TECH: Pac-Man corrupt sprites

Discussion:

(too old to reply)

Rob Carroll

2004-04-06 03:42:42 UTC

Hey guys,
OK, working on a Pac-Man that is giving me trouble. The moving sprites
(Pac, ghosts, Super-Pac in intermission) and the fruit all have horizontal
lines through them.

I have tried replacing the 2125s at 2A-2D, no change. Tried grounding a few
outputs, but can't locate any faults. Cleaned and resocketed all socketed
chips, re-tinned the edge connector, +5 is balls-on... nothing is even
running hot.

Having trouble with my camera, and too tired to f**k with it, but I do have
some pics fo you tomorrow if you need to see them... but, basically it's
horizonal lines through the sprites. Maze and dots are fine. Non-moving
ghosts in attract mode are also fine.

And before somebody tells me to look through Google, done that. Nothing on
my problem. Close, but not quite.

Yes, I looked through Mowerman's Pac-FAQ and the Midway troubleshooting
guides. Not much help.

Anybody got any ideas before I end up shorting the wrong pin (shaky hands)?

Thanks,
Rob

Steve Lewinsky

2004-04-06 12:45:31 UTC

Permalink

Have you tested your ROMs? or the address lines to the ROMs? One may be
stuck.

Post by Rob Carroll
Hey guys,
OK, working on a Pac-Man that is giving me trouble. The moving sprites
(Pac, ghosts, Super-Pac in intermission) and the fruit all have horizontal
lines through them.
I have tried replacing the 2125s at 2A-2D, no change. Tried grounding a few
outputs, but can't locate any faults. Cleaned and resocketed all socketed
chips, re-tinned the edge connector, +5 is balls-on... nothing is even
running hot.
Having trouble with my camera, and too tired to f**k with it, but I do have
some pics fo you tomorrow if you need to see them... but, basically it's
horizonal lines through the sprites. Maze and dots are fine. Non-moving
ghosts in attract mode are also fine.
And before somebody tells me to look through Google, done that. Nothing on
my problem. Close, but not quite.
Yes, I looked through Mowerman's Pac-FAQ and the Midway troubleshooting
guides. Not much help.
Anybody got any ideas before I end up shorting the wrong pin (shaky hands)?
Thanks,
Rob

Jason Souza

2004-04-06 15:24:36 UTC

Permalink

My money would be on ROMs

RobV

2004-04-07 00:42:53 UTC

Permalink

Let us know what you find out. Sprite problems are usually the ROM's however
I have a similar problem with a Crystal Castle and have three different sets
of ROM's for the game and with every set I get the same problem so it must
be something on the board.

Rob

Rob Carroll

2004-04-07 01:23:03 UTC

Permalink

Well, came home and sussed it out. Sure enough, it was the PROM at 5F.

Here's how I found it.

After doing some logic probing, I thought I found a bad address line on the
Z80. Called Mark Spaeth to ask him what he thought. He said what I was
seeing (A15 only pulsing high) is nothing to worry about, that Pacs don't
use the upper address lines much anyway. Then he suggested I swap PROMs 5E
and 5F. Good old Mark.

Tried that, but there was too much garbage on the screen to really tell what
was going on. So, I pulled 5F. Moving sprites were just colored blocks,
but no lines. Replaced 5F and pulled 5E.. sprites had lines again.

Pulled 5F and put 5E in socket 5F... sprites garbled, but no lines.

So, that's that then. I'll be putting a 4-in-1 in this, which replaces 5F
anyway, so I guess I'll just deal with it for now.

Thanks for the suggestions, guys!!

Rob

Post by RobV
Let us know what you find out. Sprite problems are usually the ROM's however
I have a similar problem with a Crystal Castle and have three different sets
of ROM's for the game and with every set I get the same problem so it must
be something on the board.
Rob

few

Post by Rob Carroll
outputs, but can't locate any faults. Cleaned and resocketed all socketed
chips, re-tinned the edge connector, +5 is balls-on... nothing is even
running hot.
Having trouble with my camera, and too tired to f**k with it, but I do

have

Post by Rob Carroll
some pics fo you tomorrow if you need to see them... but, basically it's
horizonal lines through the sprites. Maze and dots are fine.

Non-moving

Post by RobV

Post by Rob Carroll
ghosts in attract mode are also fine.
And before somebody tells me to look through Google, done that. Nothing

Post by Rob Carroll
my problem. Close, but not quite.
Yes, I looked through Mowerman's Pac-FAQ and the Midway troubleshooting
guides. Not much help.
Anybody got any ideas before I end up shorting the wrong pin (shaky

hands)?

Post by Rob Carroll
Thanks,
Rob