hole
doesn't slice a circuit trace in two.
Sometimes shining a bright light
through the board makes cracks
easier to see.
I use a Wahl cordless soldering
iron with the PC drill attachment.
We need to restore the electrical
paths, but we might as well do
double duty and make the elec-
trical repairs part of the structural
repairs, as much as possible any-
way.
Solder is used as a bonding agent
and as an electrical conductor,
but it doesn't have a lot of
strength. Try bending a piece
back and forth in your hands, and
you will find it breaks fairly
quickly. If you just bridge a crack
with a blob of solder, it will break
for the same reason.
Use wire to cross the gaps and
cracks. I save the inch long leads
I trim off caps and resistors when
I install them. I keep a supply in
a little jar next to my soldering
iron for this purpose. Otherwise,
get a roll of solid conductor wire.
To lay down a patch, we must first
prepare the surface. Remove the
conformal coating, that green
twist up t: ight:
to pu 11 cra:::k. to0% her
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• bai Ii ng wire• repair
I find it real handy, but any drill
will do. Use a small bit. I keep a
=#=56 drill bit in my PC drill. That
is a lot smaller than a 1/16". If
your hardware store doesn't stock
small number size drill bits, try a
hobby store. They're cheap.
stuff, to expose the bare copper
trace. Nothing works better than
the fiberglass brush eraser (and
don't get the fibers get in your
skin) but you can also scrape the
coating off with a razor blade or
X-acto. There are solvents, but I
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