Tektronix 5440 Instruction Manual page 61

R
ep laceme nt devices shoul
d
be of t he original type or a
direct re
p
laceme nt. Fig . 4-2 s hows the lea
d
co nfigurations
of t he semico n
d
uctor devices used in this instrument .
Some plastic-case transistors
h ave lead config u rations
that do
n
ot agree with
t hose s h ow n here. Wh e n replacing,
chec k the manufacturer's basing diagram for correct
basing . All transistor sockets in this instrume nt are wired
for th e stand ar
d
biasin g used for metal-case tran sistors.
Semiconductors t h at
h
ave heat ra d iators use silicone
grease to increase heat transfer.
R
e
p
lace the silicone
grease wh en replaci ng these semiconductors .
To re
p
lace one of th e
p
ower transistors mounte
d
on th e
ch assis ad j acent to the Power Supply circuit board, first
unsolder th e leads. Then , loosen
t
he nuts on th e plastic
bar, or the screw in the metal clamp, t h at clam p s the
transistor to t h e c hassis.
R
emove the
d
efective transistor .
Wh en re
p
lacing t he transistor, use silico ne grease on both
sides of th e insulator
p late and on the metal tab, if t h e
transistor
h as one, to increase heat transfer from th e
transistor to t he chassis .
Interconn ecti ng P in
R e
p
lacement . To re
p
lace α
p
in
whic h is mounte
d
on α circuit board , first discon nect any
p i n con nectors . Then, unsolder the damaged pin and pull
it out of the board with α p air of pliers .
B
e careful not to
damage the wiri ng on the boar
d
with too much h eat.
R
eam
out the h ole in the circuit board with α 0 .031-i nch drill .
R
emove the ferr ule from the new interco n necting
p
in and
p
ress the new
p
i n into the
h
ole in
t
he circuit boar
d
.
Position the pin
i
n
t he same ma nn er as t he ol
d p
in . If the
old pin was be nt at an an gle to mate with α connector,
ben d
t
h e new pin to matc h
t
he associate
d
pins .
Switches
Switch Replaceme nt. The followi ng main te nan ce infor-
mation is provided for the cam switches and pus h button
switch es used in
t
his instrument system .
M
ain tenance-5440
R
epai
r
of cam switc
h
es s
h
oul
d
be un
d
erta
k
en only
by experience
d
repair perso
n
nel. Switc
h
alignment
an
d
sp
r
ing tension of t
h
e contacts must be carefully
maintaine
d
for pro
p
er operation of t
h
e switc
h
.
F
or
assistance in
r
epai
r
of t
h
e cam switc
h
es, contact
you
r
local Tektronix Field Office o
r
representative .
An extraction tool should be used to remove th e 14-and
16-pin i n tegrated circuits to
p revent damage to the pins .
Th is tool is available from Te ktron ix, Inc. Order Te ktron ix
Α. CA M SW ITC HE S
Part No . 003-0619-00. If an extraction tool is not available
Two cam switc h repair
k
its are available, they are: Cam
when removing one of these integrate
d
circuits, pull
and evenly on both en ds of th e device . Try to avoid
Switch R
e
p
air
K
it, Te ktronix Part No . 040-0541-00; H ig h
slowly
h avi ng one en d of t he i n tegrated circuit
d
isen gage from
Frequency Cam Switc h Repair K it, Te ktronix Part No . 003-
the socket before th e ot her, as the pins may be
d
amage d
.
0708-00.
The first kit, Te ktronix Part No . 040-0541-00 is used to
re pair t h e cam switches i n most time-base plug-i n
u
n its
an
d
some vertical plug-in un its. The seco nd kit, Te k tronix
Part No . 003-0708-00 is
u
se
d
to re pair t h e cam switches
using the
h ig h -fre q uency co ntact, wh ic h is used
i
n several
vertical p lug-i n units.
The cam switches co nsist of α rotating drum with lobes,
w h ose
p
osition is controlled
b y t h e front-pa nel k nobs,
wh ic h actuate spri n g-leaf contacts .
T h e followi ng instructio ns have been ge neralized to fit
all instruments . Detailed instructions for cam switc h
repair, where require
d
, will be found in the app ropriate
manual .
1 .
R
emove any s hields, switch s h afts, i nterfering wires,
components, or circuit boar d
s wh ic h p reve nt access to the
circuit board with
t
he bad cam switch co ntact .
ΝΟΤΕ
Two ty
p
es of switch es are used i n
t
his instrument .
Cam switc
h
bearing bloc
k
s w
h
ic
h
attach to mo
r
e
Co ntact alig n me nt an
d
spacing are critical to the opera-
t
h
an o
n
e circuit boa
r
d s
h
oul
d
not be se
p
arated
f
r
om
tion of the pushb utton and cam switches . Therefore,
bot
h
boa
r
ds du
r
ing disassembly, unless absolutely
defective switch es shoul
d
either
b
e replace
d
as α u nit or
necessary, as proper bearing alig
n
me
n
t will be
re p aired only by person nel experienced with these ty pes
difficult.
of switc h es . Your local Te ktronix Fiel
d
Office or represen-
tative ca n provi de additional informatio n . The following
special mainte nance information is p rovi
d
e
d
for switc h
2 . Com
p
letely remove from the instrument th e circuit
replacement.
board havin g th e
d
efective cam switch co ntact .