www.SteamPoweredRadio.Com
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Operation
the CAL position. This control can be used however
to
reduce the gain
of
the relevant amplifier and
obtain any intermediate sensitivity between the
calibrated switched ranges. To set
to
any particular
calibrated sensitivity, the actual variation from the
calibrated range can be set
by
viewing the CAL
I
Volto/pon
the0.IV/cm
or0
.2
V/cm ranges.
If
the
VAR SENS control
is
not moved, the sensitivity will
differ from the calibrated value by approximately the
same proportion on all settings
of
the VOLTS/CM
switch.
To minimi
ze
pick-up at sensitive settings, it
is
essen-
tial
to
ensure that the ground lead connection
is
near
to
the signal point.
5. For vertical movement
of
the trace, adjust the Y shift
controls (identified by the vertical arrows).
6. Any trace movement under no-signal conditions,
when the setting
of
the VOLTS/DIV switch
is
altered,
can be overcome by adjustment
of
the relevant preset
front panel balance control.
This control will only need adjustment at infrequent
intervals. Before adjusting the BAL control however,
ensure that the input coupling switch
is
set
to
GND.
No adjustment should be made until a minimum
of
15
min. warm-up time has lapsed after switch-on, or
immediately after any large change
of
ambient
temperature.
3.4 DISPLAY MODES
The MODE switch determines the form
of
the display.
I.
For single trace display
of
one Y input against the
timebase this switch should be set
to
CHI or CH2 and
the input signal applied to the appropriate input
connector.
2. For dual trace simultaneous display
of
both
Y inputs
against the timebase, this switch should be set
to
DUAL. Two modes
of
beam switching are used and
selected automatically by the sweep rate selected by
the TIME/CM switch. The alternate mode
is
used at
fast sweep rates between 0.2ms/cm and 0.5µs/cm.
At the slower rates from 0.2s/cm
to
0.5ms/cm the
chop mode operates at approx. 500kHz.
3. In the ADD mode, the single trace generated against
the timebase
is
the algebraic sum
of
the CHI and CH2
deflections.
If
the INV CH2
button
is
operated the direction
of
Y
deflection for that channel
is
reversed .
If
used in the
ADD mode, this facility allows the difference
between the CHI and CH2 inputs to be displayed.
The
INV
CH2
button
has no effect on the polarity
of
internal CH2 trigger.
When
examining small differences between large
signals, the effect
of
small errors between the sensit-
ivities
of
the two channels can be overcome by first
connecting one input to
both
channels simultaneously
3
.2
Section 3
and adjusting one
or
other
of
the VARiable SENSitivity
controls
to
obtain a straight line.
4. In the
X-Y
mode, the timebase
is
disabled and the
CH2 input
is
displayed
as
the vertical Y deflection
against the CHI input displayed
as
horizontal, X
deflection. The CHI shift control
is
inoperative and
X position
is
determined only by the X shift control.
The XI 0
MAG
facility
is
also inoperative. X deflection
sensitivity being determined by the CHl controls
only. The X bandwidth
is
limited to
1MHz
and
relative phase shift between X and Y deflections may
exceed 3° above 50kHz.
3.5 TIMEBASE AND X EXPANSION
The sweep speed
of
the internal timebase
is
determined
by
the setting
of
the TIME/CM switch. The VARiable
SWEEP speed control should be set fully clockwise in
the CAL position for calibrated operation
of
the time•
base. This control
is
used
to
slow the sweep rate to
obtain any intermediate sweep rate, between the
calibrated ranges.
For horizontal shift
of
the trace, adjust the X shift
control (horizontal arrows). If close examination
of
any
portion
of
the trace
is
required,
Xl0
expansion can be
introduced by operation
of
the
MAG
button
. This
provides
an
effective trace length
of
l00cm and any
portion
of
this may be selected for viewing on the screen
by operation
of
the X shift control.
3.6 TRIGGER
The timebase may be triggered internally from the CHl
or
CH2 signals by operation
of
the corresponding
TRIGGER
button,
irrespective
of
whether the selected
channel
is
being displayed. Alternatively, the timebase
may be triggered from an external signal applied to the
EXT TRIG sockets when both CHl and CH2 buttons are
operated simultaneously.
Trigger
will
occur at a level on the signal which may be
set by the TRIG LEVEL control with the slope deter-
mined by the ±
button
. When this
button
is
out,
it will
occur
on
a positive-going transition
of
the signal through
the trigger level. When it
is
pushed in, trigger will occur
on
the negative-going transition. Normally triggering can
be obtained from internal deflection signals greater than
2mm
pk/pk
up to about 2MHz but the sensitivity
reduces to about 1cm
pk/pk
at 20MHz. Corresponding
external sensitivity
is
0.25V
pk/pk
to 2MHz and 1.25V
pk/pk
at 20MHz.
With A.C. coupling, the low frequency sensitivity
reduces to Icm
pk/pk
at about 2Hz.
The Ext Trig input impedance
is
approx. I00k/1
0pF
and
c.:are
should be taken not to apply more than 250V d.c.
or pk, a.c. to this socket.
When the BRIGI
IT
LINE
button
is
out or O , the time-
base will free run
in
the absence
of
a correct trigger
sig
nal, to display a bright line or
un
synchronizeddisplay
