Tektronix 2213 - Page 97

M aintenance-2213 Service
SO
L D ER I N
G
T E
C
HN IQ UE S
The r eliability an d accuracy of this instrument can
b
e
maintaine d only if
proper soldering techniques are
used to
remove or replace parts . General sol d ering
techniques, which apply to maintenance of any p recision
electronic equipment, should be u sed when working on this
instrument .
W A RN I N G
To avoid an elect r ic-s hoc k h aza r d, observe t h e follow-
ing p r ecautions before attem
p ting
a
n y sol d er i ng :
turn t
h
e i n strument
off,
disconnect
it from t he ac
powe
r
so
u rce, a n d
allow
a ppr oximately t h ree min u tes
fo
r
t
h e powe r -su p ply capacitors to d isc h arge .
U se r osin-core wire solder containing 63% tin and 37%
lead . Contact your local Tektronix F iel d Office or repre-
sentative to obtain the names of approve d solder types .
When soldering on circuit b oards or small insulate d
wires, use only α 15-watt, p encil-type sol d ering iron . Α
h igher wattage soldering iron can cause etched circuit
conductors to separate from the board b ase material and
melt the insulation on small wires . Always keep t he
soldering-iron tip p ro p erly tinned to ensure best h eat trans-
fer from the iron tip to the solder joint . To protect
h
eat-
sensitive components, either
h
old t
he com ponent lead with
long-nose p liers or place α h eat b lock
between
t he com-
ponent b od y and t he solder joint . Apply only enough
solder to make α firm j oint . After soldering, clean t he area
around the solder connection with an ap p rove d flux-
removing solvent (such as isopro p yl alcohol) and allow it to
air d ry .
Attempts to un sol d e r , remove, a nd resolde
r
lea d s
fr om t h e compone n t si de of α circ u it boa rd may
ca
u
se
damage to t he reverse si de of t h e circ u it b oard .
The following techniques shoul d be use d to r eplace α
component on any of the circuit b oards :
1 .
Touch t he vacuum d esol d ering tool to the lead at
the solder
connection . N ever p lace the iron d irectly on the
b oar d ; d oing this may d
amage the b oard .
ΝΟΤΕ
Some com p o n e n ts a re d iffic u lt to remove from t he
ci r c u it board du e to α bendp lace d in eac h lead d uring
mac h i n e insertion of t h e component . T h e p u r p ose of
t
h
e be n t
lea d
s
is
to
h ol d
t
h e component in place
dur i ng α solder-flow man u fact u ring p r ocess t h at
solders
all
t h e com p onen ts at once . To ma k e removal
of mac h ine-inserte d com p onents easie r , st r aig h te n
t he com p onent leads on t
h
e reverse si d e of t he circuit
board wit
hα small screw d rive r o r pliers
It may be
necessary to
r emove t he circuit boa r d to gai n access
to
t
h e compone n t leads
on
t h e reverse si d e of t h e
ci r c u it b oa r d . Circ uit-board removal and r einstallatio n
proce d u r es are disc u ssed later in t h is section .
2 . When removing α multipin component, especially an
IC, d o n ot h eat adjacent pins consecutively . Apply h eat to
pins at alternate sides and ends of the IC as sol d er is
removed . Allow α moment for the circuit b oard to cool
before p roceeding to
the
next p
in .
E xcessive h eat ca n ca u se t h e etche d cir cuit con-
ductors to se p arate fr om t h e circ
u
it boa rd . N
eve
r
allow t h e solder extractor tip to remai n at one p lace
on t h e boa rd for more t han t h ree secon d s . Solder
wic k , sp r i n g-act u ated or s q ueeze-b u lb solder s u c k ers,
and heat bloc k s (fo
r
d esoldering multi
p
in com-
p one n ts) m
u
st not be
u
sed . Damage ca
u
se d bypoor
sol d er i ng tech niq u es ca n voi d t he i n st r ument
warranty .
3 . To replace the com p onent, b end t he leads of the
r eplacement item to
fit the h
oles
in
t
he circuit board . If the
com
p
onent
is r
eplace d while the b
oar
d
is
installed i n t he
instrument, cut the leads so they p rotrude only α s mall
amount through t he reverse side of the circuit board .
E xcess lea d length may cause shorting to other conductive
p arts .
4 . Insert the leads into the h oles of the board so that
the replacement component is p ositioned t he same as the
original component . M ost components should be
firmly
seated against the circuit b oard .
5 . Touch t he soldering iron to the connection and apply
enough solder to make α firm solder j oint . Do not move the
component while the solder har dens .
6 . Cut off any excess lead p
rotruding through t he circuit
b oard (if not clip ped to size in step 3) .