Tektronix 434, Инструкция по эксплуатации

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C irc u it D e s c rip tio n —4 3 4
C A L IB R A T O R
General
The C a lib ra to r c irc u it produces a square-wave o u tp u t
w ith accurate a m p litu d e and fre q u e n c y . T h is o u tp u t is
available as a square-wave voltage at th e PROBE C A L 0 .6 V
1 kH z c o n n e c to r. Fig. 3-15 shows a detailed b lo c k diagram
o f the C a lib ra to r c irc u it. A schem atic o f th is c ir c u it is
show n on diagram 11 a t th e back o f th is m anual.
M u ltiv ib ra to r
Q 9 0 5 and Q 9 1 0 along w ith th e ir associated c irc u itry
com prise an astable m u ltiv ib r a to r. Basic fre q u e n c y o f the
m u ltiv ib ra to r is d e te rm in e d b y th e RC c o m b in a tio n o f
R 9 0 6 , R 910, and C 906. R 904 provides a measure o f a d ju s t­
m e n t o f C a lib ra to r fre q u e n c y .
In th e C a lib ra to r M u ltiv ib r a to r, Q 9 0 5 and Q 9 1 0 are
never b o th c o n d u c tin g a t th e same tim e . Assum e fo r
purposes o f e x p la n a tio n th a t Q 9 0 5 has ju s t tu rn e d o f f and
Q 9 1 0 has tu rn e d on. W hen Q 9 0 5 tu rn s o ff, its c o lle c to r
moves p o sitive , w h ic h also p u lls th e base o f Q 9 1 0 p o sitive .
T h is po sitive m o ve m e n t tu rn s Q 9 1 0 on and charges C 906
p o sitive . Im m e d ia te ly , th e e m itte r o f Q 905 begins to
discharge to w a rd —15 vo lts . W hen the Q 9 0 5 side o f C 906
has discharged s u ffic ie n tly to fo rw a rd bias th e base-em itter
ju n c tio n o f Q 9 0 5 , Q 9 0 5 tu rn s on and its c o lle c to r moves
negative. The negative m o ve m e n t at the c o lle c to r o f Q 9 0 5
tu rn s o ff Q 9 1 0 . N o w the e m itte r c ir c u it o f Q 9 1 0 begins to
discharge to w a rd —15 vo lts. W hen th e Q 910 side o f C 906
has discharged s u ffic ie n tly to fo rw a rd bias the base-em itter
ju n c tio n o f Q 9 1 0 , Q 9 1 0 tu rn s o n . A t the tim e Q 9 1 0 tu rn s
o n , a p o sitive m o ve m e n t is coupled fro m th e e m itte r o f
Q 9 1 0 to th e e m itte r o f Q 9 0 5 b y C 906. T h is p o sitive m o ve ­
m e n t a t the e m itte r o f Q 9 0 5 reduces th e c u rre n t flo w
th ro u g h Q 9 0 5 , causing a re in fo rc in g p o sitive m ove m e n t at
F ig . 3 -1 5 . C a lib r a to r d e ta ile d b lo c k d ia g ra m .
th e base o f Q 9 1 0 . Q 9 0 5 ra p id ly tu rn s o f f as Q 9 1 0 tu rn s on.
The square wave signal at th e c o lle c to r o f Q 9 1 0 is connec­
ted to th e O u tp u t A m p lifie r.
O u tp u t A m p lifie r
The o u tp u t signal fro m th e C a lib ra to r M u ltiv ib ra to r
stage overdrives Q 9 1 5 to p ro d u ce an accurate square wave
a t th e o u tp u t. W hen th e base o f Q 915 goes p o sitive , Q 9 0 5
is c u t o ff and the o u tp u t signal d rops negative to gro u n d .
W hen the base goes negative, Q 9 1 5 is d rive n in to s a tu ra tio n
and the c o lle c to r o f Q 9 1 5 rises p o sitive to a b o u t + 1 5 volts.
T he o u tp u t voltage is con n e cte d fro m th e voltage d iv id e r
R 9 1 5 -R 9 1 6 -R 9 1 8 to th e PRO BE C A L 0.6 V 1 k H z co n n e c­
to r. R 915 adjusts th e overall ra tio o f th e voltage d iv id e r to
p ro vid e an accurate o u tp u t voltage a m p litu d e .
S T O R A G E C IR C U IT
The Storage C irc u it provides th e voltage levels necessary
to operate th e flo o d guns, c o llim a tio n electrodes and ta rg e t
backplates. T he storage ca th o d e -ra y tu b e has tw o targets
fo r split-screen o p e ra tio n ; th e re fo re , tw o id e n tic a l erase
generators are p ro v id e d , each consisting o f an Erase M u lti­
v ib ra to r and a T a rg e t C o n tro l A m p lifie r. These c irc u its
p ro d u ce an erase w a v e fo rm w h ic h w ill erase w ritte n in fo r ­
m a tio n . A d d itio n a l c irc u itry includes th e Enhance Genera­
to r , w h ic h p e rm its very fa st single sweeps to be sto re d , and
th e IN T E G R A T E s w itc h , w h ic h p e rm its a stored image o f a
nu m b e r o f re p e titiv e sweeps, each o f w h ich w o u ld be to o
fast to store alone as a single sweep event. Fig. 3-16 shows a
d e ta ile d b lo c k diagram o f th e Storage C irc u it.
Storage Tube Basic O perating Principles
The C R T used in th e 4 3 4 is a d ire c t-v ie w storage cathode
ray tu b e w ith a s p lit screen view ing area th a t p e rm its each
h a lf to be in d iv id u a lly operated fo r stored displays. Storage,
w h ic h is the re te n tio n on th e C R T screen o f a displayed
event, is based on a secondary emission p rin c ip le . A stream
o f p rim a ry electrons strikes an insulated ta rg e t surface w ith
s u ffic ie n t energy to dislodge secondary electrons. As the
p o te n tia l increases, each p rim a ry e le ctro n dislodges m ore
th a n one secondary e le c tro n , re su ltin g in the ta rg e t m aterial
charging po sitive . T he ta rg e t approaches the b a ckp iate
p o te n tia l, y ie ld in g a higher energy flo o d e le ctro n and
re su ltin g in lig h t o u tp u t.
T he storage cathode ray tu b e co n ta in s special storage
elem ents in a d d itio n to th e co n v e n tio n a l w ritin g gun
elem ents. The o p e ra tin g m ode o f th e tu b e depends
p rim a rily on th e voltages applied to these storage elec­
trodes. W ith one c o n d itio n o f applied p o te n tia ls , th e
storage screen o r ta rg e t b a ckp iate operates in th e ready-to-
w rite state; th e n , w hen it is b om barded w ith high energy
w ritin g beam c u rre n t, th e b om barded p o rtio n s h ifts to the
stored m ode to store a w ritte n d is p la y . W ith a d iffe r e n t set
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