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AuthorTopic: Graphical issues  (Read 509 times)

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Offline looren

Graphical issues
« on: January 19, 2021, 10:12:02 PM »
Hi

I've had my 1200 recapped a few years ago, and after getting it back I was stoked to launch some good old games on it.
Although upon trying several games I noticed graphical problems. First I thought it was the floppy the games were loaded from, but as I had double copies of some of them I could confirm that the exact same issues were found on the copies also. James pond and Pang are two titles I remember having issues.
I can't boot up my 1200 at the moment, as I'm still looking for someone that can repair my old Commodore monitor (high pitch sound), but I did find a thread in another forum where a guy describes and shows the exact same issue as I have on my 1200:
https://www.radios-tv.co.uk/community/vintage-computers/amiga-a500-graphics-problem/

Just looking for some input in preparation.
Is anyone here familiar with the problem or know how this might be solved? Is it the memory that might be the issue as is being discussed in the forum?
 

Offline TribbleSmasher

Re: Graphical issues
« Reply #1 on: January 19, 2021, 10:26:36 PM »
Somehow i am missing the time frame on this. You just tried it or did you just remember when you tried it several years ago?
Quote
I've had my 1200 recapped a few years ago, and after getting it back I was stoked to launch some good old games on it.
Although upon trying several games I noticed graphical problems.
 

Offline looren

Re: Graphical issues
« Reply #2 on: January 20, 2021, 12:07:53 AM »
I noticed this like two years ago, and kind of gave up for the moment given that both the screen was/is giving up and there was this strange problem with the 1200. Thought I'd revisit the problem, if anyone has a clue on what it might be, and/or a solution to it.
 

Offline TribbleSmasher

Re: Graphical issues
« Reply #3 on: January 20, 2021, 12:18:54 AM »
We still need more information. Did you use the RF output while noticing the issues, or Composite or RGB?
Recapping was done with quality electrolytics or ceramics?
If the faults appeared right after recapping, did you get diagnostics for that? Fixes maybe?
Is the power supply reliable? I mean seriously reliable and trustworthy? How old is it?

and so on.
 

Offline looren

Re: Graphical issues
« Reply #4 on: January 20, 2021, 12:47:09 AM »
Guessing its RGB for the 1084s monitor? right?

I'm assuming it was done properly. The guy who recapped makes both hardware and software stuff for Amiga and seem pretty active with everything. What type is used, I don't know. He said it has nothing to do with the recapping tho.

I never turned on the 1200 before having it recapped, as its been in storage for a long time. I didn't want to risk it in case any caps were leaking, so I really can't say if the problem existed before it being recapped.

I used my original 500 power supply, and it has also been recapped.

I take it from your answer, this issue isn't common.
All I know is that its always the same graphics that gets screwed up. For example: https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/249/6587-3.jpg
It will always be the background that is screwed, and the sprites will be as expected.

Or like here: https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/249/6588-4.jpg
Background will be screwed and text will always be fine.
 

Offline TribbleSmasher

Re: Graphical issues
« Reply #5 on: January 20, 2021, 01:19:41 AM »
If it looks the same on your A1200 it might be a memory issue as you said, or an address issue (chip pins corroded perhaps) or some other hardware issue.
Normally you would need to show the board to somebody with knowledge of electronics, preferably Amiga, in your area to rule out hardware defects.

Of course you can still try to boot your Amiga without the monitor, just find an adaptor cable to connect it to a tv.
 

Offline Pat the Cat

Re: Graphical issues
« Reply #6 on: January 20, 2021, 03:23:38 AM »
it could be one of several things;-

1) Bad memory chip, U18-U19. (Upper MB, because games loading OK, computer starts up OK). Likely cause static damage

2) Bad connection beteen the memory chips and the custom chips (tiny break or short, maybe from the recap).

3) Bad custom chip, Alice but most likely Lisa. The memory and pathways are fine, but the chip isn't reading it properly.

If you do a memory check of the machine, I guess that could rule out option 1 at least, if it passes. It will only test the paths between the processor and the memory chips though, could still be OK custom chips but maybe a board fault somewhere between the memory chips and the custom chips.

It definitely looks like it's digital, rather than  when it gets turned into an analog signal.

https://aminet.net/package/util/moni/CheckMem

https://github.com/keirf/Amiga-Stuff#amiga-stuff-native--cross-dev-code--tools-for-amigas

Duff memory chip would be easier to find replacement. Than a duff Alice or Lisa.
« Last Edit: January 20, 2021, 06:18:16 PM by Pat the Cat »
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