Tektronix 7704A User Manual

T he following discussions d
escribe the o
p
eration of the
Alternate
P ulse Generator stage in relation to the various
combinations of input con d itions shown in Fig . 2-7 Β .
1 . Α (ONLY) MODE
An Alternate P ulse is produce d at the en d of each
Α
sweep when the H
ORIZONTAL MODE switch is set to the
Α position .
2 .
Β (ONLY) MODE
In the
Β
position of
the H ORIZONTAL MODE switch,
an Alternate
P ulse
is pro
duced at the end of each Β sweep
( Α
time-base must be
in in d ep endent,
non-delayed
mode) .
3 .
ALT OR CHOP MODE
When the H ORIZONTAL MODE switch is set to ALT or
CHOP ( Α time-base unit must be in in d ependent,
non-delayed mo d
e),
an Alternate P ulse is produced at the
en d of each sweep . For example, an Alternate
Pulse
is
produced at the end of the Α sweep, then at the end of
the
Β sweep, again at the end of the
Α
sweep, etc .
Although
Alternate P ulses are pro d uced in the CHOP horizontal
mo d e, they are not use d in this instrument .
4 . DELAYED SWEEP ( Α
DELAYS Β )
When the Α
time-base unit is set for d elaye d operation,
the
operation of the Alternate P ulse Generator is changed
so an Alternate
P
ulse is produced only at the end of the Α
swee p , even
when the
HORIZONTAL
MODE switch is set
to Β . T his is necessary since the Α time-base
establishes the
amount of delay time for the Β time-base unit whenever it
is displaye d .
5 .
AMPLIFIER UNIT
IN
HORIZONTAL
COMPARTMENT
When an amplifier unit is installe d in either of the
horizontal plug-in compartments, the Alternate
P
ulse can
be p roduced only from
the remaining time-base unit . If
amplifier units
are installe d in both horizontal compart-
ments, an
Alternate P ulse is not pro du ce d since there are no
time-base units to pro duce α h oldoff p ulse .
Ζ -Axis Logic
T he Ζ -Axis L ogic stage p roduces an output
current
which sets the intensity of the d isplay on
the CRT . The
level of this output current is determined b y the setting of
the Α or Β I NTENSITY controls, by α current a dd e d to
provi d e an intensifie d zone on the
Α sweep for
d elayed-sweep operation, or b y an
external signal . The
input current from the Α and
Β I NTENSITY controls is
switche d so that the out p ut
current matches the h orizontal
Ο
d isplay .
The
Choppe d Blanking signals are applied to this
stage to block t he output current an d blank t he
CRT
display
for
vertical
an
d h
orizontal
chopping .
Figure 2-8 i d entifies the inputs to the Ζ -Axis L ogic IC,
U 2587 . This IC (integrated circuit) is current-driven at
all
inputs except pins 5 and 15 . The current at pins 1, .2, 9, and
16 is variable from zero to four milliamperes and is
determined
by
the applicable, current source
to control
the
output current at p in 8 .
Β INTENSITY
Α Intensified
Β Gate
Delay Mode Control
Horizontal an d
V ertical Chopped
Blanking
E xternal
and
A uxiliary Ζ -Axis
Α Gate
MF C hannel Switch Signal
(Display Β )
Α INTENSITY
Circuit Description -7704A
Service
F ig . 2-8 . In p ut and o utput pins
for
Ζ -Axis
Logic IC .
Ζ -Axis
Signal
T he Choppe d Blanking signal connected to p
ins 6
and
7
enables or d isables this stage to
control
all
output current .
Quiescently, the level at p ins 6 and 7 is HI so that
the
intensity current from p ins 1, 2, 9, an d 16 can pass to
the
output . H owever, pins 6 and 7 go
L O during Vertical
Choppe d Blanking or
H
orizontal
Cho
p
ped Blanking . This
b locks
the
output
current an d t he CRT is blanked . The
Vertical Chopped Blanking signal is connected d irectly to
U 2587 from p in 4 of U 2510 . The
H orizontal
Choppe
d
Blanking is connecte d to
U
2587
from p in 4 of U 2520
through
LR2523
an
d C R2524 . CR2524 is normally reverse
biased .
When the H orizontal Chopped Blanking level goes
LO, CR2524 is forward biase d to p roduce α corresponding
L O level at p ins 6 an d 7 of U 2573 .
The
Α I NTENSITY control sets the out p ut current level
when
the Α Gate at p in 14 is ΗΙ and the MF (Main Frame)
Channel Switch
Signal
at
pin 15 is L O . The Α I NTENSITY
current is b locked
whenever the Α Gate level goes L O
(in d icating that
the Α sweep is complete), or the MF
C hannel
Switch Signal goes ΗΙ (indicating that the Β sweep
is
being d isplayed) . The current from the Α I
NTENSITY
control
(see d iagram 1) is connected to pin 16 through
R2587 .
2- 1 3

Tektronix 7704A Specifications

General

Brand	Tektronix
Model	7704A
Category	Test Equipment
Language	English