Tektronix 434, Инструкция по эксплуатации

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Q 1 0 9 1 , and Q 1 0 9 4 and th e ir associated c irc u itry make up a
dam per c ir c u it designed to suppress th is ringing.
W hen th e T u rn On c ir c u it generates the tu rn -o n pulse fo r
Q 1 0 8 0 , th e negative m o ve m e n t at the c o lle c to r o f Q 1 0 6 4 is
coupled th ro u g h C 1 0 9 3, C R 1 0 9 2 , and R 1095 to th e base
o f Q 1 0 9 1 . T he re s u lta n t n a rro w negative-going pulse a t the
base o f Q 1091 starts to tu rn o f f Q1091 and Q 1 0 9 4 . The
po sitive m o ve m e n t at th e c o lle c to r o f Q 1 0 6 5 is also
coupled back to th e D am ping C irc u it and a pplied to th e
base o f Q 1 0 9 0 th ro u g h C R 1 0 9 0 and R 1 0 9 0. Q 1 0 9 0 tu rn s
o ff, and its c o lle c to r goes negative, w h ic h serves to ho ld
Q1091 and Q 1 0 9 4 o ff.
When Q 1 0 8 0 is tu rn e d o ff, its c o lle c to r steps p o sitive to
a level d e te rm in e d by th e cla m p in g a ctio n o f V R 1 0 8 5 and
V R 1 0 8 4 . T 1 0 8 5 tra n s fo rm s th is in to a negative m o ve m e n t
at the cathode o f C R 1091 to h o ld Q1091 and Q 1094 o ff.
T h e negative m o ve m e n t at th e c o lle c to r o f Q 1 0 6 5 is applied
to the base o f Q 1 0 9 0 th ro u g h C R 1 0 9 0 and R 1090, tu rn in g
Q 1 0 9 0 on. A b o u t fiv e to ten m icroseconds a fte r th e tu r n ­
o f f tim e o f Q 1 0 8 0 , fly b a c k ends, rin g in g occurs in T 1 0 8 5
and CR1091 tu rn s o ff. Q1091 and Q 1094 are tu rn e d on by
Q 1 0 9 0 and c o n d u c t very h e a vily th ro u g h th e fu ll-w a v e
bridge re c tifie r C R 1096-C R 1099 and one w in d in g o f T 1085
to reduce th e a m p litu d e o f the rin g in g . The dam ping tra n ­
sistors Q1091 and Q 1 0 9 4 th u s c o n d u c t o n ly d u rin g the
tim e fly b a c k rin g in g is o ccu rrin g .
C 1095, C R 1 0 9 5 , and th e tra n s fo rm e r w in d in g connected
to th e cathode o f C R 1 0 9 5 fo rm a half-w ave re c tifie r p o w e r
su p p ly generating a p p ro x im a te ly —5 vo lts to be used in th e
D am ping C irc u it.
R egulator C irc u it
The R egulator C irc u it holds the o u tp u ts o f the Power
S u p p ly re la tiv e ly co n s ta n t despite v a ria tio n s in in p u t line
voltage, lin e fre q u e n c y , and load dem and. R e g u la tio n is
accom plished b y v a ryin g th e tim e in te rva l betw een c u rre n t
pulses c o n d u c te d in th e p rim a ry w in d in g o f T 1 0 8 5 by
Q 1 0 8 0 .
C l 136 and R 1132 com prise a tim in g c ir c u it to d e te r­
m ine th e in te rva l betw een th e regulating pulses. C l 136
charges to w a rd th e voltage level at p in 6 o f U 1 1 3 0 th ro u g h
R 1 1 3 2 and C R 1 1 3 2 . When the charge on C l 136 reaches a
level a b o u t 0.6 v o lt m ore p o s itiv e th a n th e voltage level at
th e gate o f Q 1 1 3 8 , Q 1 1 3 8 co n d u cts c u rre n t to discharge
C l 136 and, at th e same tim e , fo rw a rd bias th e base-em itter
ju n c tio n o f Q 1 1 5 0 , W hen th e c u rre n t flo w th ro u g h Q 1 1 3 8
fa lls b e lo w the level necessary to keep Q 1 1 3 8 o n , Q 1 1 3 8
w ill tu rn o f f and C l 136 w ill s ta rt to charge again.
