G
Guest
Guest
Archived from groups: rec.games.video.arcade.collecting (More info?)
Working on a Sega/Gremlin Frogger PCB that seems
to work fine, except for a vertical "graphics trash"
line about 4 or 5 characters from the right that
extends from the bottom of the screen about 1/2 or
2/3 of the way vertically up the screen. It's only
1 or 2 characters wide (think of the text on the
attract screen and that's the width I mean). It
doesn't affect many of the foreground sprites, but
a few of the floating items and the occasional
car is corrupted. The game is still fully playable
and the sounds are fine too. The graphics line is
always at the same place and never changes!
I swapped another working board and found the
problem is tied to the bottom PCB (video half).
I've replaced all of the 74LS20s, two PROMs at
the end (still working on the other 4, but I
pulled them before and even with them gone the
graphics line was still there), replaced the Z80C,
the ribbon cable and the 74LS04 that's socketed at
IC31.
Voltages are reading 4.94Vish at the RAM. I cranked
the voltage-up just to get there, but am getting
5.4 to 5.5 at the edge connector, so some voltages
are being lost on the sound board and ribbon cable.
I piggybacked the RAM as a test and it caused the
game to constantly reset after showing the all "X"s
screen. However, before it would reset it would
start to clear the screen (suggesting the game was
working) until it got to the area of screen where
the graphics trash line is. This happened every
time and once the Xs cleared the graphics trash line
could be seen.
Anyone have any ideas? I wish the RAM was socketed,
so it would be easier to replace to rule it out. I
am thinking this is suggesting a RAM issue, but
wanted to bounce it off folks here first.
Scott C.
Working on a Sega/Gremlin Frogger PCB that seems
to work fine, except for a vertical "graphics trash"
line about 4 or 5 characters from the right that
extends from the bottom of the screen about 1/2 or
2/3 of the way vertically up the screen. It's only
1 or 2 characters wide (think of the text on the
attract screen and that's the width I mean). It
doesn't affect many of the foreground sprites, but
a few of the floating items and the occasional
car is corrupted. The game is still fully playable
and the sounds are fine too. The graphics line is
always at the same place and never changes!
I swapped another working board and found the
problem is tied to the bottom PCB (video half).
I've replaced all of the 74LS20s, two PROMs at
the end (still working on the other 4, but I
pulled them before and even with them gone the
graphics line was still there), replaced the Z80C,
the ribbon cable and the 74LS04 that's socketed at
IC31.
Voltages are reading 4.94Vish at the RAM. I cranked
the voltage-up just to get there, but am getting
5.4 to 5.5 at the edge connector, so some voltages
are being lost on the sound board and ribbon cable.
I piggybacked the RAM as a test and it caused the
game to constantly reset after showing the all "X"s
screen. However, before it would reset it would
start to clear the screen (suggesting the game was
working) until it got to the area of screen where
the graphics trash line is. This happened every
time and once the Xs cleared the graphics trash line
could be seen.
Anyone have any ideas? I wish the RAM was socketed,
so it would be easier to replace to rule it out. I
am thinking this is suggesting a RAM issue, but
wanted to bounce it off folks here first.
Scott C.