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82
T Y P E
6 0 3
E L E C T R O N I C
M U L T I P L I E R
,
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/
'
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Stor1 of
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negative
pulse
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voltape increose i f
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:either l u b e conducts
Figure 80. Oscillograrn o f Actual Grid Voltages During Triggering
the grids can be determined as shown graphically
in Figure 79.
While these curves could be accurately calcu-
lated, they were actually obtained by plotting an
ex curve between the known limits of grid poten-
tial.
This
gives
a
theoretical capacitor discharg-
ing or charging curve. Because of the much great-
er swing in potential on the grid of
TI,
caused by
the relatively low potential existing on the capa-
citor C c between the grid of
TI and the anode of
T2,
i t
is obvious that the rate of potential rise will
be much greater than the rate of rise in the poten-
tial on the grid of
TZ.
I t is evident that the grid
of
TI,
which has been non-conducting, is the first
to rise above the conducting point of
-8
volts.
These tubes cut off at
-8
volts, therefore conduc-
tion
will
start as soon as a grid goes above .this
potential.
Hence
TI
starts conducting and blocks
' T Z
from conducting as previously explained, and
the trigger is reversed. The action of the capacitors
Cc produce the desired trigger action, and the trig-
ger will now reverse itsclf every time the g i d s are
given a negative pulse of 20 volts or more.
I n Figure 78 it was assumed that the capacitors
Cc were much larger than the grid capacitors
Ci.
As evidence that this assumption does not alter the
general shape of the curves of grid potential rise,
Figure 80 shows a sketch of the grid potential rise
in an actual trigger circuit. This sketch is adapted
from an actual oscilloscope pattern and shows
exactly what happens t o the grids of TI and TZ.
Originally T Z was conducting and TI was held
non-conducting by the -30 volt potential on its
grid as shown previously. A t time t (Figure 8 0 )
a 20 volt negative pulse is applied to both g i d s
through the input capacitors Ci. Owing t o the fact.
that the square wave input is not perfectly square,
the neggtive pulse as it appears a t the grids is not
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