Fortress Technologies An E1T Timepiece, Руководство пользователя

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7. E1T Deflection Plate x'' and
anode 2.
A x100 probe was used with
DC coupling. In this image the
cyan trace (channel 2) shows
the position of the ground
(0V).
A few observations:
The high pulse at the start of
the cycle (below the T symbol)
reaches nearly 300V or the
+HT supply. This occurs when
the negative pulse to the grid
has cut off the electron flow.
This will mean that when the
tube is turned on again at the
end of the reset pulse the beam will be in position '0' as required.
The voltage of the '0' step is about 228V and the lowest, just after '9', is 94V. Therefore the
voltage per step is (228 - 94)/10 = 13.4V. This just about corresponds to the step voltage of 13.6V
for counting.
Understanding E1T “Faults”
I call these “faults” but they are part of the charm of the E1T. From the Fortress clock point of view
they are not faults of the Fortress clock but faults in the E1T tubes themselves. Before blaming the
Fortress clock you might take some simple steps of swapping the tubes around to see if the fault
moves or not. If the fault doesn't move then you can begin to suspect the clock hardware and not
the tube.
Most E1T tubes do not light up perfectly from positions '0' to ‘9' in identical fashion.
Manufacturing differences mean that the glow or glows have different intensities. Other faults
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are real - the tube doesn't count or has physical defects.
Spurious lines
The most common ‘faults’ seen on an E1T, even perhaps most
E1T tubes, are additional fainter lines: Here's a tube in position
'3' with a fainter '2' lit. The explanation for this is asymmetrical
deflection. Deflection plate x' operates at a fixed voltage but
deflection plate x'' (as shown above using an oscilloscope)
varies. This asymmetrical deflection causes the electron beam
to widen as it moves towards the left (as seen from the electron
gun) which is the higher numbered positions on the E1T.
These tubes were made in the 1950’s after all….
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Page 75 Version 1.0 Copyright Grahame Marsh/Nick Stock 2019