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4 CIRCUIT DESCRIPTION
4-5
4.3 CRT CIRCUIT
4.3.1
Z-axis amplifier
The Z amplifier provides intensity control of the CRT by driving the Wehnelt-cylinder g1
(pin 3), and focus control by means of the focus electrode g3 (pin 4). The voltage to the
Wehnelt can be influenced by several signals.
Inputs to the Z-axis amplifier are :
-
ADC control signal to R3026.
This voltage
is 0 V in position "X DEFL"
of the TIME/DIV
switch
and
+5 V in
the other
positions.
-
"INTENS", intensity control to R3029.
This is a DC
signal, 0 to
+12
V, from the "INTENSITY"
control
RV3033.
The
signal
is intended
to control
the intensity of the beam.
-
"MTB UNBLANK", unblanking signal MTB, to D3027.
During the MTB,
this logic signal is HIGH,
and the MTB
can
be displayed.
-
"CHOP BLANK", blanking signal to D3029 and D3031.
This logic signal is HIGH
when
the trace must
be displayed,
and
LOW
during
switching
from
channel
A to channel
B.
-
"Z-AXIS INPUT", to R3001.
This
input consists
of external
signals,
if any, to the BNC
connector
at the
rear-side
of the instrument.
A positive signal
blanks the display;
a signal of
about
3 V is sufficient to blank a display of normal
intensity. All signals
mentioned
above
influence
the voltage at gi and thus the trace
intensity.
Z-pulse is available. This is a positive pulse with an amplitude between 0 and 80 V,
Focus control.
4.3 CRT CIRCUIT
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