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Old 06 October 2018, 18:09   #1
Born2Rune
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A1200 graphical glitches.

Hi Guys,

I recently purchased a A1200 and seem to be having issues in a lot of games regarding graphical glitches mostly when scrolling. I have slightly modified the Amiga with an internal SD reader and also a Gotek (but with no extra RAM, WHDLOAD is pretty useless, hence the Gotek). I have used multiple ADF's of the same games but getting the same result.

I have checked the motherboard and it seems that I do not have any leaking caps (but I still have an untrained eye so I may have missed something). Looking around the internet for an idea on where to begin has been fruitless. I did find a post on here with a kind of similar issue and folks was pointing to a PSU going bad.

So my question is, would a bad PSU be causing my issue?. I would like to have a rough idea before attempting to buy a new one. I do not have the skills for a PSU recap and just seems less hassle to just buy a new one off of eBay or somewhere.

Sorry for the long post, and thanks for the help.
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Old 06 October 2018, 19:16   #2
indigolemon
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Before we start answering your question - can I just check, are you, by any chance, the Dean of a University?

Leaking caps can be really very subtle, showing as some tarnishing on the solder at the base of the cap (it should be reasonably shiny).

Can you get some video of the issues you're facing and put them up somewhere so we can see it?
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Old 07 October 2018, 18:37   #3
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HA!, I might very well be, I'm still working on my leather jacket and bone chopper but bloody students keep getting in the way!. You would think this place is somewhere where you go to learn.

Thanks for the response, here's a youtube video of it happening in Kid Chaos, some games are worse than others. The Settlers is unplayable even when not scrolling and same with Cannon Fodder.

[ Show youtube player ]
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Old 07 October 2018, 18:45   #4
indigolemon
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How is the Amiga connected to the TV?
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Old 08 October 2018, 16:41   #5
Born2Rune
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Its through RGB SCART, so connects on the Amiga monitor port. You gave me an idea to try some RGB cables from my NES to see if it was the SCART cable, and I got the same result. I also tried on a modern monitor via HDMI converter and same result.
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Old 08 October 2018, 17:17   #6
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It looks more like a software issue. Bitplane pointers or scroll values being off at certain horizontal scroll positions. Have you tried booting with original chipset / aga disabled? Are you able to try any of the same games with whdload? (install 'wbrun', boot without startup sequence and start the whdload icons using it to save memory)

Edit: Well, could be a minor hardware issue too I guess causing some odd things if you're absolutely not running or have installed anything that could change the behaviour of the games.

Do all games with hardware scrolling should have issues? generally games that scroll smoothly. Games that are kind of slow probably use just blitter and shouldn't have bugs (like the Chaos Engine)?

Last edited by dodke; 08 October 2018 at 17:28.
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Old 08 October 2018, 18:09   #7
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Quote:
Originally Posted by dodke View Post
It looks more like a software issue. Bitplane pointers or scroll values being off at certain horizontal scroll positions. Have you tried booting with original chipset / aga disabled? Are you able to try any of the same games with whdload? (install 'wbrun', boot without startup sequence and start the whdload icons using it to save memory)

Edit: Well, could be a minor hardware issue too I guess causing some odd things if you're absolutely not running or have installed anything that could change the behaviour of the games.

Do all games with hardware scrolling should have issues? generally games that scroll smoothly. Games that are kind of slow probably use just blitter and shouldn't have bugs (like the Chaos Engine)?

Thanks for the reply, there are some games that run in WHDLOAD such as Agony, so I booted that up and same scrolling effects as running it on the GOTEK emu. I have not tried Chaos Engine yet on the GOTEK as I have to go to work in a moment so don't have time to try.

I was thinking it could be the Blitter as well as Workbench is fine and Shufflepuck Cafe is fine too. Maybe the Amiga is not getting good enough power from the original PSU and causing the corruption?. Or a bad cap near the chip?.
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Old 08 October 2018, 23:31   #8
nexus
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checking for leaks isnt how you determine if caps are good or bad
caps do not have to leak or vent out to be bad
only thing looking for leaks does is too know 100% that a cap is bad and what serious damage it may have caused to other components and PCB
why you also look at dull solder joints as the acid eats at them causing that

Last edited by nexus; 08 October 2018 at 23:36.
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Old 08 October 2018, 23:34   #9
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Yeah, that could be a chipset incompatibility, or a small hardware issue as dodke points out. I don't know Kid Chaos, but I do know that both Settlers and Cannon Fodder load from floppy on an A1200 without any issues. It's a regular enough that it looks like it's glitching as it hits the end of the scroll buffer, so unless there's something funky up with the cracks on those games, it's more than likely a hardware issue. Just to be sure however, you should disable the SD card "hard drive" altogether, either remove it, or use the early startup menu to disable all partitions. Mounted partitions consume a certain amount of RAM even if you boot from floppy, so it's worth ruling out.
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Old 08 October 2018, 23:40   #10
nexus
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try disconnecting the gotek after game is booted see if it happens
see if its a power issue
while testing a PPC PCI in a A4000 build that had a bad 5v PSU the gotek being off gave me enough extra to power it and be stable
not sure how much power those goteks actually use
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Old 09 October 2018, 19:12   #11
Hewitson
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Quote:
Originally Posted by nexus View Post
checking for leaks isnt how you determine if caps are good or bad
caps do not have to leak or vent out to be bad
only thing looking for leaks does is too know 100% that a cap is bad and what serious damage it may have caused to other components and PCB
why you also look at dull solder joints as the acid eats at them causing that
Looking at the solder joints isn't a very effective method either. A cap can be bad, but not have leaked.

There's only one proper way to test a capacitor, and that's with an ESR meter.
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Old 09 October 2018, 19:17   #12
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Sorry for the late response, I work nights and 12hr shifts so been a bit difficult to troubleshoot. But I'm off for 4 days so I can have a good crack at it.

So, what I have done:

I took Daedalus advise and took the SD loader out of the IDE just in case it was causing memory usage and booted into a game via the GOTEK and same issue. The graphics corruption.

Now I just had 2 issues today that is leading me to getting a new PSU first. First off the Amiga started rebooting itself for no reason on the insert floppy screen when I removed the SD loader. The second, and could be just a poor USB stick, but it lost the MBR and I had to reformat the whole stick. I know sometimes USB drives can take a dive when the voltages are wrong etc.

I am leaning to getting a new PSU as a first line of attack before getting a recap service done. I am not experienced enough in soldering to attempt a recap project off myself.
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Old 09 October 2018, 19:34   #13
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Just in case it happens again in the future, you don't have to reformat a drive because you've lost the partition table. No actual data has been lost, simply creating a new partition of the same size would have rescued the drive
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Old 09 October 2018, 19:40   #14
Born2Rune
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Just in case it happens again in the future, you don't have to reformat a drive because you've lost the partition table. No actual data has been lost, simply creating a new partition of the same size would have rescued the drive
Bugger!, I lost hours of game curation on that LOL. No matter, will give me something to do.
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