Tektronix 454A - Page 98

Ci r cui t Descr i p t i on- 454zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA ‘ / R 454A
nect e
d t o t h e p osi t i ve si d e of t h i s ci r cui t
t o p r od uce ±

Two a d j ust ment s cont r ol t h e t r ace
al i gnment
by
var yi ng
c h ange i n o u t p ut vol t age t o cont r ol C
R
T
i nt ensi t y, Å· -

t h e magnet i c f i el d ar o u nd t h e C R T . T h e
¥
Axi s Al i gn
bl an k i ng, dual - t r ace bl an k i ng and
i nt ensi t y mo d ul at i on .

a d j ust ment ,
R 1485, cont r ol s t h e c u r r ent t h r oug h L 1485
w h i c h af f ect s t h e C R T b eam af t er ver t i cal d ef l ect i on, b u t
bef or e h or i zont al def l ect i on . T h e T R AC E R OTATI O N
C R T
Cont r ol
Ci r cui t s

a d j ust ment , R1480 cont r ol s t h e c u r r ent t h r oug h L 1480 an d
af f ect s bot h ver t i cal an d h or i zont al r ot at i on of t h e beam .
F ocus of t h e C R T d i s p l ay i s
cont r ol l e d by t h e F OC U S
cont r ol , R1467 . T he d i vi d er 1311463- 131469
i s connect e d
bet ween t h e C R T cat h o d e s u pp l y
an d gr ou n d . T h e vol t age

E
xt er nal – Axi s I n p ut
app l i e d t o t h e f oc u s gr i d i s mor e p
osi t i ve ( l ess negat i ve)
t h an t h e vol t age on ei t h er
t h
e
cont r ol gr i d or t h e C R T

‘
si gnal a pp l i ed t o t h e – AXI S I NPU T connect or i s
cat h o d e . T h e
ASTI G a d j u st ment , R 1489, w h i c h i s use d i n

a p p l i e d
t o
t h e C R T cat h o d e t h r o u g h C1479- R 1477- C1477
con j u nct i on wi t h t h e
F
OC U S
cont r ol
t o
p r ovi d e ± wel l -

an d t o t h e – Axi s Am p l i f i er ci r cui t . L ow f r e q uency Z- axi s
def i ne d d i s p l ay, var i es t h e p osi t i ve
l evel
on
t h e ast i gmat i sm

si gnal s ar e pr event ed f r om d i r ect l y af f ect i ng t h e C R T
gr i
d .

ci r c u i t by C1477 . T h ey ar e connect e d t o t
h
e
–
Axi s Am p l i -
f i er ci r c u i t t o pr o
d
uce an
i ncr ease or d ecr ease i n i nt ensi t y,
d e p en d
i ng
upon p
ol ar i t y . C1477 coupl es h i g h - f r e q uency
T h e Geomet r y
a d j ust ment , R 1482, var i es t
h
e p
osi t i ve

si gnal s t o t h e C R T cat h o d e t o pr o d u ce t h e same r esul t ant
l evel on
t h e h or i zont al d ef l ect i on p l at e
s h i el ds t o cont r ol

d i spl ay as t h e – Axi s Am p l i f i er ci r c u i t p r o d u ces f or l ow-
t he over al l geor net r y of t h e
d
i spl ay
. T h e +100- vol t so u r ce

f r e q u ency i nt ensi t y- mo
d u l at i on si gnal s . T h i s conf i gur at i on
f or t h i s cont r ol i s p r ovi
d
e
d by zener d i o d e VR 1356 i n t h e –

o p er at es as ± cr ossover net wor k t o p r ovi d e near l y const ant
Axi s Am p l i f i er ci r cui t
.

i nt ensi t y mo d ul at i on f r om DC t o 50 mega h er t z .