Some arcade cores have strange screen issues with VGA/Analog board to CRT

[Gunnder]

So I have everything running great on my LCD TV via HDMI and CRT TV (Sony PVM-14L5) via Analog/VGA out board.

The only exception is that some arcade cores have this weird screen tearing/stretching at the top of the CRT. With HDMI into LCD TV looks fine, just the analog VGA to CRT is like this.

As an example is the Robotron 2048 core. Any idea what this is, why it's happening, and how to correct it? This is running on a Sony PVM-14L5. Thanks!

[paulbnl]

Try the attached core. The Vsync length has been corrected.

[Gunnder]

Thank you so much. I will try it now.

So in general then, there is nothing wrong with my current setup/settings, but it's just a work in progress cores issue(s)?

[ash2fpga]

That pattern at the top looks very similar to SMS running on a Sony BVM A-series.

[Gunnder]

Thank you @paulbnl for the updated Robotron 2048 core. It now works great! No more weird screen issues!

But I have to ask how did you get a hold of this? The newest version on the GitHub page is the one I was running before from 4 months ago (Arcade-Robotron_20200316.rbf) which had the Vsync length issues. Sorry I'm just learning all this as I go, so just trying to understand where some of these files come from since they are not on the official GitHub page.

I could use such updated cores with the Vsync length corrected for a lot of the arcade cores ...at least 50% of them have this same issue.

Also is it possible to rotate the screen in some of the arcade cores that run 90-degrees counter/clockwise? Again seems to work fine via HDMI/LCD, but with analog VGA/CRT they do not rotate.

[paulbnl]

But I have to ask how did you get a hold of this? The newest version on the GitHub page is the one I was running before from 4 months ago (Arcade-Robotron_20200316.rbf) which had the Vsync length issues. Sorry I'm just learning all this as I go, so just trying to understand where some of these files come from since they are not on the official GitHub page.

That's a build of the core from when I was testing the Vsync fix. The fix is already on GitHub but a new version of the core hasn't been released since then.

I could use such updated cores with the Vsync length corrected for a lot of the arcade cores ...at least 50% of them have this same issue.

Can you make a list of the cores that have this issue?

Also is it possible to rotate the screen in some of the arcade cores that run 90-degrees counter/clockwise? Again seems to work fine via HDMI/LCD, but with analog VGA/CRT they do not rotate.

You can only rotate if you enable the vga_scaler with a custom resolution but it will look terrible at 240p.

[retrorepair]

As an aside to this, arcade pcbs usually have very different sync requirements to consumer electronics as arcade monitors don't have to worry about things like "broadcast safe area" and large porches to accommodate composite sync information (since usually, composite sync doesn't exist).

Anyone who has used arcade pcbs with a supergun in the past will have come across this issue, one that sticks out in my mind was Mortal Kombat which didn't sync at all on my Sony TV. Same with Seibu SPI games.

I have not looked at the "fix" on this core in particular, but most of the arcade cores with sync issues are probably related to the above.

This is why I think a image shift function is necessary at least for some cores, mostly arcade (though it would be a nice option for all of them really). I wouldn't hold my breath but it would be better than having lots of unofficial builds floating about with various "fixes".