125
from
the
output
of
the
600
ms
timer
{D221
1/pin 1
1). At the
end
of
the
time-base
sweep
the
clear
input
(pin
4)
becomes
high
and the
flip-flop
comes
into
the
reset
condition:
output
Q
(pin
1) becomes
low.
QUADRUPLE
BILATERAL
SWITCHES
D2401,
D2402
and D2403
Each
integrated
circuit
contains
four
analogue
switches
(transmission
gates).
Each
switch
has two
input/output
pins
and
an "active
when
high"
control
input.
A high
level
on this
control
results
in
a low
impedance
bidirectional
path
between
the
two
matching
input/output
pins.
A low
level
on
the
control input
results
in
a high
impedance
path
between
the two
matching
input/output
pins.
The
following
inputs/outputs
and
control
pins are
associated:
—
Pin
13
controls
the transmission
gate
between
pins
1
and 2.
—
Pin
5 controls
the
transmission
gate between
pins
3 and 4.
—
Pin
6 controls
the transmission
gate between
pins
8 and 9.
—
Pin
1
2
controls
the
transmission
gate between
pins 10
and 11.
The
transmission
gates are
used for
applying
the appropriate
signal
at the right
moment
to the inputs
of the
amplifiers
that
drive the
storage
electrodes
of the c.r.t.
The
control inputs
of
D2401,
D2402 and D2403
are driven
by the storage logic.
When such
a control
input
is activated
(high)
the signal at
the input of
the gate is
switched
through the input
of the relevant
amplifier. This
input
signal
can be adjusted
in
order
to regulate
the
amplifier output
voltage.
FAST
MESH
AMPLIFIER
The fast
mesh
amplifier
comprises
transistors V2402,
V2403 operating
as a differential
input amplifier.
The
collector of
V2403 is
direct-coupled
to V2408, which drives
the complementary
output transistors
V2404
and
V2407.
Feedback
is provided
by resistor
R2454.
When no
input signals
are present,
the input
to V2402
is
provided
by a
-T5.6
V line and
the output potential
to the fast
mesh
G1 1 on R2449
is
constant at -H
40
V.
The amplifier
output is
controlled by
the preparatory
pulses and by
the image transfer
signal. When
preparatory
pulses are
received the
output is
switched
between -H40 V and
a value that
is adjustable
between 0 V
and
+15
V.
During the
image
transfer, the
output voltage
becomes a little lower;
it
is
adjustable
between
—1
V and
+15
V.
FRONTMESH
AMPLIFIER
The front
mesh
amplifier consists
of input transistors
V2458, V2431 and
the alternative
output transistor pairs
V2426, V2427
and V2421,
V2422 (each
pair is series-connected for high-voltage
switching).
When input transistor
V2458 is
conducting
(see
WRITE
and
FAST
mode descriptions),
the
V2431 also conducts.
The
collector potential of
V2431 falls
and switches
off V2426, V2427.
Diodes V2423, V2424 are blocked
and output
transistors V2421,
V2422 now
conduct to connect the front
mesh G12
to
+500
V.
When input transistor
V2458
is non-conducting, V2431 is
also switched off. The
increase in its
collector voltage
results in
output transistors
V2426, V2427
conducting and V2421, V2422
are
switched off. The front
mesh
is now
connected
via output transistor
pair V2426, V2427
to
the
voltage on the
output of the front
mesh
preamplifier. This
preamplifier
comprises transistors V2414,
V2416,
V2418 and the output
complementary
pair,
V2412, V2413.
FLOOD
GUN ACCELERATOR
AMPLIFIER
The flood
gun
amplifier consists of
a
differential
pair V2437,
V2438, the collector output
of V2438 being
direct-coupled
to the base of driver
V2442.
In turn, the
collector of this transistor
is direct-coupled
to the base of
output transistor V2439.
Feedback is
provided
by
resistor
R2512.
In
the various modes,
the output from R2504
to the flood gun accelerator,
FGA, can
be switched to one of
three levels
depending
on the inputs,
as
follows:
a. With no input
signal the
base of V2437
assumes a slight
positive potential
determined
by the feedback
resistor R2512.
In
this
condition,
the output
to the FGA is
+20
V.
b. When
the input
to V2437
is earthed
by the bilateral
input
switch D2401
(pin 4 to pin
3)
then V2437
conducts
further and
tends
to switch off
V2438
and, in turn,
V2442.
The collector
of V2242
goes positive
and
this
increase
in potential
applied
to the
base of
output transistor
V2439
causes it
to conduct
heavily.
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