Re: Bringing up to snuff a Tek 465M


On 16 Feb 2016 13:45:13 -0800, you wrote:

Does anyone know if the "bleed" on the screen is normal for a CRT screen like the one on the
465M? Here's a video of mine as I turn up the intensity:
Yes, it is perfectly normal. It is partly caused by normal scattering, partly (mostly the halo-like disc) by the scan expansion mesh that these CRT's use to increase the horizontal and vertical deviation sensitivity (and possibly reduce the deviation sensitivity to PDA acceleration voltage).
You'll find that intensity is fully satisfactory in almost all cases long before this effect becomes disturbing. Standard good practice is to not increase intensity beyond a level that permits good visibility, for a number of reasons.

It looks normal to me.

I think the ghosting directly surrounding the bright parts of the
trace is secondary emission from the electrons hitting the screen; the
high anode voltage from the PDA (post deflection acceleration) pulls
them back where they strike the phosphor surrounding the current beam
position. All oscilloscopes with PDA display this behavior.

The scan expansion mesh creates a ghost which is *not* aligned with
the beam (except in the very center) and is not normally visible. If
you want to see it, remove the input signal and use a slow sweep so
that you can watch the beam progress across the screen. The ghost
from the scan expansion mesh will follow the beam position catching up
at the center of the screen and then precede the beam to the right.

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