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BG808s magnetics problem? Astig acting odd

 
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perisoft



Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY

Posted: Sun Sep 21, 2008 5:32 pm    Post subject: BG808s magnetics problem? Astig acting odd

So, I'm trying to do a new setup on my BG808s magnetics, which never really got set up right after I swapped the tubes. I'd had the green focusing ok-ish, but everything moved around through the focus range, which was Very Bad.

Anyway, I'd had a really hard time setting up the green last time, but the red and blue were pretty good. I figured I just wasn't doing it right before, but when I went to redo the setup, I found something really off. The 808s has two rings, each with a knob on them.

With the red and blue, both rings and both knobs affect astig, obviously, but on the green the second ring doesn't do anything at all, no matter how I adjust it. This doesn't seem right! Neutral

The only thing I didn't try was rotating the second ring all the way around, 180 degrees from the first one - but it doesn't seem like that should change things.

As it is, I can't get the poor thing to resolve more than 1440x960, and that only barely (ie, 1-on-1-off vertical and horizontal lines are barely discernible. And interlaced vs. progressive makes no difference at all, in any resolution). Given that a Dwin is supposed to be able to resolve 1080i, I think something is seriously off here!

Any advice? Thanks!

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zGman



Joined: 22 May 2006
Posts: 599


Posted: Sun Sep 21, 2008 5:47 pm    Post subject:

Hi David,

How's the new family??

On the BG808S, you have a support for the neckboard, which has a plastic clamp,
which can be turned so that the cpc magnets can slide further foward on the tube neck.
This will make them a little more effective.

Also, for a basic adjustment, set individual color zone focus each to about 55, and
use the little black focus coil clamp handle to loosen the focus coils (also a ring on the frt.)
and slide / twist a bit, looking for the best overall focus. This will help you later.

When you have a cpc magnet centered, it is possible to rotate the knob around the tube long axis.
When setting astig, use an external dot pattern at a low res, say 600x800, and when in the astg
menu you can use the "sharp" control to defocus the dots. otherwise you can set cpc in
the center focus menu with the dot external pattern. That way you are already there to check
for grid movement during focus ramp...

Hope that helps & good luck,
Galen
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Gerbrand



Joined: 13 May 2008
Posts: 199


Posted: Mon Sep 22, 2008 4:24 pm    Post subject:

zGman wrote:

That way you are already there to check
for grid movement during focus ramp...


I found out experimentally, that grid movements during focus adjustments were due to a misalignment between the focus-assembly and the deflection yokes. Does that make sense?

Gerbrand
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Nashou66



Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY

Posted: Mon Sep 22, 2008 4:54 pm    Post subject:

Gerbrand wrote:
zGman wrote:

That way you are already there to check
for grid movement during focus ramp...


I found out experimentally, that grid movements during focus adjustments were due to a misalignment between the focus-assembly and the deflection yokes. Does that make sense?

Gerbrand


The proper astig set up will stop grid movement in focus ramping, i dont think the deflection yoke and focus coil set up has as much to do with it but possibly maybe 5% or so.

Athanasios

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