REPAIR OF CONCEALED SHORT CIR-
CUITS IN PRINTED WIRING ASSEMBLIES.
Concealed short circuits in printed
If there is an eyelet or
wiring assemblies may be repaired by
plated-through hole not being
performing the following steps.
used for a component termina-
tion, it may be used as a
jumper wire termination.
Jumper wires shall be installed
If the end of any one of the
on the rear side of the assem-
jumper wires is to be attached to an
bly whenever possible, but if
etched conductor, plate the stripped end
necessary, jumper wires may be
of the wire on the conductor in a direc-
installed on the component side
tion parallel to the etched conductor
and solder in place. Then solder the
provided they do not cross over
ends of the other jumper wires in place.
the top of a component.
Encapsulate each of the jumper
wires as described in steps 7 thru 10.
The repair of concealed short
circuits involves three steps:
(1) isolation of the shorted
area, (2) cutting the conduc-
tors at each side of the short,
Use Freon with good ventila
tion. Avoid prolonged or
and (3) restoring the continu-
repeated breathing of vapor.
ity by the installation of
Avoid contact with skin and
eyes. Do not take internally.
1. Technical personnel familiar with
7. Clean the areas to be encapsulated
the function of the circuit must deter-
using Freon TMC solvent. Be sure that
mine the area of the short circuit, the
all traces of rosin flux are removed.
conductors to be cut, and the jumper
wires to be installed.
1/8 inch long in each shorted conductor
Adhesives are irritating to the
on each side of the short.
skin and eyes upon contact, and
may emit harmful vapor. Use
Form 26-gage insulated copper
only with adequate ventilation.
jumper wires between the designated
Avoid all skin and eye contact.
points on each side of the short circuit
Use protective clothing such as
rubber gloves, apron and eye
protection. Wash off immedi-
Strip the ends of each jumper wire
ately any accidentally contami-
a distance of 1/4 to 5/16 inch.
nated skin areas. Hand washing
facilities and eye washing
fountain should be provided.
Do not take internally.
The areas to be soldered must
Use any one of the Narmco Epoxy
flows. Overheating can damage
Adhesive Kits No. 3135 listed in
the board or nearby components.