Tektronix 7704A User Manual

Circuit Description
-7704A
Service
Display
R ight
Command
A LT Mode (vert)
Input
All
vertical m odes except ALT,
provides sweep-
slaving for non-delayed dual-sweep
o peration .
Output
Φ = Has no
effect in t his case .
η +1 = If out p ut
is LO prior to LO I it goes HI, a
nd
vice
versa .
1 Actuated by negative-g oi ng e d ge
.
2 R epetition rate one-half
Display R ight Command
rate .
Alternate
Drive
Clock Generator
F ig . 2-14 .
(
Α
)
Logic diagram for Plug-in
Binary stage ;
(
Β
)
Table of input/output combinations .
P art of integrate d
circuit U2510, along with t he external
components shown in
Fig . 2-15 Α , make up the
Clock
Generator stage .
R
1,
Q1, Q2, and Q3 represent an
e q uivalent circuit
within U 2510 . The output at pin 15
is α
free-running
timing (Clock) signal use d to synchronize
the
vertical, h orizontal,
and
p
lug-in chopping mo d es .
The frequency of
the Clock signal is either 200
k ilohertz
or two megahertz,
d epend ing on the position of
the internal
Chop
Frequency switch S2510 . The 200-kilohertz output
is
p rovi ded for
other systems using the Α 7704
Acquisition
U nit (the b ottom
half of the 7704 Α ) . For normal
operation
of
the 7704 Α , t he Chop Fre q uency switch s
hould be left in
the 2-MHz p osition .
2- 20
When the internal Chop
Frequency switch is in the
200-kHz position,
the
stage
operates as follows : At time T o
(see Fig . 2-15
Β ),
t
he collector current through Q2 is
prod ucing α voltage drop
across R 1 to cut off Q1 . Since
there is no current
through Q1, C2510 and C2511 b egin to
charge towar d s -15
volts through R2510-R2511 .
This
causes the emitter of
Q1 to gra d ually go negative
until
it
is
about 0 .6 volt
more negative than the base . At this p
oint
( Τ 1 on Fig .
2-15 Β ), Q1 is forwar d b iase d into
conduction
and its emitter rapi d
ly goes positive . Since the charge on
C2510-C2511 cannot
change instantaneously, the su d
den
change in voltage at
the emitter of Q1 p ulls the emitter of
Q2 p ositive also, to
reverse-bias it into cutoff
. When the
current through
Q2 stops, its collector rises to p
roduce α
positive output
level at pin 14 (time Τ 1 ) .
Ο
LO
LO 1 η
+1 2
A LT
V ertical Mode
HI LO
Φ LO
Channel 1 displayed
ξ
HI
HI Φ HI C
hannel 2 displayed

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English