Circuit
Description
—
Type
3B5
unit
is connected
to
this
unit
through
terminal
3
of
the
inter
connecting
plug
and
the
interconnecting
cables
in
the
indi
cator
oscilloscope.
The
network
D601-D602-R601-R602-R603-
C602-C603-C604
eliminates
all
signals
at
the
base
of
Q604
except
the
seek
command
to
prevent
a
false
seek
command
to
the
Seek
Circuit. A
remote
seek
command
from
the
ampli
fier
unit
turns
on
Q604
and its
collector
rises
positive to about
zero
volts.
Likewise,
the
front-panel
seek command
or
the
remote
seek
command
through J30
raises
the
circuit
potential
to
zero
volts.
The
seek command
may
either
be
momentary
or
it
may
be
a
continuous
seek
command.
The
seek com
mand
is
connected
to
the
base of
Q615
to
produce
the
seek
mono
pulse
and
to
the Operating
Mode
Power
circuit
through
D605
(see
Seek
Mode
Control
discussion)
to
switch
the
instrument
to
the
Seek
Mode
of
operation.
Q615
and
Q625 are
connected
as an
AC-coupled
multi
vibrator.
Quiescently, Q615
is
held
on by
the negative
potential
at
its
base established
by
the
—
12.2
volt
level
at
the collector of Q604
(no seek
command
applied).
The
base
of
Q625
is
clamped
at
about
+
0.5
volts
by
D619 and
Q625
is
held
off.
When
a
seek
command
is
received,
the
base
of
Q615
rises
positive
and
it
turns
off.
Its
collector
goes
nega
tive
toward
—
100
volts
and
is
clamped
when
it
reaches
about
—
12
volts
by
D614.
C616
begins
to
charge
and
this
charge
current
flows
through
R616
to
pull
the
base
of
Q625
negative
and
turn
it
on.
The
collector
of Q625
rises
positive
to
produce
the
seek
mono pulse.
This
pulse
is connected
to
the
Counter
Circuit,
Trigger
Latch
Circuit
and
the
Advance
Gate
stage. It also
provides
a
sweep
reset
pulse
to
the
Sweep
Generator circuit
through
C629
and
D629.
The circuit
remains
in
this
condition
until
C616
is fully
charged. Then,
the
current
through
R616
returns
to
its
quies
cent
level
and
Q625
is
turned
off again.
Its
collector
goes
negative
to
about
—
8
volts
to
end
the
seek
mono pulse. This
negative
change is
coupled
back
to
the
base
of
Q615
through
R626-R627-C627.
If
the
seek
command
has
ended,
this
feedback
has
no
effect
on
circuit
operation.
However,
if
a
seek
command
still
holds
the
base
of
Q615
near zero
volts,
this
feedback
pulls
the
base
of
Q615 negative
enough
to
turn
it
on again and
produce
another
seek
mono pulse.
As
long
as
a
seek
command
is
applied, Q615
and
Q625
act
as a
free-running
multivibrator.
Trigger
Latch
Circuit
Q634
operates
in
conjunction
with
Q54
in
the
Trigger
Circuit
to
provide
auto triggering
if
the
front-panel controls
are incorrectly set
or
a trigger signal is
not
applied
(Seek
Mode
operation
only).
Full
operation
of this
circuit
is
explained
under
Trigger
Latch
Circuit
in
the
Sweep
Trigger
discussion
Advance
Gate
The
Advance
Gate
stage
produces
an
output
level
which
either
locks
out
or
enables
the
Advance
Pulse
Generator
and
the
Advance
Pulse
Output
stage.
For
Manual
Mode
operation,
the
Advance
Gate output level
is
held
at
—
12
volts
by
Manual
Power
applied
to
the base of
Q643
through
D644.
This holds
both Q665 and Q684
reverse
biased
to
lock
out
any advance
pulses. In
the
Seek
Mode
of
opera
tion,
the
output
level from
the
Advance
Gate
depends
upon
the
input
levels.
D640
and
D641 comprise
an
“and" gate
for
the
"1
”
multiplier
and
0.1
μ
s
decade
(h)
logic levels.
When
both of
these
logic
levels
are —12
volts,
the
base
of
the
Advance
Gate
stage
goes negative
and succeeding
advance
pulses
are
locked
out.
This
condition
is
met
only
in
the
0.1
microsecond sweep
rate
when
the
“1"
logic con
nected
to
D640
and
the 0.1
μ
s
logic
connected
to
D641
are
both
at
—12
volts.
Current
then flows
through
R641,
D642
and
R643
and
the
base
of Q643
goes
negative.
This lock-out
action
prevents the
Counter
Circuit
from
returning
to
the
5
s
sweep
rate
on
fast
signals.
When
a
seek
mono
pulse
is
received
at
the
base
of Q643,
its
emitter
rises
positive
to
about zero
volts.
The
duration
of
the
output
pulse
at the
collector
is
the
same
as
the
dura
tion
of
the
seek
mono
pulse
at
the
base
unless
the 0.1
micro
second
sweep
rate
is
reached.
