Tektronix 7704A User Manual

Α and ΒTR IGG ER
SO UR C E
switc
h positio n s
' P i n 14
L O
fo r all ot h er con d itions .
F ig . 2-21 . I n p ut levels at pin
4 of U 2404 an d U 2424 (so u rce of
triggering sig n al is s h own
i n p a r ent h eses)
.
2 . A LT VER TICA
L M OD E
Depressing
t he A L T button of t he
VER TICA L MOD E
switc
h
app
lies +5 volts to t
h
e ano d
e
of
CR 1067 to turn it
on . Current t h roug
h
C
R 1067 forwar d biases Q2090 into
saturation, causing t h
e voltage at pin 4 of U 2404 to follow
t h e MF ( M ain
F rame) C h annel Switc h Signal (Dis p lay
R ig h t) as it switc
h
es
between HI ( R IG H T
VERT
d isplay)
and L O (LEF
T VER T d is p lay) at t h e en d of eac
h swee p . At
t he same
time, p in 14 is held L O t h roug h C
R
1064
and
C R 1065 . As α
result, t h e swee p for t he R IG H
T VER T
dis p lay is
triggere d by t he R IG H TVERT signal, an
d t he
sweep for t
he LEF T VER T d is p lay is triggere
d by t he
LEF T VERT signal .
3 .
ADD O R CHO P VER TICA L MOD E
For t h ese two
modes, Q2090 is not biased
on, so pin 4
of U 2404 is
h el d L O by t he negative voltage a pp
lie d
t h roug h
R
2095 .
P in 14 will be Η Ι d ue to
t h e p ositive
voltage a p
plie d t h roug h CR 1064 or C
R
1065 .
As
indicate d by t he input/output table,
w h en pin 4 is
L O and p
in 14 is HI, t h e trigger output
signal is t h e
alge b raic sum of t h e trigger
input signals from t h e LEF
T
VER T an d R IG H T VER
T com p artments . T h is prevents
triggering on t he vertical
c h
o pp
ing transition of α CH O P
d is p lay, an d on only
one signal of an ADD d isplay .
4 . R IG HT VER TICA L MOD E
Α andΒ Trigger
Selector
Circuit
Descri ption-7704A Service
In t h is mo d e, Q2090 is b iase d into
saturation by current
t h roug h C
R
1068 .
T he MF C h annel Switc h Signal (Display
R ig h
t)
is HI in t
h is mode, so α Hl is produced at p in 4 of
U 2404
.
T h
e
ano d
es of C R 1064 an d C R 1065 are grounded
to h ol d pin 14 of
U 2404 L O . U nd er th ese con d itions (pin 4
HI,
pin 14 LO), t he R IG H TVERT unit sup p lies t
h
e
trigger
signal .
LEF T VER T . Since only one b utton of t
he trigger
source switch
can
b e p resse d in at α time,
pressing LEF T
VER T opens t he contacts in t
h
e
VER T M OD E section of
t he trigger source switc
h
so pins
4 and 14 remain L O . As
indicate d by t h e in p ut/out
p ut table of F ig . 2-22, t h is causes
t h e
LEF TVER T unit to supply t he trigger signal .
F ig . 2-22
. I npu t/o u tp u t table for Α and Β
Trigge r Selector stages .
R IG H T VER T . In t
h e R IG H TVERT position of t
h
e
trigger sou rce switch , +5
volts is connecte d to R2093 of t h
e
voltage d ivider . T h is causes p in
4 of U 2404 to go ΗΙ . At t h e
same time, p in 14 is d isconnecte
d from its voltage source,
causing it to stay at α
L O level . U n d er t h ese input
con d itions, t he
R IG H T VERT unit su pp lies t he
trigger
out put signal .
T he Α an d Β Trigger
Selector stages d etermine w
h
ic
h
input signal p rovi d es t
h e trigger signal to t h e time-base units
as controlle d by t h e
trigger mo d e an d ADD signals from t
he
trigger selection
circuitry . R esistors R 2401, R 2402,
R
2421,
and R 2422 establis
h t h e in put resistance of t h is stage an
d
provide α loa d for t
h e trigger out p ut of t h e left and
rig h t
vertical plug-in
units . R esistors R 2403-
R 2404- R 2405 an d
R
2406-
R 2407- R2408 esta b lis h t h e op erating
levels for t h e
Α Trigger Selector ; R 2403-
R
2405 and
R 2406- R2407 set
t h e current gain for
eac h ch annel . R esistors
R 2423- R 2424-
R
2425 an
d R 2427- R 2428- R2429 establis
h
2- 2
7
VER TICA L
M OD E
switc h
p ositio n s
VER T M OD E
LEF T R IG HT
VER T
I
VER T
Ι LEF T
L
O ( L
eft
Verti-
cal)
Switc
h
es
f r
o
m
A
L
T
L O to HI, a nd
vice
ve rsa, at e nd
of each sweep
(b oth ; follows
dis p lay)
L O ( L
eft
HI ( R ig h t
ADD
L O at p i n 4 of
V
e r
tical)
Ι
V
e r
tical)
U 2404 a n d
U 2424 . HI at
pin
14' (b ot h ;
CHO
P
adde d alge b ra-
ically)
R IG HT
HI ( R
ig
h t Verti-
W
cal)

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English