Tektronix 7704A User Manual

VER TICA L A MPL I F I ER
T h
e
Vertical Am p lifier circ u it p rovides final am p lifica-
tion for t
he vertical signal b efore it is app lied to t he vertical
deflection p lates of t he C R T . T h is circ u it includes t h e d elay
line and an
input to prod uce t he vertical portion of α
rea
d out
d is p
lay .
T h e BEAM F I N D ER switc h limits t
h
e
d ynamic range of t h is circuit to compress an over-scanned
d is p lay with in t h e C R T viewing area .
F igure 2-46 s h ows α
d etailed bloc k diagram of t h
e
V
ertical Amplifier circuit .
Delay L ine
Delay Line D L 5050 p rovi d es
approximately 90 nano-
seconds of delay for t he
vertical signal to allow the
h orizontal circuits time to initiate α
swee p before t he
vertical signal reach es t
h
e
vertical d eflection plates of t he
CRT . T h is allows t
h e instrument to dis p lay t he lea ding edge
of t h e signal w
h
en
using internal triggering . T h e delay line is
α coaxial typ e t
h
at does
not pro d uce p res h oot or ph ase
distortion in t
h
e C
RT d is p lay .
In p ut B alance
T h e In p ut Balance stage p rovides vertical trace centering
and an in put from t he Readout System to t
h
e V
ertical
Am p lifier
circuit . Q4479-Q4485
are connecte d as α p ara-
ph ase amplifier . Centering
a
d j ustment R4493 d etermines
t h e voltage level at t he base of Q4485 to set t h e quiescent
DC levels at p ins 2 an d 4 of U 4413 . R4493 is a d j uste d to
vertically center t he trace w h en t he inputs to t h is circuit are
at t h e same potential .
T
h e
Υ - R
ea d out
signal from
t
he
V ERTICAL SIG N A L
FR
O
M VER TICA L
I
NT
ERF AC
E CI R C U
IT

ω
Υ - SIG N A
L .
FR
O M
RE ADO UT SYST E M
Rea d outSystem is connected to t h e base of Q4479 t hrou g h
common-base connecte d Q4470 . T h e paraph ase
amplifier
converts t he single-en d ed Υ -
R
ead out signal to a push-pull
signal to drive t h e Output Am p
lifier .
Outp ut Am p lifier
T h e Out put
Amplifier stage is ma de up of integrate d
circuit U
4413 . T h e circuitry s h own with in t h e s h aded area
on diagram
12 is α representation of t h e internal circuitry
of U4413 .
N otice t h at U 4413 is ma d e up of t h ree similar
push-pull stages
. Eac h stage consists of α common-emitter
transistor
pair d riving α p air of low in put impedance,
common- base transistors . R4439 sets t he gain of t h e first
stage . T hermistor RT4438 provi d es t hermal com
p
ensation
for t he Vertical Amplifier circuit . RC
networ
k
R 4423-C4423- R 4424-C4424- R 4427-C4427 provides
fre-
qu ency compensation
for
t
he first stage . Gain a d j ustment
R4406 sets t he gain of t h e secon d stage to determine t
h e
overall gain of t he V ertical Am p lifier . C4401- L 4401-
R 4404- L 4410- L 4411 provide fast-rise fre q uency com p ensa-
tion
for
t h e secon
d am
p lifier
stage
. Bias
ad j
ustment R4415
sets t he voltage level at p in 10 of U 4413 to a d j ust
t h e t h ir d am p lifier stage for maximum voltage gain . RC
networ k s R4455-C4455- R 4453-C4453- R 4451-C4451 an d
R4465-C4465-
R
4463-C4463-
R
4461-C4461 p
rovi
d
e fre-
q uency com p ensation for
t
he
t
h ir
d
stage .
BEAM
F
I
N
D
ER
switc
h
S5007A
disconnects
t
h e groun d
return for t h e t h ird stage in U4413 to p rovi d e t h
e
beam
finder function . T h is limits t h e d ynamic range of t h is stage
by limiting its current, so t h e d isplay is compressed
vertically with in t he graticule area .
ΙΒΕΑΜ F I ND ER
S5o07A
F ig . 2-46 . V ertical Am p lifier
circ u it detailed b loc k diagra m .
Circuit Description -7704A Service
VER TICA L DE FLE CTIO N
SIG
N
AL
TO
C R T
_

D EFLE CTIO N PL AT E S
2- 5 7

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English