IBM 5151 display questions

[kingchops]

I managed to get my hands on an IBM 5151 monochrome display. Was the usual ebay purchase and it was untested so I didn't know if it even worked. But gladly when I configured my video card to output in monochrome mode I got it working. Seems to work ok but I'm having some issues getting the ideal video mode. When I fire the pc up (5150), the display mode takes up most of the screen but to the very right on the screen the picture is compressed. At first I though this was a geometry issue but after futher experimentation, I found that I could get an even picture by changing the mode to 80 columns using the dos "mode 80" command. When I run it in this mode the screen geometry is good but it doesn't take up the full area of the screen. I even managed to get Windows 2.0 running in monochrome mode and it looks ok, but same issue with taking up a reduced area of the screen. See pics below.

I suspect it's related to the monochrome mode being output by my display adapter, a Video7 VEGA (VGA/EGA).

It's a little hard to see in the photo, but if you look at the very right of the picture you'll see that the picture is squashed:

Here it is in 80 column mode, geometry is ok but there's a wide border around the graphic area:

 

[modem7]

Early monitors had large borders.
For comparison purposes, the borders on my 5151 are: left = 1", right = 1/2", top = 1/2", bottom = 1/2"
Looks like mine needs to be shifted to the left a little.

I suspect it's related to the monochrome mode being output by my display adapter, a Video7 VEGA (VGA/EGA).

My VEGA VGA card is probably the same (we got it from the same place). I'll see if my card driving a 5151 does the same. What switch settings are you using?

 

[kingchops]

M7,

Before I do the mode change, borders on mine are: left, top, bottom = 1/2", right = 1.5"

But when I do the mode change, they are: top = 3/4", left, right, bottom = just over 1/2"

Switch settings that I've found to work are:

- All down (auto mode)

Or

1,2,3 & 6 up, 4 & 5 down (mono mode)

I also tried 1,2,3 up and 4,5,6 down. That seemed to work too.

I found a great reference for the switch settings on the Video7 VEGA VGA, problem was it was in Sweedish. But I translated it using Google translate. Great thing is he's got examples of what switches to use for different monitors. See here:

************************


SW1:1-3 Monitortyp. SW1:1 1:2 1:3
Automatisk avkänning, autoswitching (defualt) OFF OFF OFF
NEC Multisync, Nanao8060/9070, Princeton Ultrasync ON OFF OFF
Sony Multiscan, Mitsubishi, Taxan, Thomson OFF ON OFF
NEC Multisync Plus, NEC Multisync XL ON ON OFF
IBM PS/2 Analog display, or equivalent OFF OFF ON
IBM Color display (CGA), or equivalent ON OFF ON
IBM Enhanced color display (EGA), or equivalent OFF ON ON
IBM Monocrome display (MDA,Hercules), or equivalent ON ON ON

SW1:4 Primary / Secondary. OFF = Primary (default), ON = Secondary. Two monitors
can only be used if one is CGA and the other MDA (Hercules32kB).
VEGA is set as Secondary as it adapts to existing cards, ie
is there one CGA becomes VEGA one MDA and vice versa.

SW1:5 Auto Switching. ON = Autoswitshing On (default), OFF = Pure VGA Mode.
OFF is required for those times (= OS / 2) when VEGA just be (and must) behave
as a standard IBM VGA card.

SW1:6 Initial boot fashion. OFF = start in VGA mode, ON = starts in CGA/Hercules-
mode (depending on SW1 :1-3). Default = OFF.

 

[modem7]

I put my VEGA VGA card in one of my 5150s and had it drive a 5151 monitor.
VEGA VGA switches were set 1/2/3/6 DOWN and 4/5 UP.
At power on, on the screen was displayed "VEGA VGA BIOS Version 1.47" (followed by a Copyright line).

At the DOS prompt, I typed in as many X characters so as to get the Xs as far right as possible. At a point (80 character width), the Xs then wrapped to the next line. But the X on the far right was not distorted/compressed.

I then used the internal horizontal width adjustment (an adjustable coil) to widen the raster. I got the raster going all the way to the bezel. There was no distortion. The characters were slightly wider than normal, but no distortion.
WARNING: Due to plastic aging, the plastic part of my coil started breaking as I was adjusting it.

There are no other horizontal related adjustments.

I decided to run the video tests in Checkit. Checkit was unaware of the situation (VGA card driving mono monitor), because it appeared to run every video mode, which of course included ones that caused problems for the 5151. So that tells me that it's possible that other software that changes video modes may also not appreciate the situation.

You say that all is good after you run MODE 80. Is it possible that you have something in your CONFIG.SYS/AUTOEXEC.BAT that is triggering the problem.

1,2,3 & 6 up, 4 & 5 down (mono mode)

I would describe that as 1/2/3/6 DOWN and 4/5 UP (because DOWN on my card is ON)

 

[kingchops]

That's interesting I don't get any bios info with my VEGA card. Ok, sounds like you get better results than me on initial start-up. I've noticed with my monitor that it takes about 1 minute to warm up before it will display anything, so that's obviously not right, but once warmed up it seems to display ok. It still comes up with the right hand side squashed. Just to clarify the switch positions, I was talking in reverse, switch away from the number was up, but it actually works as you've got it in the picture. See below how I had mine set.

I've taken a couple of clearer pictures to show you how the right hand side displays before I do the mode 80. I've checked autoexec.bat and config.sys nothing special in there that could be causing it. What I will do is try my CGA card and see what results I get from that, would be interesting to compare. I also pulled the monitor apart yesterday, I gave it a good clean and also checked out the yoke adjustments and the vertical and horizontal adjustments. I didn't change anything. I looked at all the pots and it seems they have never been adjusted as the glue is still in tact on all of them including the yoke.

Here's a pic which shows you the right side of the screen at start-up, as you can see you can't read the word "Help" and the scroll bar looks like a thin line:

And here's what it looks like after I run "mode 80". The word "Help" looks much better as does the scroll bar:

Switch settings I used, although your combination worked the same on mine as well:

 

[modem7]

I've noticed with my monitor that it takes about 1 minute to warm up before it will display anything, so that's obviously not right, but once warmed up it seems to display ok.

From cold (off for at least 30 minutes), mine takes about 15 seconds before I start seeing the blinking 5150 cursor slowly start to make an appearance.

That's interesting I don't get any bios info with my VEGA card.

And mine shows no video whatsoever on the 5151 when 1/2/3/4/5 = DOWN and 6 = UP is selected.
It sounds like we have slightly different cards, with the possibility being that the difference may only be in the revision of BIOS.
Another possibility is that there is a configuration program for the card that allows extra configuration (e.g. BIOS start-up banner off/on).

I've taken a couple of clearer pictures to show you how the right hand side displays before I do the mode 80. I've checked autoexec.bat and config.sys nothing special in there that could be causing it.

The fact that all is good after the MODE 80 command suggests to me that:
1. Your 5151 isn't the problem; and
2. At card start, it is outputting non-standard monochrome sync signals; and
3. The MODE 80 results in the card outputting standard monochrome sync signals.

If you have an oscilloscope, you'll be able to check that hypothesis (comparing the sync waveforms to those [here]).

What I will do is try my CGA card and see what results I get from that

Clearly not an IBM CGA card.