TECH: Centipede - Small white dots in game play

Archived from groups: rec.games.video.arcade.collecting (More info?)

I just put together a Centipede board and the game plays 100 percent.
Seems like in the black areas there are lines of white moving dots
during game play. Anyone see this before? What could cause this? Bad
cap somewhere? Bad ram? No errors are displayed in self test and the
game runs 100 percent. Anyone have any ideas on what to look for?

John

Archived from groups: rec.games.video.arcade.collecting (More info?)

Hmmmmm. But if I put another working board in the same machine without
turning the brightness/contrast down, it works fine. Think it could be
that this board only needs the contrast/brightness turned down? I did
put a 12.00 mhz crystal in place of the 12.096 crystal. Would that have
mattered?
John

Archived from groups: rec.games.video.arcade.collecting (More info?)

O.K.... So, sprite problem meaning one of the 2101 rams are bad?

John

Archived from groups: rec.games.video.arcade.collecting (More info?)

Interesting.

Maybe we are talking about two different things. Mine almost looks
like retrace lines (that sort of move around) in the black areas. The
lines almost seem to be made up of dots/dashes, and almost resemble
some sort of interference.

But, if I turn the brightness down, these lines go away.

They definitely don't look like the typical retrace lines, though.
And, they definitely don't look like corrupted sprites, etc.

-- Bruce

On 4 Jul 2005 11:42:53 -0700, "Baraka" <grus_jc@yahoo.com> wrote:

>Hmmmmm. But if I put another working board in the same machine without
>turning the brightness/contrast down, it works fine. Think it could be
>that this board only needs the contrast/brightness turned down? I did
>put a 12.00 mhz crystal in place of the 12.096 crystal. Would that have
>mattered?
>John

Archived from groups: rec.games.video.arcade.collecting (More info?)

Hi John,
I've seen this on two or three Centipede boards in the last several years. I
could never figure out what it was. PLEASE post if you figure it out. Also,
tweaking the brightness does make it non-noticeable....but it doesn't really
fix the problem.

Good luck,
Edward
"Baraka" <grus_jc@yahoo.com> wrote in message
news:1120528109.031721.52290@z14g2000cwz.googlegroups.com...
> I'll give this a shot... The game is up at my weekend home. I never
> thought to turn down the brightness..... maybe that would do it. Don't
> know. However, it's weird that another board works fine and this one
> gives me those glimmering dots and the other doesn't. I'll keep ya
> posted. I'll also try burning some 2516 roms or 2716 roms to see if
> maybe the graphic roms are somehow corrupt.
>
> John
>

Archived from groups: rec.games.video.arcade.collecting (More info?)

my centipede also does this, (so does a fellow collectors in my area).
Turn the brightness down a bit. If you have the black level set just right
(as bright a image as possible with a black background) you will see this
interference. Just turn the brightness down a bit.

--
Mickster

Visit my website and see my arcade!!

http://mickster.freeservers.com

"Big Arn" <none> wrote in message
newsinjc15si9s33fpre6746sj2aoa8dafpbr@4ax.com...
> Interesting.
>
> Maybe we are talking about two different things. Mine almost looks
> like retrace lines (that sort of move around) in the black areas. The
> lines almost seem to be made up of dots/dashes, and almost resemble
> some sort of interference.
>
> But, if I turn the brightness down, these lines go away.
>
> They definitely don't look like the typical retrace lines, though.
> And, they definitely don't look like corrupted sprites, etc.
>
> -- Bruce
>
> On 4 Jul 2005 11:42:53 -0700, "Baraka" <grus_jc@yahoo.com> wrote:
>
>>Hmmmmm. But if I put another working board in the same machine without
>>turning the brightness/contrast down, it works fine. Think it could be
>>that this board only needs the contrast/brightness turned down? I did
>>put a 12.00 mhz crystal in place of the 12.096 crystal. Would that have
>>mattered?
>>John
>

Archived from groups: rec.games.video.arcade.collecting (More info?)

