Tektronix 5103N

SECTION
3
CIRCUIT
DESCRIPTION
5103N
Change
information,
if
any,
affecting this section will be found
at
the rear of this
manual.
Introduction
This section
of the
manual
contains an
electrical
description of the circuits in the 5103N Power
Supply/
Amplifier
unit, and
discusses their relationship
to the other
instruments comprising the Oscilloscope
System. An
overall
block diagram of the unit and
complete schematics
are
given on pullout pages
at
the back of this
manual.
BLOCK DIAGRAM
DESCRIPTION
Vertical signals
to be displayed on the
cathode-ray
tube
are applied
to the Interface circuit
from
both
vertical
plug-
in compartments. With single-beam
display units, the
Inter-
face circuit determines
whether the signal from
the left
and/or right vertical unit
is
displayed;
with dual-beam
units,
the
Interface circuit establishes the proper
routing
to asso-
ciate the left
vertical plug-in signal with the
upper
CRT
beam and right vertical plug-in
signal with the lower
CRT
beam. The Vertical Amplifier
circuit provides
intermediate
amplification between
the vertical plug-in
units and
the
deflection amplifiers
in the display unit.
Time-base and
external signals for horizontal display
on
the
CRT
are
connected to the
Interface
circuit
from
the
horizontal plug-in compartment. The
Horizontal
Amplifier
circuit provides
intermediate amplification between the
horizontal plug-in unit
and the
deflection amplifier
in the
display
unit.
Additionally, the
Interface circuit provides an
inter-
connection
of
logic
levels, time-base triggering signals,
display-related signals, and
power-supply voltages between
the plug-in units and the
display
unit.
The
Low-Voltage
Regulator
circuits provide the voltage
necessary
for operation
of
the
oscilloscope system. These
voltages are
connected to all circuits
within the instrument.
Also
included in
this circuit is the
Calibrator, which
pro-
duces
a
square-wave output
with accurate amplitude
at a
repetition rate
of twice the power-line frequency. This out-
put
signal is useful
for calibration and
probe compensation,
and is available at
the front
panel of the display unit.
INTERFACE
General
The Interface circuit provides
an
interconnection
of
signals, logic levels,
and power-supply
voltages between
plug-in
units and the oscilloscope
mainframe.
It incorpo-
rates
circuits that determine
the vertical
display
mode and
amplify the
vertical and horizontal
display
signals.
Func-
tions
of
interconnections
not
discussed
are labelled
on the
I nterface
diagram.
Clock
Generator
The Clock
Generator
stage
produces
a 200-kilohertz
timing
signal (clock) for
chopping
between
vertical
plug-ins
and amplifier
channels
within the
plug-ins.
This
circuit
consists of
Q620,
Q626,
and their
associated
passive com-
ponents,
which are
connected
as
a multivibrator.
When the
multivibrator
receives
a chop
actuate level
(+5 volts), it free
runs
at a 200-kilohertz
rate.
(The chop
actuate level is
routed
through
the
vertical
plug-ins
to the
time-base unit,
and
is present
at
contact
A20
of
J603 when
a
multi-trace
display
is required
and
the
time-base
Display
switch
is set to
Chop.)
The chop
actuate level
also
disables
Q630,
locking
out
alternate-drive
pulses.
The
Clock
Generator
has two
outputs;
one is
sent to the
Countdown
circuit
as
a
timing
signal, and
the other
is
sent to the
CRT circuit
in the
dis-
play
unit
to blank the
chop-switching
transients.
Countdown
Circuit
The
Countdown
produces the
display
switching
signal
for
both
the Alternate
and Chopped
switching
modes.
This
circuit
is composed of
U640
and its
discrete
passive compo-
nents, which are
connected
as a pair of
RS flip-flops.
Each
flip-flop
is
a divide-by-two
counter,
and the first
one drives
the
second. The Countdown
Circuit
is activated by
a
negative-going
transition,
which can
come from either the
Clock
Generator or
from the
time-base
plug-in unit
via
grounded-base
amplifier
Q630.
The
Clock
Generator input
results in
chopped-mode
vertical switching.
The
input
from
the time-base
unit coincides
with the
end of each sweep,
and
results in alternate-mode
vertical
switching. The
output
from
the divide-by-two
portion of the
Countdown
Circuit
(U640A-U640B) is sent
via contacts
B21
of
J601
and
J602
to the channel-switching
circuits
incorporated within dual-
trace vertical plug-in
units. The
outputs
from
the divide-by-
3-1