Tektronix 2235 User Manual

Th eory of O p eration-2235 Service
sig n als t h at are used to gen erate correct timing of t he crt

Α swee p
ram p
is
initiated w h en 0576 is biase d off . T h is
u
nb lan k ing and intensity levels used for viewing t he d is p lay .

will b ias off Q701 and t
h
e
timi ng
cap acitors can
charge at α
See
Figure 3-3 for t he b loc k d iagram of t he Α Swee p Ge n er-

rate dete r mined by timing resistors
R 701
and
R 702 and t he
ator
a nd L ogic ci r cuitry .

p ositio n of
Α
S
E
C/DI
V switc h S701 . O ne end of timing resis-
tor R 701 is co
n
nected to
t h
e
wi p er of R 721 and t h e ot h er
end is con nected to
t h
e
in p u t
of
t he M ille r i n tegrator . D u e to
T h e Sweep L ogic circ u it r y controls t he h ol d off time,

feed bac
k from t h
e
circ u it o u tput t hrough t h e timi ng capaci-
starts
t h e sweep upon reception of α trigger signal, a nd ter-

tors, t h e i n tegrator inp u t voltage
remains fixe d a nd esta b -
mi
n
ates
t h
e swee p
at t he prope r swee p level . Wh en using

lis hes α constant voltage across t
h
e
timing resistors . T h is
Ρ - Ρ A u to or TV F ield triggering, t he Sweep L ogic circ u itry

constant voltage,
w h
ic
h p
ro du
ces α con stant current
will cause t he Swee p Ge n erator to free run, produ cing α

t h roug h t h e timi
ng
capacitors,
res u lts i n α li n early increasi ng
b aseli ne t r ace if α trigger sig n al is not received wij : h i n α p re-

voltage at t he output of
t h
e
Α M iller Sweep circuit .
determi ned time period .
Α M ille r Sweep Gene r ato r
T he Α Miller Swee p Generator p ro duces α linear voltage
ramp t h at drives t he H orizo n tal Amplifie r . It produces t h is
r am p b y maintaining α con stant cu rre n t t hrough timing ca-
p acitors to obtain α li n early inc r easing voltage .
Field-effect transistors Q704A and 0704 Β are matc hed
d evices wit h Q704 B sou rci n g current for 0704 Α . Si n ce t he
gate and source of Q704 B are connected toget h er, t he
sou rce current of Q704A will b e of α magnitude suc h t h at
t h e r e is no voltage dro p across its gate-sou r ce j unctio n .
T h e Sec/Div V aria b le circ u itry u tilizes an operational am-
p lifier
to
mai n
tain α co
n
sta
n
t refere
n
ce voltage at one end of
Wh en t he swee p is n ot runni n g, 0701 is biase d on to

R 721 i nd epen d ent of t he circ u it load
.
T h
e voltage ap p lied to
h old t h e timing cap acitors in α disc harged state .
T
he low

t he timi ng resistors varies wit h t h e rotational position
of
im p eda nce of Q701 in t he fee db ack p at
h h
olds t
h
e
Α M iller

R721, t he S E C/DI V V ariable control . Α fixed
do voltage is
Swee p out p ut near ground p ote n tial
.
T h e voltage across

applied to
t h
e
noninverti ng in p
ut of t
h
e op eratio
n
al am
p lifier
Q701, i n addition to t h e base-emitter voltage of Q706, pre-

and feedbac
k
resistors
R 717
and
R 718
esta b
lis h
d oub le
vents saturatio n of t he output device .

t h
at voltage at
t h
e anode of
VR 720
.
3- 1 0
T R IGG ER
SIG N A LS
FR
OM THE

Α S WEEP
Α TR IGG ER A UTO

L OG I C
CI RCU I T R Y

Ι B ASEL I NE

U532 B ,
U5Θ2Β , U 5θ
4
Α ,

U 5 θ2Α ,
Q ςφ 9

U5 Φ 6
Α ,
U 5Θ 6Β ,
U506C
H OLOOFF
U504 B
SI N GLE
SW EEP
U 532A
END-O F -S WEEP
Q525
Wh en t h e o u tp u t reac hes a pp roximately 12 V, t he Swee p
L ogic circuitry will initiate t h e h oldoff p eriod i n w h ic h Q701 is
turne d on an d t he Α Swee p Generator is r eset . T h is h oldoff
p eriod is n ecessary so t h at t h e timi ng cap acito r s can be fully
d isc harged b efore anot h er sweep starts . Capacitors C702
and C703 are always i n t h e ch arging circuit and are used for
h ig h swee p s pee d s . Ca p acitor C701 Α i n series wit h C701 Β
are used for medium sweep speeds, and C701 Β is used for
slow swee p speeds .
Α
SW EEP
G ENER ATOR
Q701, Q7Θ4 Α ,
0704B, 0706,
U715
F ig ur e 3-3 . B loc k diag r am of t he Α Swee p Ge ne r ato r a n d Logic ci r cu it r y .
TO
H OR I ZO N TA L
A MPL I F I ER
42θ6-13

Tektronix 2235 Specifications

General

Brand	Tektronix
Model	2235
Category	Test Equipment
Language	English