Logic; Input/Output Conditions For Horizontal Logic; Functional Diagram Of Beam 1 Z-Axis Logic - Tektronix 7844 Instruction Manual

Theory of Operation-7844/R7844 Service
HORI ZONTAL
COMPARTMENT
CON DITI ONS
U285
A HORIZ-TIME BASE
HI
B HORIZ-AMPLI F I E R
A HORI Z-AMPLI F I E R
HI
B HORIZ-TlME BASE
ALL OTHER COMBINATIONS
Fig. 3- 1 0. Input/output conditions for Horizontal Logic Alternate
Switching.
Beam 1 Z-Axis Logic
The Beam 1 Z-Axis Logic stage produces output cur­
rents that determine the intensity of the beam 1 display. The
level of the beam 1 Z-axis output current is determined by
the BEAM 1 I NTENSITY control setting, by current added
for auxiliary Z-axis functions, or by an external signal ap­
plied to the Z-AXIS INPUT 1 connector. When an amplifier
unit is operating in the chop mode, the beam 1 display is
blanked by the chop blanking signal. A current-limiting cir­
cuit protects the crt from excessive beam intensity. I ntegrat­
ed circuit U335 provides beam 1 Z-Axis Logic and U31 5 and
Q304 provide beam 1 Auxiliary Z-Axis Logic. Refer to Fig. 3-
1 1 for a functional diagram.
Chop Blanking Z-Axis Logic.
blanking signal at U335 pin 6 disables the Z-axis output
current at U335 pin 8 during plug-in unit vertical chop
blanking. The beam 1 chop blanking signal is coupled from
U205 pin 4 directly to pin 6 of U335. Quiescently, the level at
pin 6 is HI so that the intensity current through pins 1 , 2, 9,
1 0, and 16 can pass to the output. However, during plug-in
unit vertical chop blanking, the level at pin 6 is LO and the
output current at pin 8 is blocked, which blanks the beam 1
crt display.
Mainframe Intensified
7844/R7844 is operating in an intensified mode, with a de­
laying time-base unit in the A HORIZ compartment and a
delayed time-base unit in the B HORIZ compartment, cur­
rent for the intensified zone is supplied from the BEAM 1
INTENSITY control to U335 pin 2. Current is added to the
beam 1 intensity current during the time that the delayed (B)
sweep runs. The delaying sweep time is indicated by a H I
level at U335 pin 1 4 ( A Gate) and the delayed sweep time is
3- 1 6
OUTPUT
PIN
8
H I LO
A
LO HI B
NO OUTPUT PULSE
1 676-83
( LO AT OUTPUT}
The beam 1 vertical chop
Z-Axis

Logic.

When the
A U X Z-AX IS
CHOP BLANKING
I N H I B I T
}
INTENSITY LIMIT
AUX Z-AXI S F ROM
V E RTICA L UNIT
EXTE R NAL Z-AX IS
D E LAY MODE CONTROL
HOR IZONTAL
BINARY (A O R B)
A GATE
B GATE
D ELAYI NG SW E E P
I NT E NSI F I E D
(DUAL T I M E BASE)
BEAM 1 I NTENSITY
Fig. 3- 1 1 . Functional diagram of Beam 1 Z-Axis LogiC (U33S).
indicated by a HI level at U335 pin 4 (8 Gate). The HI level at
U335 pin 5 indicates that the time-base unit in the A HORIZ
compartment is operating in the delaying mode. A LO level
at pin 1 5 (pin 1 5 is LO when the A HORIZ compartment has
been selected for display) routes current to pin 8 during the
time that the B Gate (pin 4) is H I . With this method of
supplying current for intensified sweep, the intensified cur­
rent increases as the BEAM 1 I NTENSITY control setting is
advanced to provide a proportional intensity increase in the
intensified zone as the overall beam 1 intensity increases.
The A Holdoff signal (from circuit board pin M) is coupled
through CR288 to U335 pin 2 to immediately terminate the
intensified zone at the end of A sweep.
Dual Time-Base Intensified Z-Axis LogiC.
horizontal Z-Axis Logic circuit provides the additional cur­
rent needed to intensify the delaying sweep of a dual time­
base unit (selected for display of beam 1 ) during the time
that the delayed sweep generator runs. Separate beam 1
auxiliary Z-axis amplifiers are provided for the dual time­
base units installed in the A HORIZ and B HORIZ
compartments.
Integrated circuits U31 5C and U31 5B form an emitter­
coupled current amplifier for the auxiliary Z-axis signal from
the A HORIZ compartment, and U31 5A and U31 5D form an
emitter-coupled current amplifier for the auxiliary Z-axis sig­
nal from the B HORIZ compartment. Only one amplifier will
1 0
U335
5
BEAM 1
BEAM 1
Z-AXIS
Z-AX IS
1 5 LOG I C
SIGNAL
1 4
4
1 6 76-84
The beam 1
R EV JUN 1 981