Tektronix 7B10 Instruction Manual page 41

Maintenance --7B10
The
reliability
and
accuracy
of this
instrument
can be
maintained only
if
proper soldering techniques are used
when
repairing or
replacing
parts.
General
soldering
techniques,
which
apply
to
maintenance
of
any
precision
electronic
equipment, should be used
when
working
on
this
instrument.
Use
only
60/40
rosin-core, electronic-
grade
solder.
The
choice
of
soldering
iron
is
determined
by the repair
to
be made.
When
soldering
on
circuit
boards, use a 15-
to
40-watt
pencil-type soldering iron with
a
1
/8-inch wide,
wedge-shaped
tip.
Keep
the
tip
properly
tinned
for
best
heat transfer
to
the solder
joint.
A
higher
wattage
soldering
iron
may
separate the wiring from
the
base
material.
Avoid excessive heat; apply only
enough
heat
to
remove
the
component
or
to
make
a
good
solder
joint.
Also,
apply only
enough
solder
to
make
a firm solder
joint:
do not apply too
much
solder.
>
CAUTION
^
y- y- .y y-
y-
y
y- ^
All
circuit
boards, except the readout
circuit
board,
in this
instrument are multilayer type
boards with a conductive
path(s)
laminated
between
the top
and
bottom board
layer.
AH
soldering
on these boards should be
done
with
extreme
care
to
prevent breaking the
connections
to
the center
conductor(s):
only
experienced
maintenance personnel should
attempt repair of
these
boards.
For
metal terminals
(e
g.,
switch terminals,
potentiometers,
etc.),
a
higher wattage-rating soldering
iron
may
be required.
Match
the soldering iron to
the
work
being done.
For example,
if
the
component
is
connected
to
the chassis
or
other large heat-radiating
surface,
it
will
require a
75-watt or larger soldering
iron.
The
following
techniques should be used
to
replace a
component on
a circuit
board:
1.
Grip the
component
lead
with long-nose
pliers.
Touch
the soldering iron to
the lead
at
the solder connection.
Do
not lay
the
iron directly
on
the board, as
it
may damage
the board.
2.
When
the solder
begins
to
melt,
gently
pull
the lead
out.
If
unable
to pull
out the
lead
without using
force, try
removing the other
end
of
the
component
as
it
may
be
more
easily
removed.
NOTE
Some
component
leads are
difficult to
remove
due
to
a
bend placed on each
lead during the
manufacturing process
The bent
leads
hold
components
in
place during
a
process
that
solders
many
components
at
one
time.
If
a
component
lead
is
extremely
difficult to
remove,
it
may
be
helpful to
straighten the leads on the back
side
of
the
board with
a
small
screwdriver
or
pliers
while
heating the soldered connection.
Use
only
enough
heat
to
remove
the
component
lead
without removing
the solder
from the board.
If it
is
desired
to
remove
solder
from
a circuit-board hole
for
easier installation
of
a
new
component,
a solder-
removing wick
or solder extractor
should be
used.
3.
Bend
the leads of the
new
component
to
fit
the holes
in
the board.
If
the
component
is
replaced while the
board
is
mounted
in
the instrument, cut the leads so they
will just
protrude through the board.
Insert
the leads
into
the holes so the
component
is
firmly seated against the
board
(or
as positioned
originally).
If
if
does
not seat
properly,
heat the solder
and gently press the
component
into place.
4 Touch
the iron to the
connection
and
apply a small
amount
of
solder
to
make
a firm solder
joint.
To
protect
heat-sensitive
components, hold the lead
between
the
component body and the
solder
joint
with
a pair of long-
nose
pliers or
other heat
sink.
5.
Clip
any excess
lead
protruding
through
the
board
(if
not clipped
in
step
3).
6 Clean the area
around
the solder
connection with
a
flux-removing
solvent.
Be
careful not to
remove
information printed
on
the board.
COMPONENT REMOVAL AND
REPLACEMENT
WARNING
I
To avoid
electrical
shock,
disconnect the
instrument from the
power source
before
replacing
components.
The exploded-view drawing associated with the
Replaceable Mechanical
Parts
list
may
be helpful
in
the
removal
or
disassembly
of
individual
components
or
subassemblies.
Component
locations
and
circuit
board
locations are
shown
in
the
Diagrams
section.
CIRCUIT
BOARDS
If
a circuit
board
is
damaged
beyond
repair,
replace the
entire
board assembly.
Part
numbers
for
completely
wired boards are given
in
the
Replaceable
Electrical Parts
list.
4-8