This
positive
output
level
enables
the
Advance
Pulse
Generator
and
the
Advance
Pulse
Output stages
to allow
advance
and
sweep
reset
pulses
to
be
produced.
Window
Gate and
Advance
Pulse
Generator
The
Window Gate
circuit
turns
on
the
Advance
Pulse
Generator
circuit
to
produce
advance
pulses
for
the
Counter
Circuit. When
an
Advance
Gate
enable
pulse
is
applied
to
the
emitter
of
Q665
through
D666
and
D665
(only
in Seek
Mode
with
seek
command
applied), its
emitter
level
rises
to
about
—
2.5
volts
as
set
by
D668
and
zener diode
D669.
Therefore,
the
base
of
Q665
must
go
below
about
—
3.0
volts
before Q665
can
be
biased
on.
Trigger
pulses from
the
Seek
Circuit
Driver
stage
in
the
Sweep
Trigger circuit
are
con
nected
to
the
base
of
Q665
through
T660
and
D661.
How
ever,
these
negative-going
trigger
pulses
are only
about
1.5
volts
in
amplitude so
they
do
not
turn Q665
on.
An
addi
tional
negative
level
must
be
provided
by
the
collector
level
of
Q664
to
turn Q665
on.
The
time
duration
of
this
negative
window-gate
signal
from
Q664
is
controlled
by
the
CYCLES/
SWEEP
adjustment,
R650,
to
determine
the
number
of
cycles
in
the
CRT
display.
Circuit
operation
is
as
follows:
the
sawtooth
produced
by
the
Sweep
Generator
circuit
is connected
to
the
base
of
Q653
through
R186.
The
bias
level
of
Q653 is
set
by
the
sweep
gate
connected
to
the
base
through
R650
and
R651
(only
during
a
sweep).
This
bias
level
can
be
adjusted
by
the
CYCLES/SWEEP
adjustment,
R650; the setting
of
R650
determines
the
amount
that
the
sawtooth
must
run
up
before
it
turns
Q653
on.
At
the
start
of
the
sweep,
both
Q653
and
Q664
are
biased
off.
The
sweep gate signal also
provides
the
collector
supply
for Q664.
Since
Q664
is
biased
off
at
the
start
of
the
sweep,
its
collector
goes
negative
toward
—
6
volts
and
is
clamped
at
about
—2.5
volts
by
divider
R657-R658
and
D657.
This collector
level allows
the
trigger
pulses
to
turn
on
Q665.
However, when
the
sawtooth
over
comes
the
bias
level
at
the
base
of
Q653
as set by
R650,
Q653
turns
on and
its
collector
goes
negative.
D655
switches
to
its
high-voltage
state
and
Q664
turns
on
very
rapidly.
The
collector
of
Q664
rises
to
about zero
volts
to
end
the
window-gate
signal. This locks out
any
further
trigger
pulses
at
the
base
of
Q665.
At
the
start
of
each
seek
cycle,
the
sweep
rate
is reset
to
5
seconds/division
by
the
seek
mono
pulse to
the
Counter
Circuit
and
the
sweep
is
reset
to
the
left
side
of
the
graticule
by
the sweep
reset
pulse
produced
by
the
Advance
Pulse
Generator
stage.
The
sawtooth
at
the
base
of
Q653
starts
3-36
Summary of Contents for 3B5
Page 4: ...Fig 1 1 Type 3B5 Automatic Programmable Time Base unit Type 3B5...
Page 15: ...Operating Instructions Type 3B5 TYPE 3B5 CONTROL SET UP CHART Fig 2 2 Control set up chart 2 7...
Page 48: ...CO I o Fig 3 13 Delay and Timing Circuit logic block diagram Circuit Description Type 3B5...
Page 61: ...GO i GO GO Fig 3 22 Seek Ciicuit Logic block diagram Circuit Description Type 3B5...
Page 70: ...u k KJ Fig 3 29 Circuit conditions for Manual Mode operation Circuit Description Type 3B5...
Page 71: ...w K w Fig 3 30 Circuit conditions for Seek Mode operation Circuit Description Type 3B5...
Page 72: ...w I u U Fig 3 31 Circuit condition for External Mode operation Circuit Description Type 3B5...
Page 88: ...Maintenance Type 3B5 Fig 4 9 Location of components on Logic Card 4 14...
Page 89: ...u Oi Fig 4 10 Location of components on Counter Card Maintenance Type 3B5...
Page 92: ...NOTES I...
Page 104: ...NOTES...
Page 106: ...Calibration Type 3B5 Fig 6 1 Recommended calibration equipment...
Page 160: ......
Page 176: ...J400 RtADOUT BOARD 3B5 PLUG IN A READOUT...
Page 182: ...397 R E A D O U T B O A R D 10 6b READOUT BOARD...
Page 184: ...FIG 1 FRONT SWITCHES TYPE 3B5 AUTOMATIC PROGRAMMABLE TIME BASE...
Page 185: ...FIG 2 CHASSIS REAR 3 GS to TYPE 3B5 AUTOMATIC PROGRAMMABLE TIME BASE...
Page 186: ...OPTIONAL ACCESSORIES...
