Amiga 1200 Graphic Problems -=Please Help=-

I've had several Amiga 1200 computers over the years. The first one, I purchased at Software hut on the web during the late 90's or so. It was brand new and came in a big colorful box with a fairly large software and AGA game bundle. It was only $199 and I was really happy with it.

A couple of years later, I don't remember why, but I sold it. I guess I needed the cash but I always regretted it. Anyway, about 5 or 6 years ago I bought another one. The one I currently own seems to be an original model made by commodore. It even has a small commodore plastic logo on the the keyboard top left corner. My previous A1200 had an Amiga logo with a colorful check mark. Therefore I am assuming this is an original model.

My current 1200 has a VGA port modded into the back, a squirrel SCSI adapter that I use for a CD ROM, and a 69040 (it may be a 68030) accelerator with 32 megs memory. I was happy to get it, it was everything I wanted in an Amiga with the exception of a mini tower case.

I'm having a problem with some games. Some games play horribly with graphic glitches. Many games work great. I use a kick start disk and play with the boot configuration and get many older games to work fine. I also don't have any problems with games like roadkill, pinball illusions, Project X, Super Stardust, but some games just play horribly because of graphic glitches. Some of the game plagued with the graphic glitches are Disposable Hero (such a great game too), Banshee, and super skid-marks. There are more, but off the top of my head, those are the ones I have always loved the most. Banshee has big blotches on the screen where the graphics are messed up.

Could this be a problem with my motherboard? Is there anyway to tell. Can I fix it. At first, I just thought it was flicker from the VGA port so I hooked up up an RGB and a composite monitor and it did the same exact thing. It doesn't matter if the system has been running a while or If I just turned it on, so it's not a heat issue. I thought maybe the 68040 accelerator was the problem, so I took it out, it did the same thing.

As far as the VGA monitor goes, I can run workbench and other apps in hirez without any problems. Also, I seem to have pretty good luck running demos as well.

Other Info : I'm running OS 3.5 on the machine, but I use various degraders and kickstart disks to make older games work. The games that have glitches, I have tried everything along with all the different versions and different boot combinations with no luck. Even when I use the CD32 option with my CD-rom and run the CD-32 version, I still get the glitches. With Disposable hero and banshee. In Disposable Hero, the ship disappears during the game and it doesn't run well at all.

It makes me mad bad that I can play these games under uae on my PC better than I can on the actual hardware.











Any suggestions would be appreciated.




Thanks,
Jeffrey Gibson

[Amiga1992]

Remove the scandoubler (the thing that gives you a VGA output) and try again.

[Hewitson]

Try running these games in WHDLoad if the above suggestion doesn't work. Actually, run them in WHDLoad even if it does work.

1I have tried the whdload version of some of the affected games. It makes no difference. I've pretty much tried every version of banshee and disposable hero that sexists.

But I have run the Amiga using the composite output, wouldn't that bypass the scan doubler? If its a scan doubler issue, how come I one get glitches on some games. Also, the types of glitches I get on the games is usually different.

[emufan]

maybe a ram issue? here is a good working ram-tester. ( for chip and fast ram ).
( /TheZone/files/M1230XA-101 [MBRtest memory test software for Akira].zip )

[Amiga1992]

Originally Posted by retrocomputer22

But I have run the Amiga using the composite output, wouldn't that bypass the scan doubler? .

It doesn't matter. The scandoubler could have damaged the chip legs. It happened to me.
You cannot diagnose the Amiga properly while you have stuff on it. As long as you have it connected I'll suspect it. If it does it without it, then we're looking at another problem and your Amiga is faulty for sure.

RAM could be a problem, but besides graphic corruption it could also yield lockups.
After you removed the scandoubler (be careful when doing so) do as emufan says and run MBRTest.
It does look a bit odd to me as if it was failed rendering. When you have RAM problems, more random garbage is rendered instead .

OK, I took the amiga apart so I could get up close to the scan doubler but now that I have the hood open, I'm not sure what to do. I took pictures but the reply doesn't let me post them here. I shared them on my google drive so you guys could see and advise me. The 1st picture shows the VGA port in the back. The next pictures shows what the VGA connector connects too. It's like a daughter board sitting on top of some other ships. It doesn't look like it comes off easily. I have 2 more pictures showing 2 more places where the VGA also connects too. There's also a couple of more pictures so you can see which version of the mother board I have along with the revision number. The pictures are at

https://drive.google.com/#folders/0B...nFqVWMzd3p5UFU

I shared them and you should be able to access them. If not, let me know.

Thanks in advance.

Jeffrey

[ajk]

You can post photos in the replies by going through the "Go Advanced" button at the bottom.

That link only works if you log into Google, first it took me to the front page of Google Drive.

The scandoubler appears to be a Micronik Scandy, I also used to have one.

can the Micronik Scandy cause graphic problems with some? Is it soldered on? I can't really tell. Here are the pictures again.

Here is the back where the vga port is installed.


Here is where the main part is connected. It looks like a daughter-board and I can't tell if it's soldered or not. If it is, it's not worth trying to remove for testing and I'll just have to suffer as far as the affected games go.


another part runs from the daughterboard to here.


and the last part from the daughterboard to here.

[Havie]

http://joes-tech-blog.blogspot.co.uk...ker-fixer.html

Above link may be of use?

[Amiga1992]

Yes, that's the scandoubler. You just have to pull it. It's pigggybacked to two chips. Don't be afraid, it'll pull easily.

Remember how it went to put it back in in case it isn't the problem, but you already took pics so that should help you out.