Circuit Description—434
similar to tha t described fo r the Erase M ultivibrator. When
either ENHANCE switch (S90C or S92C) is pushed in,
Q1245 has a conduction path to ground through R1245.
Q1245 saturates and the low voltage-level at the collector
of Q1245 keeps Q1246 turned o ff. The negative-going
portion of the Enhance Trigger pulse from the Sweep
circu it is coupled through C l240 to switch the Enhance
M ultivibrator. Q1245 turns o ff and Q1246 turns on. The
collector of Q1246 snaps down to about —15 volts
producing a negative-going step which is coupled through
C l246, and turns o ff CR1245. The length of time that the
m ultivibrator remains in this state, and thus the pulse
w id th , is determined by the values of R1244 and C1246.
The setting of the ENHANCE LE V EL control, R92, deter
mines the amplitude of the pulse which is applied to the
feedback am plifier summing point.
1 integrate
The second fast w ritin g technique to be discussed is
integration. In this mode of operation, the flood gun beam
is interrupted mom entarily, allowing the w riting gun beam
to sum small amounts of charge for successive sweeps so
th at when the flood electrons are again turned on, the
scanned target area shifts to the stored state. This is
accomplished by pressing the IN TEG R ATE switch, S94,
which disconnects the flood gun cathodes. This also
connects —75 volts to the error signal input term inal of the
high-voltage regulator circu it through R960 to sh ift the
high voltage slightly, correcting fo r the deflection sensi
tiv ity changes that occur when the flood guns are turned
o ff. Releasing the INTE G RATE switch, then, allows the
display to shift to the stored state.
3-29
To Next Page
Loading...
Need help?
General
