Tektronix 576 - Page 78

M ai n tena n ce-Type 576
R otary Switch es . Individual wafe r s or mec h anical
p
arts
of rotary switc h es are normally not re p laceable .
If
α
switc h
is defective, replace t h e enti r e assembly . R
e p
lacement
switc h es can be ordere d eit h er wire d or unwired ;
refer
to
t he E lectrical Parts L ist for t h e a pp lica b le p art number .
Wh
en replacing α switc
h ,
tag t
he
lea
d s
and
switc h termi-
nals wit h co r res p onding identification tags as t h e lea d s are
disco n necte d . T hen , use t he ol d switc h as α gui de for
installing t he n ew one .
An
alternative met h o d is to draw α
s k etc h of t h e switc h layout and recor d t he wire color at
eac h terminal . Wh en soldering to t he new switc h , be careful
t
h at the solder does not
flow
beyon d t he rivets of t he
switc h termi n als . Sp r ing tension of t he switc h contact can
be d est r oyed by excessive sol d er .
Semicon du ctor R ep lacement . Semicon d uctors s h oul d
not be re p laced un less t hey are actually defective . If re-
moved from t h eir soc k ets during routi ne main tenance,
ret u rn t h em to th ei r o r iginal sock ets . U nnecessary re p lace-
ment or exc han ge of semicon d uctors may affect t he calibra-
tion of
t
h is
i nstrument
. Wh en semicon d uctors are re p laced,
c h ec
k
t he op eration of t h at part of t h e instrume nt w h ich
may b e affecte d .
PO WER switc h must be tu r ne d off before removing
o r re p laci n g transistors .
R ep lacement semicon d uctors sh oul d be of t he o r iginal
type or α d irect
replacement
.
F ig . 4-2 s h ows t he lea d con-
figuration of t h
e semicon
d uctors use d
in
t
h
is
instrument .
Some plastic case transistors h
ave
lea d
configuratio n s w h ic h
do not agree wit h
t
h ose
sh
own
h ere . If α semicon
d
u ctor is
replace d by one w
h
ic h is ma d
e
by α d
iffe r ent man
u
factu
r
er
t h an t h
e
original,
c
h
ec
k t h
e manufacturer's
basing d iagram
for correct basing . All transistor soc k
ets
in t
h
is
i
n str
u ment
are wire d fo r t h
e
basing use d for
metal-case
transistors .
U
se
silicone grease w h en re p lacing transistors w h ic h h ave heat
ra d iators . U se silico ne grease w h en re p lacing transistors
w h ic h h ave heat ra d iators or a r e mounte d on t he ch assis .
R eplace t he silicone grease w he n r ep lacing t h ese transistors .
Han dle silicone g r ease with care . Avoi d getting
sili-
cone grease i n t he eyes . W as h
h
a n ds
t h
oroug
h
ly
after
use .
R
elay R
ep
laceme
n t . R elays li ke t he one on t he Step
Generator circuit board (Te k tro
n
ix
P art
Νο .
148-0044-00)
may be turned eit h er directio n w hen connected to t he cir-
cuit board .
F
use
Re p lacement . T h e power-line f u ses are locate d on
t he r ear p anel in t he V oltage Selector Assembly . See t h e
electrical p arts list for t he values of t he fuses .
Graticule L
am
p
R
eplacement . T he gratic u le and rea dout
title lamps may b e remove d from t he r ear of t he graticule
lamp circuit boar d by lifting t he retainers from t he con tact
of the lamp and pulling t he lamp out from t he rear .
4- 1 2
CA U TIO N
W
A
RN
I N G
R eadout L am p
Replacement . U
se
t he following pro-
ce d
ure
to re p
lace α rea dout lamp :
1 . R emove t h e
bezel
f r om
t
h e Ty p e 576
front- p anel .
2 . Pull t he rea d
out
assem
b
ly
from
t
he i n
strume
n
t .
3 . Remove t
he metal cover from t h e r ea d out assembly
w
h ic h h
as
α bu
rn
e do u t lamp .
CA U TIO N
Do
n ot
loosen or remove h
eat
si nk
s o
r rea
dou t sh elves
w
h en re p lacing
r
eadout
lam
ps .
4 . If t he lam p to be re p lace d is connected to one of t h e
rear rea d o u t lam p circuit board s, disconnect the readou t
logic circuit board from t he rea dout assembly .
5 . U nsol d er the lamp lea d s of t h e burned out lamp from
t he bac k of t he reado u t lamp circuit board . To d etermine
w h ic h lea d s to unsol d er, locate t hep i n on
t h
e rea
d
out
logic
circuit board w h ic h pertains to
t he
bur
n ed
out
lam p , and
follow t he color-co
d
ed
wire from th at p in to t he rea dout
lam
p
circ
u
it board
.
6 . Pull
t he rea dou t lam p circuit board (an d blac k p lastic
mo
un ting) far eno u g h
away
from its h ol de r to replace the
damaged lamp and replace t he circuit board .
7 . Sol d er t he new lamp lea d s to t he readout lam p circuit
board .
8 . R eplace t
he rea dout lamp assembly cover (an d rea d -
out logic circuit
boar d if r emove d ) .
Ceramic
Te
r
minal
Stri p
R
ep
laceme
n
t . Α
com p
lete
ceramic termi n al stri p assembly is s h own i n
F
ig . 4-4
.
Re p lacement stri p s (i n cl ud ing st ud s) a nd s p acers are
su pp lie d un d er separate p art numbers . H owever, t h e ol d
s p
acers
may be re-use d if t
hey
are not damage d . T h e app lic-
able Te k tornix Part Nu mbers for t he ceramic st r i p s and
s p acers use d in t h is i
n
str u ment are given in t he Mechanical
Part L ist .
N otc h
III ι .
ywwwwv , ωωωωω y ~ ; ι , W ωωωωω
C h assis S
p
ace r St
ud Pin
St ud
F ig .
4-4
. Cera mic terminal stri p assemb l y .