VOGONS


First post, by cprieto

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Hello everyone...

I recently got a new LCD for my retro stuff (19" SyncMaster 940b) and I had been trying a few PCI and AGP video cards and noticed something weird:

IMG_20210120_155205.jpg
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Weird ghost line
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As you may see, there are weird ghost lines and black smudges in the image, the same happens in other parts of the Window, for example, the file menu:

It is hard to see with a picture taken from a phone camera, but the "File" and "Help" menu has weird black smudges, like when you use the smudge tool in a program like Paint.net or something like that. You can see the same in the "Color" menu item.

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Weird menu smudges
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This happens in resolutions beyond 800x600 in both 256 colors or more. I already tried with 5 different cards (MGA 200G, TGUI9660-1, S3 Virge/GX, S3 Trio64V and ATI Rage IIc) and I get the same problem. Just to make sure I tried in another old LCD monitor, a Belinea 1705G and I get the same result.

I tried using auto adjust and nah, the problem is still there in those resolutions and get worse with higher resolutions (for example 1280x1024 in the MGA 200G).

All of this using the "official" Win3x drivers and all of that.

Any idea what is happening?

Thanks!

Reply 1 of 6, by dionb

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Looks like a bad cable, or bad analog circuitry in card and/or monitor.

Given you've tried five different cards, including the known excellent Matrox G200, I doubt it's primarily in the cards. So I suspect a bad cable, or otherwise two bad monitors. What happens if you hook it up to a recentt, known-good monitor (your daily driver)?

Reply 2 of 6, by megatron-uk

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It looks like you've got two different things going on:

1. It seems that the resolution being output isn't an integer multiple of the native res of the screen. That's usually the cause of the vertical 'jailbars' on LCD screens. That Syncmaster has a native res of 1280x1024, unless you output that res, or an integer multiple/divisor of it, you will get banding like you see. It's something that just didn't happen on CRT technology... but being a middle-aged guy, I can put up with that compared to living through the 80's and 90's and having phosphor tubes burning in to my eyes all day! 😁

2. The second, the smudged, blurred, image-ghosting is, I would agree, caused by poor shielding on the VGA cable (try a shorter one with shielded cables and/or ferrite beads around each end to reduce high frequency noise). If it occurs on multiple cards then it's unlike to be the source device/card/GPU. Display cable (longer cables pick up more noise), or power supply in the monitor can all be culprits.

Given you've said it gets worse above 800x600, it sounds like the higher the frequencies on the cable, the more interference it is picking up.

Try to reduce the length of the cable. Try a shielded cable. Keep it away from any mains power cables on its way to the monitor. That's about all you can do, or replace the monitor with something that isn't as suscptible to the interference - easier said than done of course!

Reply 3 of 6, by cprieto

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thanks @dionb and @megatron-uk, I think it could be the cable, it was something I got extremely cheap months ago, I will be ordering a new shorter and more nicer cable to try again.

About the resolution, I actually tried with the native resolution for that screen with the MGA (1280x1024) and the same problem occurs so I will say it is the cable 😀

Once I try again with a new cable I will report if that fixed the problem.