Tektronix 576 Manual page 71

2. Check Instrument Calibration.
C
hec k the calibration
of th is instrument or of the affecte
d
circ uit if the trouble is
k nown to exist in one
p
articu lar circuit. The apparent
trouble may be only α result of misa dj ustment an d may be
corrected by calibration . Com p lete calib r ation instructions
are given in the
P
erformance C hec k and Calibratio n section
of th is manual .
3 .
L
ocating
M
alfunctio ning Ci rcuits. To locate the
source of α malfunction in inst rument operation, the
trouble symptom will often indicate the identity of the
fa ulty circuit(s) . For exam p le, if α d isplay of the Collector
Su pp ly output ca n be obtain e d on th e test oscillosco p e
C RT but α
d isplay of the Ste p Generato r output cannot b
e
obtained , the Ste p Generator is probably malfunctioning .
If the trouble symptom
d
oes
n
ot i n dicate wh ic h cir-
cuits) is causing
p
roblems (for exam ple if there we re no
Collector Su pply or Step Generator outputs), α more sys-
tematic trou bleshooting proced ure is necessary . Fig . 4-3
p
rovi des α ge neral gu ide for locating the probable ci rcuits
wh ic h are causing the instrume nt to malf unction .
The following
p
reliminary procedure ensu r es t hat t he
instrument malfunction is not caused by im pro per control
settings and h elps
d
etermi ne w here to begi n on the trouble-
sh ooti ng chart:
Α . Set the following Ty pe
G RATIC ULE
I
LLUM
RE ADO UTI LLUM
I
N TEN SITY
FOC US
VERTICA L
DISPL AY O FF S ET Selector
C EN TERL I NE VALUE
HO R IZONTA L
P OSITIO N (Vert an d
H
or iz)
F I NE P OSITIO N ( Vert an d H
oriz)
Z ER O
CA L
DIS PLAY I NVER T
MAX PEAK V O LTS
PEAK
P
OWER WATTS
VAR IA BLE CO LLECTO R
S
UPPLY
POLARITY
M OD E
LOO PI NG CO MPEN SATIO N
NUMBER O F ST EPS
C URRENT
L
I M IT
AMPLIT U DE
O FF SET
O FF SET MULT
ST EP S
PULSE D ST EP S
ST EP FAM I LY
R
AT E
PO LA R ITY I NVER T
ST EP MULT .1 Χ
576 controls to :
F ully Cloc kwise
F ully Cloc kwise
Trace V isible
Centered
1 mA
N
O RM (O FF)
0
2 V CO LLECTO R
Centere d
Ce ntered
R
eleased
R
eleased
R
eleased
15
0 .5
Fully Cloc kwise
+( ΝΡΝ )
N
ORM
As Is
10
20 mA
2 V
ZER O
0
P
ressed
R
elease d
REP
N O RM
Released
R
eleased
M
aintenance-Ty
p e 576
Terminal Selector
BAS E
T
ERM ST EP
G
EN (N ORM)
LEFT-OFF-R IG HT
R
IG HT
Β . Turn on the Ty pe 576 an d allow α few minutes to
warm
up .
C . C HE C K FO R -Dis play of Collector Su pply sweep of
about 15 volts pea k on Ty p e 576 CR T.
D . If no display can be obtained, connect the 10 Χ
probe between the test oscilloscope an d
t
he collecto r te rm-
inal on the right han d side of the Standard Test F ixture
(connect grou nd lead to emitter terminal) .
Ε .
C
HE C K FO R -Display of Collector Su pp ly output is
α
p
ositive-going fu ll-wave rectified sine wave of about 15
volts
p
ea k on test oscillosco pe CRT.
F. Connect the
p
robe to the right base terminal of the
Stan dar d Test F ixtu r e.
G . C HE C K FO R -Dis play of Step Generato r output of
p
ositive-going steps of 2 volts/step on test oscilloscope
C RT.
Η . Start with
t
h e following step on F ig . 4-3 according to
the
r
esu lts of the
p
revious chec ks:
1 . Step (A)-No Collector Su pply output ; Step Ge n-
erator output or d is play on the Ty pe 576 C R T.
2 . Step (B)-No Collector Su pp ly output or incorrect
outpu t, bu t Step Generator is dis played and
t
he spot can
be seen on the Ty pe 576 C RT.
3. Step (C)- Νο Step Generator output (or incorrect
out put), but Collecto r
S
upp ly is displaye d on the Ty pe
576 CR T.
4. Step (D)- Νο d isp lay on type 576 C RT (or incor-
rect
d
isp lay), but Collecto r Su pply outp ut and Ste p Gen-
erator output are
d
isplayed properly on the test oscillo-
scope C RT.
After the defective circuit
h
as been locate d , p roceed
with ste p s 4 through 8 to locate an d re pair the faulty com-
ponents .
4.
V
isu al Chec k. V isually chec k
t
he portion of the in-
strument in wh ich the trou ble is locate d. Many troubles can
be located by visual in d ications such as unsoldered connec-
tions, bro ken wires,
d
amaged circ u it boards,
d
amaged com-
ponents, etc.
5. C heck Ci rcuit Boa rd Interconnections . After the
trouble has been isolated to α partic ular circuit, chec k
t
he
p
in connectors on the circ uit board for correct co nnection.
F igs. 4-5 throug h 4-26 show the co rrect connections of
each board.
The
p
in connectors used in th is i nstrume nt also provide
α convenient means of circuit isolation. For exam ple, if the
4-5