Re: Asteroids Question

On Dec 2, 11:44am, Jess Askey wrote:
> Subject: Re: Asteroids Question
> Chris Loggans wrote:
> >
> > To start a non-policy related thread... I've noticed a strange thing
> > happening on a number of Asteroids PCB's that I have and I thought someone
> > here could shed some light on it. I have about 10 working Asteroids PCB's
> > and I've noticed this occur probably 6-7 of them. Every once and a while,
> > probably once or twice a round, when you shoot an asteroid, it doesn't
> > explode but collapses into a faint, but noticeable solid line. It is
> > usually a vertical line about 2-3" long. While this is occurring,
> > everything else on the screen is perfectly fine? I have tried this on two
> > different machines/monitors and get the same results so it does appear to
be
> > PCB related. Has anyone else ever seen this or know why it is occurring?
>
> Weird one.
>
> Since it collapses into a vertical line, it is obviously a problem in the X
axis
> circuitry. But.. the strange thing is that it doesn't effect the whole
screen, only
> single objects. Since the DAC and everything past it (hereafter refered to as
DAC+)
> basically just follows the vector counters, the Im guessing that the DAC+ is
all okay.
> Esspecially since the 'invisible' position vectors arene't collapsing as well
(which would
> make the whole screen go into vertical line mode).
> So when it draws an Asteroid, the beam (turned off at this point), Moves to
the center
> of the asteroids position. All is okay here. Now the asteroid itself starts
to get drawn
> using the 'draw' instructions in the state machine which starts the vector
position
> counters going and the vector moving to draw a line of the correct slope and
length. If
> the X counter is not incrementing or decrementing, this exact problem would
happen.
> Now Im not too familiar with the Asteroids vector gen, I know things are
done
> differently with the counters on it as compared to games after Tempest? But
Im not sure
> how exactly.
> Anyone know more?

I think you are on to it, Jess. I had a very similar problem with an Asteroids
boardset where all Asteroids were flat lines, and it was due to the clock input
to the counters being bad. I definitely think the problem lies in the
clock/counters area of the circuitry.

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Received on Thu Dec 2 12:49:39 1999