Tektronix 7834

Storage Lockout
This stage, comprised of 02588, U2552D, CR2551,
CR2552,
CR2553, CR2554, and CR2555,
develops the Storage Lock-
out signal when the storage system
is unprepared to produce
a stored display . The Storage Lockout signal
inhibits the
time-base unit(s), the Storage Sweep Gate, the Remote
Storage Gate and blanks the crt . The 5 diodes connected
to the base of Q2588 form a 5 input OR gate .
A HI level
applied to the anode of any one of
these 5 diodes will pro-
duce a HI Storage Lockout signal at the
emitter
of
Q2588
(pins 11 and 12 of U2552D must both be LO for a HI to be
applied to the anode of CR2553)
.
Readout Control Logic
This stage provides two signals to the Readout
System : the
Readout Gate and the Gated Readout
Intensity . The Read-
out Gate signal is generated by
U2608A, B, and D, U2565B
and
D,
and S2610 . When S2610 is
set
to
the FREE RUN
position the Readout Gate is
HI, which allows the Readout
System to operate continuously in a
free-running manner .
When S2610 is set to the
GATED position, the state of the
Readout Gate depends
upon the end-of-sweep pulse from
U2592C
(see
Transfer and Multi stage) and the setting of
the Storage Mode Switch . In the NON-STORE or the VAR
PERSIST mode, the Readout Gate duplicates the end-of-
sweep pulses causing the Readout System to produce one
complete frame (eight words) at the end of each sweep .
In
the FAST VAR PERSIST mode a Readout Gate
is also pro-
duced
at
the end
of
each sweep . However, the Gated Read-
out Intensity (explained below) inhibits the Readout
System
so
it will
not write on the Fast Mesh . Instead,
R2608 and C2608 differentiate
the W signal and couple the
rising edge into
the Readout Gate circuit to initiate one
complete frame of readout at the end of each transfer
operation .
In BISTABLE and FAST BISTABLE modes the writing
speed of the Storage Target is too low to store a single
frame of readout . For this reason, the Readout System free
runs at the end of a sweep until the next Erase pulse occurs .
The Readout Gate goes LO at the initiation of the Erase
pulse since Mufti is H I and applied to pin 2 of U2608 . The
MULTI signal goes LO at the first end-of-sweep pulse,
causing the Readout Gate signal to go H I .
The Gated Readout Intensity is an analog
current signal
which controls the crt intensity during the readout display .
At zero current it also inhibits the Readout
System . When
02688 is
on, the Readout Intensity control adjusts this
current to control the brightness of the readout display .
When Q2688 is off, the current is zero, turning off the read-
out . Transistor 02688 is off during the Erase and Multi
Trace cycles (X or W HI) and in the fast storage modes up
to the end of the transfer operation
(W HI) . Additionally,
02686 is turned on
when the Save signal is H I . The delay of
R2686 and C2686 allows
the readout to run for a suffi-
cient time, upon entering the SAVE mode, to store
the
readout display in the Bistable or Fast Bistable
modes .
When the Save mode is entered during a
Multi Trace cycle,
CR2686 holds C2686 discharged
until the end of the X
pulse to allow the readout to be
stored .
Flood Gun Cathode Driver
Theory of Operation-7834
Transistors 03054 and 03064
comprise the FGK (Flood
Gun Cathode) Driver stage . The output
of this stage has
two states . When 03064 is saturated, the
FGK
is at
ground
potential and the flood guns are on . When
03064 is off,
CR3066 clamps the FGK at approximately
1 volt above the
FGA (Flood Gun Anode) and the flood
guns are off . The
flood guns are on continuously in all
display modes except
Save . In the Save mode, the flood guns
are modulated by
the Save Intensity signal, turning the
flood guns on and off
at duty cycle that is determined by
the setting of the front-
panel SAVE INTENSITY control
. Resistor R3052 and
capacitor C3053 delay the
turning off of the flood guns
when the Save signal switches
HI, allowing the Readout
System to turn off before
flood gun modulation begins .
The Power On signal overrides all other inputs,
turning the
flood guns off when the 7834 power is switched
on or off .
This prevents spurious erasure of the stored display
due to
rapid changes in supply voltages applied to
the storage
circuits .
Collimation Electrode #1 and Flood Gun Anode
Driver
This stage
consists
of a
current input operational amplifier,
03022 and 03026, and an emitter follower 03048 driven
by a
resistive divider . The inverting input (base of 03022)
operates at
zero volts ; R3026 is the feedback resistor . The
input current
signal is provided by the Collector and Colli-
mation Electrode Decoder stage . This amplifier drives the
Flood Gun Anode (FGA) through R3027 . The drive for
Collimation Electrode
#1
(CE1) is taken from the emitter
of 03048 which drives the output of the Flood Gun Anode
Driver through resistive divider R3045, R3046, R3047 .
Collimation Electrode Drivers #2, #3, and #4
These driver stages are operational amplifiers similar to that
discussed above for the FGA Driver . Transistors 02992 and
02996 comprise the driver for CE2, 02972-02976 for
CE3, and 02942-02946 for CE4 . Note that the output
resistor for the CE2 Driver, R2978, is contained within
the
feedback loop of this amplifier to provide a
lower effective
output impedance .
Collector Mesh Driver
This stage consisting of 02914, 02918, and 02924 is an
operational amplifier similar to those just discussed for the
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