Yeah, your chroma section needs a lot of work. The vertical banding is due
to either chroma or clock signal (essentially the same thing) being added
to the luma thus making light and dark vertical bands. Try to physically
isolate the signals as much as possible. And make sure you have *very*
good powersupply filtering for your luma power source and every signal that
goes into luma. (eg. /SYNC, /BLANK, LUM[2:0], et al.)
In addition to the banding, you're getting digital ghosts. They are most
easily seen as the blueish patches in the black areas, though they are
visible everywhere on the screen. Power supply filters will help here as
well.
Unless you are buffering the TIA outputs, it's going to be very difficult
to get rid of either of these effects. Because the TIA generates the luma
signals, but it also causes a lot of the digital noise that you're seeing.
You need to be able to separate the analog and digital supplies...off chip
of course.
The red and green bleeding could be because your brightness is too high.
But it's more likely that the color saturation is too high. If you have
connected the blank signal into your chroma, don't. See if that helps.
Otherwise, making chroma perform well is going to suck. A lot.
It could also be that the monitor is out of alignment, but it's a long shot.
Check that with another video source, say a VCR or DVD player.
Another thing that I see affecting your chroma is phase shift relative to
the luma signal. You need to do two things to improve this. with color set
to 0, measure the delay from the luma signals, say LUM1 (I think that's pin 5)
to the chroma signal, COL which is pin 9. Then make sure that the signal
path delay at the end of your video cable, from luma to chroma compensates
for the delay you measured at the chip.
Good luck!
-Chris
On Mon, 8 Mar 2004, Billy Eno wrote:
> Here is a shot that pretty much shows the vertical banding. I am also
> way too bright, so I have to screw with that some too.
>
> Billy
>
> Chris Wilkson wrote:
>
> >Works here too.
> >
> >Billy,
> >
> >Can you get a screenshot? It sounds like chroma bleeding into the
> >luma signal, but I can't be sure without a picture.
> >
> >On Thu, 4 Mar 2004, Andrew Davie wrote:
> >
> >
> >
> >>works fine here
> >>
> >>----- Original Message -----
> >>From: "Adam Thornton" <adam@xxxxxxx>
> >>To: <stella@xxxxxxxxxxx>
> >>Sent: Thursday, March 04, 2004 3:28 PM
> >>Subject: Re: [stella] Composite Video Mod
> >>
> >>
> >>
> >>
> >>>On Wed, 2004-03-03 at 21:51, Billy Eno wrote:
> >>>
> >>>
> >>>
> >>>>http://www.radioactive3.fsnet.co.uk/atari2600.htm
> >>>>
> >>>>
> >>>Can't hit the site.
> >>>
> >>>Adam
> >>>
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>
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