Tektronix 7704A User Manual

M
aintenance-7704 Α Service
3 . V isual Ch eck .
V isually check t h e
p ortion of t he
instrument in w h ic h t h e trouble
is locate d .
Many troubles can
b
e
locate d by visual indications
suc h as unsol d ere d
connec-
tions, brok en wires,
damage d circuit boar d s,
damage d
components, etc .
4 .
C heck Instrument Cali b
ration . C heck t h e
calibration
of t
h
is instrument, or t he
affecte d circuit if t he
trouble
ap p ears in one circuit
.
T
he apparent trouble
may only be a
result
of misa d j ustment or may
b
e
corrected by calibration .
Complete
calibration instructions
are given in t h e Cali b ration
section .
5 . Isolate
Trouble to α Circuit
. To isolate trouble
to α
particular
circuit, note t h e trouble sym p
tom . T he symptom
often i d entifies
t
h
e circuit in w h ic h t he
trouble is located . F or
example, poor focus
indicates t h at t h e C R T
circuit (inclu d es
Auto F
ocus circuits) is p robably
at fault . Wh en
trouble
symptoms
appear in more t h an one
circuit, chec k affecte
d
circuits by
ta k ing voltage an d waveform
readings . Also chec
k
for t h e correct
output signals at
t
h
e rear- p anel ou
t p ut
connectors wit h α
test oscilloscope . If t h e sig
n al is correct, t h e
circuit is wor k ing correctly
up to t h at point
.
F
or example,
correct
sawtoot h output
indicates t h at t h e time-base
unit an d
sawtoot h ou t portion of
t h e Out put Signals
circuit is
operating
correctly . If α malfunction
in t he Rea d out
System
is suspected
of causing trouble
to a pp ear in t he Ζ -Axis
Am p lifier, V
ertical Amplifier,
or
H
orizon tal Am p lifier
circuits, t h e
tro ub le can be localize
d by removing
t
h
e
Rea d out System
circuit board . T h
is boar d can b e remove
d
with out
affecting t h e op eration
of oth er circuits in
t
h
e
instrument .
Incorrect op eration
of all circuits often
indicates trouble
in t he power sup p ly .
C heck first for correct
voltage of t h e
in d ivi d ual supp lies . H
owever, α defective
component else-
w h ere in t he instrument
can a p pear as
α p ower-su pply trouble
and may also affect
t
h
e operation of oth er
circuits .
If
incorrect op eration
of t h e power sup p lies
is sus p ected ,
connect
t
he
7704 Α to α variable
autotransformer . T h
en,
c h
eck eac h p ower su pp ly
for correct regulation
with α DC
voltmeter
(0 .1% accuracy), an d
correct ri pp le wit h
α test
oscilloscope,
w h ile varying t h e
autotransformer t h roug h
out
the regulating range
of t h is instrument
(see rear- p anel L ine
Selector for
regulating range) . Ta b le
3-1 lists t he tolerances
of t he power sup p
lies in t h e 7704 Α . T h
ese voltages are
measure d b etween
t he p ower-su pp ly
test poin ts an d ch
assis
groun d . ( P32G
connects to t h e L.V .
Regulator boar d i n t h e
p ower unit ; Ρ
43
co
nnects to t h e rear
of t h e H orizon tal
Am p lifier board .)
P ower-s upp ly
test
p
oints are s h ow n
on
page 6-31 in t
h e Diagrams section
. If α power-sup p ly
volt-
age is with i n
t h e listed
tolerance, t he supply
can be as-
sumed to be
wor k i ng correctly .
If outsi de t he
tolerance, t h e
sup p ly may be
misad j uste d or o p
erating incorrectly .
U se
t h e procedure
given in t he Cali b ratio
n section to ad j
ust t h e
p ower su pp lies .
3-4
TA BLE 3-1
P ower Supp ly Tolerance an
d Rip p le
(reference d to ch assis
groun d )
F igure
3-2 provides α gui d e
for locating α defective
circuit . Start
at t
he
top of t h e c h art an d perform
t h e c heck s
given on t he left
si d
e
of t h e page u ntil α step
is foun d t h at
does
not p
ro
d
uce
t h e indicate d results . F urt h
er check s, or
t h e circuit in
w
h
ic h t he trou b le is proba
b ly located, are
liste d to t h e rig h
t of t h e ste p . T h is c h art d
oes not include
check s for
all
p ossible
d efects ; use steps 6
an d 7 in suc h
cases .
After t h e d efective circuit
h as been locate d ,
proceed
with
ste p s 6 and 7 to locate
t
h e
d efective com ponent(s) .
6 .
C h ec k V oltages an
d Waveforms . Often t h e
defective
com p onent
can be locate d by c hec
k
ing
for t h e correct
voltage or waveform
in t he circuit .
7 .
C heck In d ivi du al Com p
onents . T h e following p
ro-
ce d ures descri be met h
ods of c heck ing indivi d ual compo-
nents in t he 7704 Α .
Components t h at are soldere
d in place
are b est c heck e d
by first d isconnecting one en
d . T h is
isolates t h e measurement
from t he effects of surroun
d ing
circuitry .
Α . S EM ICO N
DU CTO R S .
P
ower switch mustbe
turned off before removing
or
rep/acing
semiconductors .
Α goo d c heck
of transistor operation is
actual
p
erform-
ance un d er operating
con d itions . Α transistor
can be most
effectively c heck
ed by substituting α newcom p
onent for it
(or one w h ic h h
as been c heck e d p revio u
sly) . H owever, be
sure t h at circuit con
d itions are not such t h
at α replacement
transistor mig h
t
also
be d amage d . If substitute
transistors
are not available,
use α d ynamic tester .
Static-ty p e testers
are not recommen d e
d , since t hey do not chec
k o p eration
un
d er simulated op erating con
d itions .
P ower
Su
p
ply Test Point Tolerance
Typical ri pp le
( peak -to- peak
)
-50
V
olt
p
in 6- P 32G ±0 .20 volt 2
millivolts
-15 V olt p
i n 1- P 32G ±0 .15 volt 2
millivolts
+5 V olt p
in 2- P 32G ±0 .10 volt 2 millivolts
+15 V olt p
in 4- P 32G ±0 .15 volt 2 millivolts
+50 V
olt p in 5- P 32G ±0 .50 volt
5 millivolts
+155 Volt] p i n 1- Ρ 43 ±5
.0 volts
500
millivolts

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English