Your monitor is not adjusted properly or capacitor failing in the CRT. Get a alignment lines with colors grid up.

https://www.youtube.com/watch?v=ONUCwXyUu9g

When I had former job repairing CRT and TV I use this similar to this. Important to check out each CRT monitors so they are set to standards.

Cheers,

Ozzuneoj wrote on 2020-05-09, 16:13:

It isn't a screen alignment issue because it shows that line until the first time it scrolls.
[...]
The crazy thing is, I tried the same card in the same computer on two LCDs (a 1280x1024 Dell and a 1024x768 Viewsonic) and they show all text totally normally!

Sorry to say, but it is a screen-alignment problem. For the text mode used by DOS, the CRT has settings that either has the image shifted downward too much or vertically oversized. It's obvious that the line won't disappear until it scrolls - just think about it.

Just run EDIT or QBASIC and you'll see what's going wrong.

derSammler wrote on 2020-05-09, 16:44:

Ozzuneoj wrote on 2020-05-09, 16:13:

It isn't a screen alignment issue because it shows that line until the first time it scrolls.
[...]
The crazy thing is, I tried the same card in the same computer on two LCDs (a 1280x1024 Dell and a 1024x768 Viewsonic) and they show all text totally normally!

Sorry to say, but it is a screen-alignment problem. For the text mode used by DOS, the CRT has settings that either has the image shifted downward too much or vertically oversized. It's obvious that the line won't disappear until it scrolls - just think about it.

Just run EDIT or QBASIC and you'll see what's going wrong.

The CRT works fine with every other video card.

I guess I need pictures to explain this better. It really doesn't look like an alignment issue. Why would it show the bottom line of text perfectly (at the bottom of the screen), and then once I've hit enter the text that replaces that exact line (same exact position on the CRT) is now invisible?

there's nothing wrong with your video card or CRTs, there is simply a certain amount of tolerance in scan-out frequencies between video cards

just so happens that particular video card overscans the vertical a little bit more, no big deal

Oh my... well, thank you for the help guys. I'm a moron. (Big surprise)

I have a nearly identical card (Sierra Scream'n 3D Verite 1000... made by Canopus) so I threw that in and I was getting the same issue. It doesn't do this with other cards, so I had totally ruled out screen scaling as being the issue. I could literally turn the system off, put in another old VGA card, turn it on and it would look identical except the bottom line was visible as it should be. Surely it couldn't have been the monitor. (derp)

Welp... apparently these Canopus cards must use some slightly different video mode because the placement of the image on my CRT actually *was* set lower than the DOS text mode on my other cards. I adjusted the image up a bit and sure enough, there was the C: prompt.

😩 How did I misdiagnose this so badly last year when I was monkeying with this thing? I checked it again recently and determined "YUP, bottom line is still not visible. I must have been super thorough in testing it last time, and my memory is so great that I can't possibly be misremembering all the steps I took... so I'll go to the internet and ask for help now."

I could have sworn that I could see the first line I was typing on before, but I obviously couldn't have.

Anyway, good news is that the monitor and video card are fine. *whew*

My brain, however, could probably use some replacement capacitors or something.

Thanks again Vogons.

No problem! This is the reason why I test several resolutions when calibrating the CRT monitors, My previous job was Samsung authorized along with few brands authorized us to fix theirs in warranty and able to repair out of warranty as well, meant I had special jig tools that allowed me to access monitor's internal settings using a computer. I cross check using many resolutions and Hz to be consistent.

Best one I had for video source was Matrox G400 dual head for this task. The test gear I brought for test generator patterns was not calibrated or to the VESA timing specs.

Dumb monitors (non-digital) that uses knobs does not have the flexibility even it has lot of scan circuits built in to switch in or out has large overlap.

I had dumb monitors CRT do this as well.

Cheers,