Mickey Johnson wrote:
> my centipede also does this, (so does a fellow collectors in my area).
> Turn the brightness down a bit. If you have the black level set just right
> (as bright a image as possible with a black background) you will see this
> interference. Just turn the brightness down a bit.
>
> --
> Mickster
>
> Visit my website and see my arcade!!
>
> http://mickster.freeservers.com
>
> "Big Arn" <none> wrote in message
> newsinjc15si9s33fpre6746sj2aoa8dafpbr@4ax.com...
> > Interesting.
> >
> > Maybe we are talking about two different things. Mine almost looks
> > like retrace lines (that sort of move around) in the black areas. The
> > lines almost seem to be made up of dots/dashes, and almost resemble
> > some sort of interference.
> >
> > But, if I turn the brightness down, these lines go away.
> >
> > They definitely don't look like the typical retrace lines, though.
> > And, they definitely don't look like corrupted sprites, etc.
> >
> > -- Bruce
> >
> > On 4 Jul 2005 11:42:53 -0700, "Baraka" <grus_jc@yahoo.com> wrote:
> >
> >>Hmmmmm. But if I put another working board in the same machine without
> >>turning the brightness/contrast down, it works fine. Think it could be
> >>that this board only needs the contrast/brightness turned down? I did
> >>put a 12.00 mhz crystal in place of the 12.096 crystal. Would that have
> >>mattered?
> >>John
> >

O.K..... I burned 2 new character roms and installed them and still I
get the vertical white lines which look like they are glittering and
stay at the bottom of the screen. It's only in the black area. Game
functions fine without any problems. Any idea on if this is a suspected
ram problem and which location the rams could be not working correctly?
I went into self test and no ram errors are reported. I tried turning
down the brightness and that didn't help. Would the crystal make this
problem? Does it have to be 12.096? I'm using a 12.00mhz crystal.

Thanks....
John

Archived from groups: rec.games.video.arcade.collecting (More info?)

Mark C. Spaeth wrote:
> Baraka <grus_jc@yahoo.com> wrote:
> : O.K..... I burned 2 new character roms and installed them and still I
> : get the vertical white lines which look like they are glittering and
> : stay at the bottom of the screen. It's only in the black area. Game
> : functions fine without any problems. Any idea on if this is a suspected
> : ram problem and which location the rams could be not working correctly?
> : I went into self test and no ram errors are reported. I tried turning
> : down the brightness and that didn't help. Would the crystal make this
> : problem? Does it have to be 12.096? I'm using a 12.00mhz crystal.
>
> 12.096 is fine.
>
> Try replacing the 27ls01
>
> --
> Mark Spaeth mspaeth@mtl.mit.edu
> 50 Vassar St., #38.265 mspaeth@mit.edu
> Cambridge, MA 02139
> (617) 452-2354 http://rgvac.978.org/~mspaeth

Would 12.00mhz be o.k. for the crystal though? Also, where is 27ls01
located on the board? can't find it.

John

Archived from groups: rec.games.video.arcade.collecting (More info?)

Baraka <grus_jc@yahoo.com> wrote:
: Update... O.K. Replaced all 8 2101's and the doted white line glitches
: still appear in the black area at the bottom of the board. I know this
: has to be a ram problem but 2101's definitely weren't the problem. I'm
: zoning in on the 2114 ram's (there are only 2 on the board) at location
: F2 and H2. I'm going to take a safe guess to say that these rams are
: what was causing my problem. I'll report back after I get a chance to
: test this in my machine.

The 2114's have nothing to do with the video.

If the 2101s were glitchy, the ram test would catch it -- and that has
nothing to do with white dots, since the outputs are latched, and go
through a pile of circuitry before coming anywhere near the video outputs.

Once again, the culprit is probably the 82s25/27ls01 at C8, or else
something in that area of the circuit.

I don't know why I'm wasting my time telling you this since you didn't
listen the last time.

--
Mark Spaeth mspaeth@mtl.mit.edu
50 Vassar St., #38.265 mspaeth@mit.edu
Cambridge, MA 02139
(617) 452-2354 http://rgvac.978.org/~mspaeth

Archived from groups: rec.games.video.arcade.collecting (More info?)

<<I'm stumped. Mark, I know you are talking about C8 as being
82s25/27ls01. However, I'm working on a centipede board. C8 is a
DM74S289 IC.

These are all the same. They are some sort of video RAM. I think that
it's used for color in Centipede. Same family as Pac Ls89 that other
games use, but the ls89 is not a good cross. I'll bet that LS289 runs
hot, right? I know it's confusing, since you are used to 74LS chips as
being anything else but RAM, but trust Mark. Replace it before you
waste any more time replacing the wrong RAMs.


Dave

Archived from groups: rec.games.video.arcade.collecting (More info?)

Thanks for the info, ordered a few of these from mark capps. I'll
report back once installed.

John