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Tektronix 585 - Page 34

Tektronix 585
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Circuit
Description
—
Type
585
Fig.
4-2.
Operation
of
the
trigger
circuit.
As
the
triggering
signal
voltage
exceeds
the
predetermined
triggering
level,
a
sweep
begins.
able
for
instruments
before
Serial
No.
2585
as
Tektronix
Field
Modification
No.
040-275,
and
is
required
in
order
for
proper
operation
of
Plug-In
Units
with
numbers
above
Type
81.
See
your
local
Tektronix
Field
Engineer
for
details
and
availability.
Cathode-Ray
Tube
Six
pairs
of
distributed
vertical
deflection
plates
are
used
in
the
cathode-ray
tube.
This
arrangement
of
distributed
plates
permits
the
necessary
c
rt
sensitivity
while
at
the
same
time
reducing
objectionable
effects
of
capacitance
between
the
plates.
The
deflection
plate
lines
are
constructed
so
that
the
velocity
of
the
deflection
waveform
through
the
line
is
essentially
the
same
as
the
velocity
of
the
electrons
passing
through
the
plates.
TIME-BASE
A
TRIGGER
CIRCUIT
General
Triggering
signals
from
the
line,
TRIGGER
INPUT
con
nector,
and
Trigger
Pickoff
circuit
of
the
vertical
amplifier
can
be
individually
connected
to
the
input
of
the
Time-Base
A
Trigger
circuit.
The
triggering
signal
selected
by
the
TRIGGERING
SOURCE
switch
is
then
connected
to
the
control
grids
of
the
Trigger
Difference
Amplifier
stage
V24
and
V34.
The
Trigger
Difference
Amplifier
is
supplied
push-pull
signals
from
the
internal
Trigger
Pickoff
circuit,
but
single-
ended
signals
from
the
LINE
or
EXT.
sources.
Instruments
with
a
Vacuum
Tube
Trigger
Regen
erator
The
Trigger
Difference
Amplifier
is
used
to
control
the
operation
of
the
Trigger
Regenerator
multivibrator.
The
TRIGGERING
LEVEL
control
establishes
the
operating
point
of
the
Trigger
Difference
Amplifier
by
determining
the
d
c
voltage
applied
to
one
grid
of
the
amplifier.
By
controlling
the
operating
point
of
the
difference
amplifier
with
the
TRIGGERING
LEVEL
control
it
is
possible
to
determine
at
which
voltage
level
of
the
triggering
waveform,
triggering
occurs.
The
amplifier
triggering
pulses
from
the
difference
ampli
fier
are
applied
through
a
cathode
follower
to
the
input
of
the
trigger
multivibrator
circuit.
The
trigger
multivibrator
is
a
monostable
Schmitt
Trigger
Circuit
which
switches
when
the
output
of
the
difference
amplifier
reaches
a
certain
level.
When
the
multivibrator
switches,
an
output
pulse
is
applied
from
the
multivibrator
to
the
sweep
circuit.
This
pulse
is
relatively
constant
in
amplitude
regardless
of
the
amplitude
of
the
original
triggering
signal.
After
applica
tion
of
the
pulse
to
the
sweep
circuit,
the
multivibrator
resets
to
await
the
next
triggering
signal.
Instruments
with
a
Tunnel
Diode
Trigger
Regen
erator
The
Trigger
Difference
Amplifier
stage
is
used
to
control
the
operation
of
the
tunnel
diode
Trigger
Regenerator
cir
cuit.
The
TRIGGERING
LEVEL
control
establishes
the
oper
ating
point
of
the
Trigger
Difference
Amplifier
by
deter
mining
the
d
c
voltage
applied
to
one
of
its
grids.
By
con
trolling
the
operating
point
of
the
Trigger
Difference
Am
plifier
with
the
TRIGGERING
LEVEL
control
it
is
possible
to
determine
at
which
voltage
level
of
the
triggering
wave
form,
triggering
occurs.
(See
Figure
4-2).
Trigger
Difference
Amplifier
The
Trigger
Difference
Amplifier
is
essentially
a
current
control
of
the
tunnel
diode
Trigger
Regenerator
circuit.
As
the
plate
current
of
V34
increases
with
positive
going
grid
signals,
the
tunnel
diode
will
switch.
Trigger
Regenerator
The
tunnel
diode
Trigger
Regenerator
output
is
an
almost
rectangular
waveform
of
approximately
0.45
volt
peak-
to-peak.
It
is
d
c
coupled
to
the
base
of
the
Trigger
Ampli
fier
Q44
where
it
is
inverted
and
amplified.
The
amplified
4-4

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