Tektronix 7834

Transistors 03321-03323-03330
compose an inverting
feedback amplifier . The gain of
the stage is about 2, as
determined by the ratio of feedback
resistor R3328 to the
input resistance (made up of R3321
and either R192 or
R 193 depending on which sawtooth
source is selected)
.
RC
network R3330-C3320 provides
frequency-response stabili-
zation for this stage .
Gate
Amplifier
The + GATE OUT signal is selected from
three input gate
signals by the Gate Selector switch
S3340 . In the A and B
positions a positive gate signal from the
selected horizontal
compartment is connected to the base of
03351, and the
base of 03353 is connected to ground
. Before a gate occurs,
03351 is biased off and 03353
is conducting, its collector
potential is low enough to
cut off 03361 . When a gate
occurs, it is coupled to
the emitter of 03353, cutting it
off .
The current through
R3358 now flows through 03361 to
produce the
+
GATE
OUT .
In the DLY'D position, the base of 03351
is connected to
ground . The other section of the Gate Selector
switch opens
to
allow the negative-going Delayed Gate
signal from the
delaying time-base unit to reach the base
of 03353 . When a
gate occurs, 03353 is cut off,
producing a positive-going
signal at the + GATE OUT connector,
as in the case of the
A and B Sweep Gates .
READOUT
SYSTEM
The Readout System
provides an alpha-numeric display of
information encoded by the
plug-in units . This display is
presented on the crt, and is written by
the crt beam, on a
time-shared basis with the analog
waveform display .
The following terms
are used to describe the Readout
System :
Character-A single
number, letter, or symbol displayed
on the crt,
either alone or in combination with
other
characters .
Word---A group of related characters . In the
Readout
System, a word can consist of up to
10 characters .
Frame--A display of all
words for a given operating mode
and plug-in
combination . Up to 8 words can be displayed
in
one frame . Figure 3-26 shows the position of
each
word
in a complete frame .
Column-One of the vertical
lines in the Character Selec-
tion Matrix (see Fig . 3-27) .
Columns C-O (column zero)
through C-10 (column 10) can be
addressed by the
system .
Row--One of the horizontal
lines in the Character Selec-
tion matrix . Rows R-1 (row 1)
through R-10 (row 10)
and R-14 (row 14) can be
addressed by the system .
Time-Slot-A location in a
pulse train . In the Readout
System, the pulse train
consists of 10 negative-going
pulses . Each time-slot pulse
is assigned a number between
1 and 10 . For example, the first
time-slot is TS-1 .
Time-Multiplexing---Transmission
of data from two or
more sources over a common
path by using different
time intervals for different signals
.
Display Format
Up to 8 words of readout
information can be displayed
on
the crt . The
position of each word is fixed and is
directly
related to
the plug-in unit from which it originated
. Figure
3-26 shows
the area of the graticule where
the readout from
each
plug-in unit is displayed . Notice that
Channel 1 of
each
plug-in unit is displayed within
the top division of the
crt, and Channel 2 is displayed
directly below within the
bottom division . Figure 3-28
shows a typical display where
only Channel 2 of the Right Vertical
and B Horizontal
units
is selected for display .
Each word in
the readout display can contain up to
10
characters, although the
typical display will contain
between
2 and 7 characters per word
. The characters are selected
from the Character
Selection Matrix shown in Figure
3-27 .
In addition, 12 operational
addresses are provided
for spe-
cial instructions to the
Readout System . The unused
LEFT VERT

RIGHT VERT
CHANNEL1 CHANNEL1
4_~ . .I,-,l. .
Theory of Operation-7834
A HORIZ
CHANNEL1
B HORIZ
CHANNEL1
CHANNEL 2
LEFTVERT

I

CHAN ELY I

CHANNEL 2
AHORIZ

I

CHANNEL
2
1987-4
Figure 3-26 . Location of readout display on
the crt identifying the
or'iginafing
plug-in and channel .
3- 35