Taito Space Invaders Graphics giltch??

DarrenA

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What would cause this issue?

Missing about a 2 1/2" chunck in the center of the screen ?
OK, cant post a pic. says upload failed.....
 
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Is the right side of the screen, actually the left side of the screen, and vice versa? Or is the screen in the right place, it just has a black stripe down the middle?


If it's backwards, it's probably a sync or vertical hold issue. You may be able to adjust it out with your vertical hold adjustment.
 
Capacitors.

I had a G07 13" in a MrDo's WildRide cocktail and it had about a 2" black "blob" just right and up from the center of the screen. Absolutely dead black and it floated a tiny bit.

A new cap kit fixed the problem.

EDIT: Okay, now that you got a picture posted -- your problem is memory or address related... not a monitor issue.
 
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Actually you know what it is... I think you have a half screen mirror going on here.

Take a look at this site for pac boards:
http://www.arcadegameover.com/pactrouble.html

Look at some of these "similar" issues and see if that leads you to a similar solution on the SI.
Image100.jpg
Image101.jpg
Image3.jpg
 
Looks to me like maybe an issue related to the video hardware's RAM addressing... like an address line is stuck somewhere. Look to the left of the RAMs on the schematics; D5, E5, E6, E7, data selectors (F4, F5, F6, F7), and the associated logic too.
 
Thanks for the replies. It is def, not mirror. when I stick the roms in everything works, "but that part in the center". I will look at those DarrenF pointed out. I have a ton of those 74 series chips, so I think I will just start by replacing the 3 that had me stumped that I thought were acting funny.
I will keep you all informed.
 
OK, So I changed on the CPU board
Component location

3,4,5,6,7,8,11,12,18,19,26,27,28,29,34,35,42,43,44 and all of the RAM,

ROM Board
4,5,6,7,8,29,30

Still no change.
Now mind you, I had to replace a few of these because they were shot,
RAM, the 4 161's on the ROM board and the 74241"s on the CPU board as these were 100% shot. the board would not even boot untill I had replaced most of them. And I always replace RAM no matter.

Could there be a add Line from the CPU that is out??
I pretty much changed everything else that is in those lines...... So thats why I ask.
 
OK, So I changed on the CPU board
Component location

3,4,5,6,7,8,11,12,18,19,26,27,28,29,34,35,42,43,44 and all of the RAM,

ROM Board
4,5,6,7,8,29,30

Still no change.
Now mind you, I had to replace a few of these because they were shot,
RAM, the 4 161's on the ROM board and the 74241"s on the CPU board as these were 100% shot. the board would not even boot untill I had replaced most of them. And I always replace RAM no matter.

Could there be a add Line from the CPU that is out??
I pretty much changed everything else that is in those lines...... So thats why I ask.

Oh, I didn't notice you're talking Taito and I was quoting IC locations and the Midway SI schematics. I've never taken a look at the Taito documentation, but I assume it has to be quite similar functionally.

You said with the game roms, it boots and plays with a "dead" strip of screen. This would likely not happen with a bad CPU address line; it would instead crash/reboot/watchdog due to the inability of it to properly retrieve commands from ROM. Because it appears to be an "output only," issue, I'm thinking video hardware. The video hardware shares the RAM with the CPU bus, but addresses it sequentially to read out the video display. That's why I'm thinking something in THAT set of addressing (or the multiplexers that allow sharing of the address lines) is the place to stick your logic probe or scope.
 
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