Tektronix 2235 User Manual

M ainten a n ce-2235 Service
I nsert t h e b ayo n et sig n al ti p to t h e first test poi n t i n dicate d
in Ta b le 6-4 a n d to u c h t h e bayo net ground tip to t h e c h assis
ground near t h e test point . T h e r ipple val u es listed in Table
6-4 are based on α system limited i n band wi d t h to 30kH z
(greater bandwidth will result in h ig h e r r ea d i n gs) .
If power supply voltages and ri p ple are wit h i n t he listed
ra n ges, t he s upp ly can b e assumed to be operati n g correct-
ly . If any are ou tsi d e t hese ra n ges, t he supply may be eit h er
misa dju sted or op erating i n correctly . U se t h e " P owe r Sup-
ply, Display, and Ζ -Axis" sectio n i n t h e "Ad j ustment" proce-
du r e to ad j ust t he -8 .6 V supply .
Α defective component elsew h ere in t h e i n str u me n t can
c r eate t he a pp eara n ce of α power-s upp ly p roblem and may
also affect t he o p eratio n of ot h er circuits .
-8 .6 V

ΤΡ 961

-8 .56 to -8 .64

1 .5
+5
.2 V

W 968

+5
.04 to
+5
.36

3 .0
+8
.6 V

W 960

+8
.43 to
+8
.77

1 .5
+30 V

W 956

+29 .1 to +30 .9

20 .0
+100 V

W 954

+97 .0 to +103 .0

40 .0
7 . C h ec k Ci r cuit B oa rd Inte r co n nections
After t he trou b le h as b een isolated to α p artic u lar circ u it,
again check fo r loose or brok en con nections and h eat-dam-
aged com ponents .
8 . C h ec k V oltages and W aveforms

Wh
en trou b les h ooting tr an sisto r s i n t he circ u it wit h
α
voltmeter, meas u re b ot h t he emitter-to- b ase a nd emitter-to
Often t h e d efective component can b e locate d by ch ec k -

collector voltages to d etermi n e w h et h er t h ey a r e con siste n t
i ng t he a p propriate voltage or waveform in t he ci r cuit . Typ i- .

wit h normal ci r cuit voltages . V oltages across α transistor
cal

voltages

are

listed

on

t h e

sc hematic

d iagrams .

may va r y wit h t he ty p e of device a nd its circuit function .
W aveforms are sh own ad j ace n t to t he sch ematics, and
waveform test p oints a r e indicate d on b ot h t he sc hematics
and ci r cuit board illustratio ns by h exagonal-outlined

Some of t h ese voltage a r e pr e d ictable
.
T h
e emitte
r
-to-
nu m b ers .

base voltage
for
α condu cti ng silico n tra n sisto r will no r mally
NOTE

range from
0 .6 to 0 .8 V . T h e emitter-to-collecto r voltage for
α saturated
t r
ansisto
r
is abo u t 0 .2 V . B eca u se t h ese val u es
Voltages a
n
d
waveforms given
on t
h
e sc
h
ematic d ia-

are small, t h
e best way to c
h
ec
k
t
h
em is b y con necting α
grams
a
r
e
not
absol u te and may vary
slig h tly
between

se n sitive voltmete r
ac
r
oss t
h
e j unctio
n r
at
h
er t han compar-
ί n stru me n ts . To establis h o p e r ati n g cond itio ns similar

ing two voltages ta ken wit h res p ect to
ground .
If
t
h
e fo
r
me r
to t
h
ose used to ob tain t
h
ese readings, see t
h
e "Volt-

met
h
od is used, b ot
h
lea d s of t h e voltmeter must be isolate d
ageand
W
avefo
r m
Setup" conditio
n
s
i n
t
h
e "Dia-

from
ground .
gr
ams"
sectio n for t he p relimi n ary eq uipment
setu p .
N ote t he recomme nd ed test e qu i p me n t, i n itial front-
pa
n el co n t r ol setti n gs, a nd ca b le-co nn ectio n i n st
ru c-

If values less t h
an
t h ese are
obtained,
eit h
er t
h
e device is
tions . The control-setting c han ges (from initial setup)

sh orted or no current is flowing i n t he exter n
al
circuit . If
requi
r
ed to obtain
t h
e
given
waveforms and voltages

val
ues exceed t
h
e emitte
r
-to-base
val
u es give n , eit he r t he
are located on
t h
e
waveform-diagram
page .

j
unction
is reverse b iased or t
h
e d evice is d efective . V olt-
6-8
Table 6-4
P owe r Supp ly L imits a nd R i pp le
P ower

Test

R ea d i ng

Ρ - ΡR i pp le
Su pply Point ( V olts) (m V )
WA RN I N G
To avoi d electric sh oc k , always discon n ect t he i n str u -
ment f r om t h e p owe r input so u rceb efore removing or
re p lacing com ponen ts .
9 . C h ec k Individual Com pon e n ts
T he following p roce du res d escri be met h ods of ch eck i ng
individual components . Two-lead com ponents t h at are sol-
dered in p lace are most accurately checked by fi r st d isco n -
n ecti n go ne end from t h e circuit boa r d . T h is isolates t h e
meas u reme n t from t he effects of su rr oun di ng ci r c u itry .
See
F igure 9-1 for value ide n tificatio n or F ig u re 9-2 for typical
semiconductor lead configuratio n .
CA U TIO N
Wh en chec k i n g semico ndu ctors, observe t he static-
se n sitive p recautions locate d at t he begi nn ing of t h is
section .
TRA N SISTO RS . Α goo d c h ec k of tra n sistor operation is
actual performa nce unde r op erati n g cond itio ns . Α transistor
can most effectively be ch ec ked b y sub stit u ti ng α kn ow n
goo d com p o nen t . H owever, be s u re t h at circuit con d itions
are not such t h at α re p laceme n t transistor mig h t also b e
d amaged . If substitute transistors are not availa b le, u se α
dynamic tester . Static-ty pe testers are not recommended,
since t hey d o n ot ch ec k o pe r atio n und er simulated operat-
ing conditions .

Tektronix 2235 Specifications

General

Brand	Tektronix
Model	2235
Category	Test Equipment
Language	English