Re: Asteroids and 'wiggly' diagonal lines

If you have spaces where nothing ever gets displayed I would be looking
at the counters.

If the objects, however, have SLIGHT forward or backward "wraps" at
certain areas you may have a non-monotonic DAC. If the only place is in
the center of the screen (left right centerline or top bottom
centerline) it could be the DAC or crossover distortion in the monitor.
In that case using a scope as an XY monitor will show you for sure. A
scope will NOT have crossover distortion so you can readily see if the
DAC (or an op-amp after the DAC) is causing the problem.

Aaron Howald wrote:
>
> ----- Original Message -----
> From: "Jess Askey" <jess@askey.org>
> To: <vectorlist@synthcom.com>
> Sent: Sunday, January 13, 2002 2:54 PM
> Subject: Re: VECTOR: Asteroids and 'wiggly' diagonal lines
>
> > I think someone else briefly mentioned this but if you have an mysterious
> > invisible line of distortion then it usually means a bad bit output on one of
> > the vector counters. I think they are 74LS191's? I had this problem once
> > before, if the line is vertical then look in X counters and horizontal would be
> > Y counters. Since the bit is faulty you can usually track it down by simply
> > putting the game onto the crosshatch screen and then making sure that all
> > outputs of the vector counters are pulsing with a logic probe. If one is stuck
> > high or low, then you can make a good guess that that output is faulty (unless
> > what it connects to is holding it steady).
>
> I once saw an asteroids machine with huge gaps in the characters.
> The gaps were horizontal, evenly spaced across the screen, and "warped" graphics
> as they passed over these bad areas. No lines wanted to be in these
> areas, they would be "jumped over" I suspect this was the same
> problem mentioned above, but with many bits or a high bit being stuck.
>
> Aaron H.
>
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Received on Sun Jan 13 16:52:04 2002