When Q 1 1 3 8 tu rn s o n , Q 1 1 5 0 , w h ic h is q u ie sce n tly
biased o ff, tu rn s on and co n d u cts a c u rre n t pulse th ro u g h
C irc u it D e s c rip tio n —43 4
th e p rim a ry w in d in g o f T 1 1 5 0 . T 1 1 5 0 couples a negative-
going pulse to the base o f Q 1 0 4 0 th ro u g h C R 1 0 4 0 . Q 1 0 4 0
tu rn s on and its c o lle c to r moves p o sitive to tu rn on Q1Q50,
w h ic h starts th e sequence o f events necessary to generate a
tu rn -o n pulse fo r Q 1 0 8 0 .
T h e tim e interval betw een pulses generated in th e Regu­
la to r c irc u it is altered b y m o n ito rin g v a ria tio n s in the —15
vo lts su p p ly . F or exam ple, w hen heavy load demands are
being made on the —15 v o lt supply it a tte m p ts to go p o si­
tiv e . T h is p o sitive m o ve m e n t results in a p o sitive m ove m e n t
in th e voltage level a t p in 6 o f U 1 130. A m ore p o sitive level
a t p in 6 o f U 1 130 shortens th e a m o u n t o f tim e re q u ire d by
C l 136 to charge to th e level at w h ic h Q 1 138 tu rn s on. T his
results in m ore tu rn -o n pulses being generated fo r Q 1080,
th e re b y increasing the a m o u n t o f energy transferred
th ro u g h T 1 0 8 5 per u n it o f tim e ,
POWER SU PPLY S E C O N D A R Y
General
The Power S u p p ly Secondary c irc u it re c tifie s the A C
voltages present in th e secondary w in d in g s o f Power T ra n s­
fo rm e r T 1 0 8 5 to p ro v id e th e necessary DC s u p p ly voltages
to th e in s tru m e n t c irc u itry . A schem atic o f th is c irc u it is
show n on diagram 10 at the rear o f th is m anual.
R e c tifie r C ircuits
A ll o f th e re c tifie r c irc u its in the Power S u p p ly S econd­
ary are half-w ave re c tifie rs . LI 102, L II0 4 , and LI 106 provide
added filte rin g fo r th e + 1 1 5 v o lt, +1 5 v o lt, and the —15
v o lt supplies respectively. T 1 1 0 0 provides co m m o n -m o d e
in d u c ta n c e to suppress th e 2 5 -k ilo h e rtz inte rfe re n ce
o rig in a tin g in the p o w e r s u p p ly c irc u it. The H igh-V oltage
s u p p ly is a series o f ten half-w ave re c tifie r pow er supplies.
T o ta l o u tp u t voltage o f th e su p p ly is a p p ro x im a te ly 4.1
k ilo v o lts fo r use in the C R T c irc u it. C R 1 1 9 9 provides DC
fila m e n t voltage to th e C R T .
C R T C IR C U IT
General
T h e C R T C irc u it co n ta in s th e c o n tro l c ir c u itr y necessary
fo r o p e ra tio n o f th e cathode-ray tu b e (C R T ). Fig. 3-14
shows a d e tailed b lo c k diagram o f the C R T c irc u it. A
schem atic o f th is c ir c u it is show n on diagram 11 at the rear
o f th is m anual.
U n b la n kin g A m p lifie r
T h e U n b la n k in g A m p lifie r c irc u it c o n tro ls th e C R T
in te n s ity level fro m several in p u ts . T he e ffe c t o f these in p u t
signals is to e ith e r increase o r decrease th e trace in te n s ity ,
o r to c o m p le te ly b la n k p o rtio n s o f th e d is p la y . A p o rtio n
o f integrated c irc u it U 9 4 0 A is used to c o n v e rt th e voltage
3-21