Hi, Jeff,
What you have is a normal artifact that is found on any Tek scope
that has a CRT with an internal scan expansion mesh. This mesh is in
the 485, 465, 475, 7000-series, 2200-series and other scopes. The
beam hits this mesh and "scatters". At very slow sweep speeds,
you'll see a halo chasing, catching up and then passing the actual
dot of the beam. Lowering the intensity will reduce the effect. I
find that if the intensity is high enough to make the "shadow"
visible, or especially annoying, it's a good indicator that the
intensity is set too high anyway and should be reduced to extend CRT
life.
Why the mesh? It improves geometry and deflection plate sensitivity
at the sacrifice of beam crispness. You'll notice that any scope
without the mesh (e.g., a 535 or 5110) will have a much sharper
trace. A lot of folks HATE the mesh because it "thickens" the trace.
I don't have a big problem with it. To me, it's still better than
the ¡À1 digit bobble of the trace on a DSO.
Dean
