Tektronix 7613 User Manual

STORAGE BOARD CIRCUITRY
The Cathode-Ray tube of the 7613 is a standard
transmission halftone storage tube. The collector electrode
is a coarse mesh which accelerates electrons toward the
target area. The target is a fine mesh with a highly insulative
dielectric layer deposited on it. It is in the dielectric layer
that storage occurs. The flood guns cover the entire storage
target with a continuous stream of low velocity electrons;
these electrons are prevented from reaching the phosphor
screen unless a display has been written on the storage
target.
The collimation bands are used as a lens which
uniformly distributes flood-gun electrons over the storage
target area. Adjustment R1531 controls the output voltage
of the collimation amplifier (1538 and Q1539) used for
the first two bands. In the non-store mode, the collimation
bands have no control over the CRT. Adjustment R1521
controls the emitter-followers output that controls the
third collimation band. Transistor Q1512 and voltage
divider R1510 and R1511 establishes the collector voltage
for the CRT. (See storage basic block diagram Fig. 3-38.)
Switching from the non-store mode to the store mode is
done by grounding the store line. This enables the ERASE
switch, REMOTE ERASE switch, and the SAVE switch.
Circuit Description—7613/R7613 Service
Transistor Q1329 is biased on in the non-store mode. The
output of 01329 is coupled to the base of Q1331, the
input to the Erase Timing Generator. When transistor
Q1331 is turned off, an erase cycle is started. In the store
mode, transistor 01329 is biased off and transistor Q1331
is biased on. When changing modes from non-storage to
storage operation, an erase cycle is generated automatically.
When the REMOTE ERASE switch is pressed, it grounds
one side of capacitor C1318. Capacitor C1318 discharges in
to the base circuitry of 01331, turning it off momentarily.
When the ERASE switch is pressed, 1331 is biased off so
that repetitive erase cycles can occur.
VARIABLE PERSISTENCE AND
SAVE CIRCUITRY
Transistors 01373 and Q1378 form a switch that allows
either the PERSISTENCE control or the SAVETIME
control to control the storage operation. Transistor 01373
is on in the store mode without save. Transistor Q1378 is
biased off and 01380 is biased on. This allows the collector
circuit of Q1380 to control the storage operation. Tran-
sistor Q1378 is turned on when resistor R1371 in the base
circuit of 01373 is grounded by the SAVE switch. This
lowers the emitter voltage, allowing 01378 to turn on and
Q1373 to turn off. When transistor 01373 turns off,
Q1387 turns on, allowing the collector circuit of Q1387 to
control the storage operation. See Fig. 3-39.
+50
SAVE/STORE
+15
PERSISTENCE- _~
+5
t|
Q1395
a1409,
Fig. 3-39. Variable Persistence and Save switching circuit.
3-51
7613

Tektronix 7613 Specifications

General

Brand	Tektronix
Model	7613
Category	Test Equipment
Language	English