Morris Odell <morriso@...>
Well, GenRad was not exactly averse to non-50 Ohm lines and connectors, soWithout going into the details of its design, I suspect the 125 ohm
environment was used in the 519 because of its unique CRT. The distributed
deflection system is a single ended arrangement with 125 ohm GR connections
for the input and the termination. A similar but much more advances system
is used in the 7000 series high speed scopes.
The 519 CRT contains several in-line vertical deflection plates connected to
a pre-aligned delay line. Y shift is acheived by controlling the voltage to
the other plate which is at AC ground potential. Inside the scope there's no
vertical amp, only a delay line consisting of a coil of rigid coaxial line
between the input connector and the CRT.
The 125 ohm GR connectors look like the 50 ohm ones from the outside, but
the centre connector is different - it's a sort of "fork" arrangement with a
smaller diameter to match the higher characteristic impedance. It looks more
fragile than the 50 ohm GR system.