Servicing Printed Wiring Boards - HP BENCH Series Operating And Service Manual

Excessive heat or pressure can lift the copper strip from the board. Avoid damage by using a
low power soldering iron (50 watts maximum) and following these instructions. Copper that lifts
off the board should be cemented in place with a quick drying acetate base cement having good
electrical insulating properties.
A break in the copper should be repaired by soldering a short length of tinned copper wire
across the break.
Use only high quality rosin core solder when repairing etched circuit boards. NEVER USE
PASTE FLUX. After soldering, clean off any excess flux and coat the repaired area with a
high quality electrical varnish or lacquer.
When replacing components with multiple mounting pins suchastube sockets, electrolytic capa
citors, and potentiometers, it will be necessary to lift each pin slightly, working around the
components several times until it is free.
WARNING: If the specific instructions outlined in the steps below regarding etched circuit boards
without eyelets are not followed, extensive damage to the etched circuit board will result.
1. Apply heat sparingly to lead of component
to be replaced. If lead of component passes
through an eyelet
in the circuit
board, apply
heat on com
ponent side
of board. If
lead of com
ponent does
t^pass through an
eyelet, apply heat to conductor side of board.
2. Reheat solder in vacant eyeletand quickly
insert a small awl to clean inside of hole.
If hole does
not have an
eyelet, in
sert awl or
a #57 drill
from con
ductor side
of board.
CONDUCTOR
SIDE
3. Bend clean tinned lead on new part and
carefully insert —
through eyelets or
holes in board.
4. Hold part against board (avoid ove rheating)
and solder leads.
Apply heat to compo
nent leads on correct
side of board
as explained tai
in step 1.
In the eventthat eitherthe circuit boardhas been damaged orthe conventional method is imprac
tical, use method shown below. This is especially applicable for circuit boards without eyelets.
1. Clip lead as shown below.
2. Bend protruding leads upward
-CLIP
HERE
. Bend lead
of new APPLY
component SOLDER \ \
around pro- TJiiifi fl
truding lead.
Apply solder ^
using a pair 1
of long nose pliers as a heat sink.
This procedure is used in the field only as an alternate means of repair. It is not used within
the factory.
I
Figure 5-11. Servicing Printed Wiring Boards
5-12