Re: G08's and inductive kick

Zonn wrote:
>
> At 04:26 PM 8/29/97 -0700, you wrote:
> >I'll bet removing those resistors and replacing the
> >voltage with regulated voltages could possibly give a nice solid display
> >without having to have, high power, low voltage, regulation.
> >
> >yup.. that's what they did in the ampliphone.
> >
> >We also just figured out what the two multipliers do in the WG vector
> >generator design; they multiply the square of the opposite channel's
> >deflection value, scaled down by a voltage divider to the channel's
> >value prior to it being scaled by the pot/VDR linearity circuit.
>
> I posted somewhere what those things were doing, if I wasn't so lazy I'd
> have written a FAQ or something.
>
> >From reading a lot of different sources I found that in some yoke/CRT shape
> combinations (especially the older tubes/yokes) there is an affect where the
> farther from the center of your CRT the beam is, the more affect the yoke
> has on moving it. I never really was able to find out why, maybe something
> to do with the inverse square law and the distance from the gun and the high
> voltage <plate> attracting the electrons. The farther the distance the less
> attractive force, leading to more "blooming".

Blooming is usually caused by low high voltage. Lower the voltage, and
the electrons are
less attracted to the plate. The picture will look expanded.

  Whatever the reason, since
> the diagonal corners are farther from the gun than the center of the screen,
> as the beam moves from the top left corner down towards the lower left
> corner it has reaches a point in the center of the screen where the beam
> travels the least distance

It is almost the same distance from the electron gun to the mask. The
mask and front of the tube is curved to allow for this. It uses less
voltage to repel the electron (with the yoke) in the center of the
screen. The yoke has to get more signal to make the curve
where the neck meets the rest of the tube or deflect the electron from
the HV plate.

and the yoke has less affect, so the beam is not
> deflected as far. Then as it continues its travel when it finally makes it
> to the lower left hand corner it is now farthest away and the yoke has the
> most affect on the beam you end up with the:
>
> .
> .
> .
> .
> .
> .
> .
> .
>
> affect. Since the affect of the X axis is dependent upon the position of
> the Y axis the correction circuit for X is based on Y. I guess since the
> top and bottom of the screen are closer to the guns there is less of this
> sort of effect. I noticed on Tempest they have the pincussioning correction
> for the X and Y axis and have disabled the Y axis correction by not
> populating some resistors.
>
> The linearity corrects the same problem. Blooming at the edges. Since the
> beam has farther to travel towards the edges, the yoke has a greater affect
> and things would get bigger towards the edges if not corrected for.
>
> I don't know why B&W monitors and the newer Color tubes are less affected by
> pincussioning, but are still affected by blooming, except that I've read it
> has to do with the design of the tube/yoke combination.

Newer tubes are shorter on the back of the tube.Less distance for the
electron to travel and B&W tubes do not have three guns to deal with.
Trying to get the triad or three colors to go through the mask is more
difficult than a single beam.

 They've obviously
> extended the distance between the guns and the front of the screen in
> amplifone tubes, the would decrease the distance ratio between the edges of
> the tube and center, maybe that helps. I've noticed all tubes in the newer
> raster displays (there are no *new* X/Y monitors :^( ) have the bulbous
> length of the amplifone tube, this must help them to deal with pincussioning.
>
> -Zonn
Received on Mon Sep 1 07:49:11 1997