Apple 8.24 GC artifacts

[ObeyDaleks]

Hey all,

One of my 8.24 GCs has this odd behavior. In black and white mode, it has these faint blue vertical lines. They disappear when I use higher color modes. Any idea how to troubleshoot this? I don't see any physical damage and most of the components look fine. I tried reflowing the vram ICs but that didn't help.

 

[joevt]

They disappear when I use higher color modes.

Including 4 color mode, 16 color mode, and 256 color mode?

In B&W color mode, the lines appear to occur every 8 pixels but do not appear on solid black or solid white backgrounds? That is strange.
Some of the text has blue fringing? The problem seems to occur where transitions from black to white or vice versa occur?

Does the problem occur with different resolutions?
Does the problem occur with different desktop patterns?
Does the problem occur with different desktop colors?

 

[nathall]

I also find it interesting that setting the card to ”millions” of greys actually displays things in color, not greyscale.

 

[ObeyDaleks]

So it’s a bit inconsistent. I was able to reproduce a similar issue in 256 color mode, only with a very specific desktop pattern. So it's not just black and white. But other than that specific case, the artifacts are gone in 4/16/256/millions of colors. Solid black or solid white desktop pattern doesn't have this issue in any color-depth. But in black and white mode, even the windows and text have blue splotches next to it. I haven't tested with a different monitor yet to try other resolutions. I might have to dig one up.

 

[ObeyDaleks]

I also find it interesting that setting the card to ”millions” of greys actually displays things in color, not greyscale.

I believe 24-bit is always in color, i.e. there isn't a setting for millions of grays. So the control panel just automatically assumes it will be color.

 

[Arbee]

Correct, millions is always in color. Probably because 24-bit pure grayscale is really just 256 shades.

 

[captaineos]

I have the same fault, but assumed it was my logic board partly to blame I have recapped the video card but yes identical symptoms and no idea why