Tektronix 2235 - A Sweep Logic; ALTERNATE Β SWEEP

Α Swee p L ogic

of U 532D
is h eld L O b y R 569 and t h eo u t p ut
will follow t h e
T he Α Sweep L ogic
circuitry controls swee p ge n eration,

signal
p rovi d e db y t he Q out p ut of U 502
. If trigger sig n als
as α functio
n
of
incoming trigge r signals and t he Α
Tr igger

are b eing received by U 502, t he out p ut of
U 532D will b e HI
mode selected .

and cause t h e outp ut of U 532C to b e L O .
F lip-flop U 506A
will res p ond to trigger signals as descri bed
in t he "N O RM"
section
. If trigger signals are not being receive d
b y U 502,
I n coming trigger signals from t h e out p ut of
U 480 B will

the outp
u t of U 532D will be L O . T he outp ut of U
532C will
cloc
k
U
502, α one-sh ot m u ltivi b rator, and cause
t he Q out-

then
be t he inverse of t he in p ut signal a p plied
to p i n 11 so
t
h
at
U 506A will b e reset w hen h ol d
off
ends,
causing α
p ut
to go from L O to HI . If anot h er
trigger sig n al is not

sweep
to be generated . W it h no new trigge r p u lses b
eing
received b y U 502 wit h i n α time p eriod
determined by t he

applied
to
t he circuitry, U 506A will b e contin u ously
set a nd
time constant of R 503 an d C501, t
h
e Q
o u t p ut will ret u r n
then reset
in t h is manner to generate swee ps .
L O . Wh enever trigger sig n als are b ei n g received, t
h
e
0 out-
p ut of
U 502 will b ias on Q509 a nd ill u
min
ate
TR IG'D LE D
DS518 . T he ou tput state of U 502 is u sed
i n t h
e
A u to B ase-

SG L SWP . In t
h
e Sgl
Swp mode, bot h t he Ρ - Ρ A U TO and
line circuit as desc r ibe d in t h e "P- Ρ A U TO an
d TV F I EL D"

N O RM bu tto
n
s are o
u t . T h is results in α L O at t he output of
section .

U 532C so t h at U
506A
is
not h eld reset . Α L O is also on
i n put p in 4 of U 532A
.
N O RM . Wh en N O RM Trigger mode is
selecte d , input p in
12 of U 532D is h eld HI b y S401 Β , causing
t h
e
gate out p ut
to
also be HI . T he out pu t of U 532C
will t h
en
b e L O and
U
506A will not b e h eld reset . Inp u t p
i n 4
of
U 532A is h el d HI
by
S401 C, causing t he output to b e
L
O
w h ic h p laces α L O
on
t he D inp u t of U 506A . Trigger sig n als receive d at
t h
e
cloc
k input of U 506A will t hen cloc k t h is L O to t
h
e Q
o u t p ut .
During t he previous
h
oldoff
period, U 506A h ad b een set
b yU 532 B so t h at t
h
e Q
o u t p ut went L O . T h is b iase d on
Q576 and t h e
Α M iller Sweep was p revented from r unning .
Wh en ever U 506A is
cloc ked followi ng h oldoff by α trigger
sig n al, t he L O on t h eD in p ut
will
be
transferred to t he Q
output and t h e 0 out p ut
will go Hl . T h is will b ias off 0576
and t he ΑM iller Swee p
will generate t h e swee p ram p as
described in t h e " Α M
ille r Swee p Generator" section . Wh en
t he ramp voltage is ab out
12 V, Q525 will b e b iased on . T he
outpu t of U 532 B
will
c
h ange f r om L O to HI, setting U 506A
and b iasing on 0576 . W it h Q576 con
d ucti n g, h ol d off o n e-
sh ot U 504 B will be
trigge r
ed
and t he Α M iller Sweep Gener-
ator will be reset to turn
off Q525 .
Th eory of
Ope r ation-2235 Service
During t he p revious
h oldoff p erio d , U 532 B had reset
U 506 B to cause t
h
e Q o
u t pu t to be L O . T he D in pu t of
U 506A will t h erefore b e HI and cloc
k signals to t he gate will
k eep t he Q output L O and t
h
e
swee p disabled . Wh e n t he
SG L SWP b utto n is pushe d
i n,
t
h
e Q
o u t p ut of U 504A will
go L O for α time p eriod
determined b y t he time con stant of
R 504 and C504 and t
h
e
n return
HI .
T h is ΗΙ will t hen cloc k
t hrough t he ΗΙ on t
h
e
D in p
ut
of U 506 B to t h e Q out p ut .
Conse quen tly t he o u t p ut of U
532A will go L O and C R 514
will b e reverse biase d to b ias on
Q511 and lig h t t h e RE ADY
LE D . T he next trigger p ulse app
lie d to t he cloc k i n put of
U 506A will t hen initiate α
swee p as descri b ed p reviously . At
t he end of t he swee p , U 506
B will again be reset, causing
t heTR IG'D LE D to go out an
d p lace α HI on t he D in p ut of
U 506A . Α n ew swee p will
n
ot b e
initiated until t h e SG L SWP
button is again p ush e d .
Χ - Y . In t he Χ - Υ mode of
operation, t he ΧΥ li ne is L O
w h ic h h olds t he input of U 532
B L O t h ro ugh CR 518 . T he
outpu t of U 532 B will h old U
506A set an d
no
swee p s can be
initiated .
W it
h
U 504
B t r iggered, t h e Q out p ut c h anges from HI to
L O and
will
stay
L O for α time duration dete r mined by
t h
e
V ar H oldoff
circuitry and t h e Α SE C/DI V switc h position
.

AL T ERN AT EΒS
WEEP
V AR H O
L
DO
FF p otentiomete r R 9521 determines t
h
e
amou
n
t of c
h arging curre n t available to ch arge C518, C519

T h
e
Alternate Β Swee p circuitry, sh
own
on
Diagram 5,
or C520 at
pin 15 to t h e t h res h ol d voltage level on
p in 14 .

p
roduces
α linear voltage r am p t h at is amplifie db y t
h
e
H ori-
During t
h
e
time t he Q out p ut is L O, t he set input of U 506A is

zontal
Amplifier to provide t he Β Swee p
h orizontal deflec-
h eld HI so t
h
at no
trigger p ulses can initiate α n ew sweep .

tio
n
on
t h e crt . T he Alternate Β Swee p
circ u itry also
Wh en pin 15 of U
504 B reac hes t he t hr esh old voltage on p
in

p
roduces
t he swee p -switc h ing signals t
h
at
control t he dis-
14, t h e i5 out
pu t goes HI to e nd t h e h ol d off p eriod and re-

play of t he Α and Β Sweeps, and t
h
e
gate signals u sed by
lease U
506A from t he set condition . The circ u it is
t h
en
en-

t he Intensity and Ζ -Axis circuits
to establis h t he crt
ab led
to gen erate anoth er swee p once α
trigger signal is

unblan k i ng and inte n sity levels nee ded fo
r p ro du cing b ot h
again
app lied to t h e cloc k input of U 506A .

t h e Α Intensified and Β Sweep d isplays .
Ρ - Ρ A U TO and TVF I EL D . Wh en Ρ - Ρ Auto or
T VF ield is

T h e Β Swee p ram p is e
n
able
d by t h eΒ Sweep L ogic
selected, t he Auto B aseline con figuration is e
n
abled .
P in 12

circ u it eit h er immediately after
t h e end of t h e esta b lis hed
3- 1 1