Tektronix 7704A User Manual

During
time T1-T2, con d itions are
reversed
.
Since Q2 is
biase d off, t
h ere is no cu rrent t h roug
h
it an
d C2510-C2511
b egins to
d isc h arge t h roug
h R 2512- R 2513 . T h e emitter
level of Q2 follows t he d
isc h arge of C2510-C2511 until it
is
about 0 .6 volt more
negative t h an t he b ase .
T h
is
forwar d
b iases Q2 and
its collector drop s negative to
reverse- b ias
Q1 . T h
e
level at
pin 14 drops negative also, to
com p lete t he
cycle .
O n ce again, C2510-C2511
begin to ch arge t h roug h
R 2510-132511 to start t
he secon d cycle . Wh en S2510 is set
to t h e 2- MH
z position, R 2512 is byp assed and
one end of
C2511 is d
isconnecte d from t he RC timing
circuit . T h e
decrease
d
R C time allows C2510 to
c h arge and d isc h arge at
α two-mega
h ertz rate .
Two outputs are provi d
e
d by
t h is oscillator : T h e Delay
R am p signal from Q1 or Q2
is connecte d to t h e Vertical
C h oppe d Blan k ing stage,
and α sq uare-wave outp ut
from
pin 14 . T he s q uare wave
at pin 14 is connecte d to pin 16
t h roug h an external capacitor,
C2510 . C2510 d ifferentiates
t h e s q uare wave from pin 14 to p
roduce α negative-going
pulse coincident wit h t
he falling edge of the s q uare wave
(see pin-16 waveform on
Fig . 2-15 Β ) . Th is negative-going
pulse is connected to
pin 15 t h ro ug h an inverter-s
h
aper
w h ic h is p art of
U 2510 . T h e resulting output at p in 15
is
α
positive-going Cloc k p ulse at α
r epetition rate of eit
h er 200
k
ilo h ertz or two mega
h ertz, depending on t h e p osition
of
S2510 .
V ertical C ho pp e d B lan
k ing
Circuit
Descriptio n - 7704A
Service
Th e Vertical C h oppe d
Blan k ing stage is ma d e up of t
h e
remainder of U 2510 .
T h
is
stage dete r mines if Vertical
C h oppe d Blan k ing pulses
are
re
q uire d , base d upon the
op
erating mo de of t he
vertical system or t he pl u g-in units
( du al-trace units only) .
Vertical C hopped Blan k ing p
u lses
are produced if : 1 .
VER TICA L M OD E switc h is set
to
C H O P ; 2 . Dual-trace
vertical u nit is operating
in t he
ch opped mo d e an d t
h
at
unit is being displayed ; 3 .
Dual-
trace vertical unit is op
erating in t he cho p pe d mo d e wit
h
t
h e VER TICA L M OD
E
switc
h set to ADD . T h e repetition
rate
of t he negative-going
Vertical C h opped Blan k ing p
ulse
output at p in 4 is 0 .2 or two
mega h ertz for all of t
he
a
b ove
con d itions ( d etermine
d by t he Cloc k Generator stage)
.
Figure 2-16 s h ows α logic d iagram
an d an inp u t/o
u
t p ut
ta b
le for t he Vertical C
h
o pp
e d Blan k ing stage .
N otice t he
com p arator bloc k
on t he d iagram .
T
he
out pu t of t h is
com p arator is
d etermined by t he relations
h i p between t he
levels of its in p uts .
If pin 10 is more p
ositive
(HO
t han t h e
groun d e d
input, t he output is HI also ;
if it is more negative,
t
h
e
output is L O .
CLOCK
To τ
1
Pin 13
P i n 14
J
τ
2
Ι
N
I
ι
ΙΒ )
Fig . 2-15 . ( Α ) Diag
r
am
of Cloc k Generato r stage ; ( Β ) I d
ealize d wavefo r ms for Cloc k Ge n e r ator stage
.
2- 2 1

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English