Weird colours from VGA output

Discussion about displays and related hardware including MiSTer filters and video settings.
akeley
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Weird colours from VGA output

Unread post by akeley »

So I've finally put my setup together. My MiSTer outputs to CRT TV sets via Direct Video - AG6200 chip dongle - MiST VGA to SCART RGB cable.

Unfortunately the colours are slightly messed up. It's hard to describe, but there is an odd tint (greenish?) on some of them. Pure white is non existent. Some are just downright different - eg red seems orangey, yellow-sickly, blue-cyan, dark green-light green and so on.

Quick example from the Amstrad core (I've tested several cores, also SNES etc, and it happens on all of them).

IMG-20200624-195653.jpg
IMG-20200624-195653.jpg (375.17 KiB) Viewed 7102 times

Here's the real Amstrad

IMG-20200624-195703.jpg
IMG-20200624-195703.jpg (335.03 KiB) Viewed 7102 times

It's really hard to take a photo of CRTs in action so it's not 100% accurate - for example the white on the border of "1942" logo in the first photo is not really white but green-tinted. Still, you can get a rough idea of main differences. I have tested it extensively, with various TV colour settings. My .ini values are okay as well I think (composite sync=1).

Here's the odd thing: this happens on 2 of my Trinitrons (both medium-old, probably end of 90s or early 2000). It does not happen on 2 others though (one really old, one pretty new). So that's rather puzzling. Also, it's fine on a PC CRT VGA monitor. And exactly the same thing happened with my ZX-Uno FPGA board, also from VGA output. Both boards are connected by dedicated cables from experienced builders.

I also have numerous other systems (real and emulated) connected to these TVs via RGB and have never seen these odd colours. So, it's a little mystery, maybe somebody has an idea as to what could be the cause here.
LeftEmpty
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Re: Weird colours from VGA output

Unread post by LeftEmpty »

Probably turn the sync on green switch off on the MiSTer board.
akeley
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Re: Weird colours from VGA output

Unread post by akeley »

But I'm not using the I/O board...
ash2fpga
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Re: Weird colours from VGA output

Unread post by ash2fpga »

Found a few hits when searching for terms: green levels trinitron. For example: https://shmups.system11.org/viewtopic.php?f=6&t=59668

No idea on a specific fix, though.
akeley
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Re: Weird colours from VGA output

Unread post by akeley »

Thank you, I was actually just about to repost this on system11.org myself. That thread you linked to seems to be about the same issue I'm having, and it all makes sense, that some Trintrons don't get along with CSYNC very well. Seems I might need to try some other cables, or mod the ones I have now.
paulbnl
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Re: Weird colours from VGA output

Unread post by paulbnl »

Check this thread: https://www.atari-forum.com/viewtopic.php?f=117&t=35515

A 1k-2k Ohm resistor on the sync line fixes the color issue with some Trinitrons.
akeley
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Re: Weird colours from VGA output

Unread post by akeley »

Nice one, this is very valuable info as well. Even though some of my colours aren't washed out, kinda opposite - they're too Eighties-rave :) It seems that this definitely is the issue with CSync either way, so at least I know what I'm dealing with.

Now just need to find somebody locally to mod the cable for me...got two left hands when it comes to soldering.
retrorepair
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Re: Weird colours from VGA output

Unread post by retrorepair »

FYI, on my Sony Profeel 27", I had to add 75ohm resistors on r, g and b to ground. I added it to csync also.

Before this the brightness was way too high. Looks great now and also looks great on my B&O MX6000.
akeley
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Re: Weird colours from VGA output

Unread post by akeley »

Seems I'm in for a bout of trial & error malarkey. Perhaps its time to lrn2sldr.

I'd maybe not even bother, because it's fine on my new Trinitron (F-line), which has a PVM-level IQ. Unfortunately this one has another super-annoying flaw, the micro jitter/wobble. It's not that visible on games with advanced gfx so I use it for consoles with this kinda software, but for eighties platforms, with simpler gfx, it's unbearable. And my other TV sets, which don't have this problem, have the odd colours instead. Ah, the joys of retro gaming...:D
grizzlybear
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Re: Weird colours from VGA output

Unread post by grizzlybear »

Using the monoprice vga to bnc cables I had horribly washed out colors (too bright, and neither changing tv settings or mister settings helped), however when I inserted an extron in between the mister and the monoprice cables from amazon, it was completely fixed and colors look nearly identical to the originals on my bvm.

hope this helps someone.
Swainy
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Re: Weird colours from VGA output

Unread post by Swainy »

Where did you get the VGA Scart cable from? I use this one and don’t have any issues with my Sony Trinitrons: https://coolnovelties.co.uk/coolnovelti ... 07088.html
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