Is anyone here familiar with qbasic programs and specifically programs using com ports? I'm trying to run the attached program in dosbox but whenever it gets to the OPEN COM1 line it fails with a device timeout error. I get the same error even on a physical pc running dos, and the serial port is set …

Hello again, as an update I would like to inform you that I have solved the problem by replacing the integrated IC201, this is the SN7406 used as a video buffer (inverted). I hope this tip will be helpful. The diagnosis was made by analyzing the output pin (8) on which there was no signal (the …

I have a CGA monitor that I got from the US (it is 60Hz) and I'm trying to use it in the UK, with 50Hz mains. When I try to use it with either of the 2 CGA cards I have, the video constantly moves across the screen. Is this an issue with the mains frequency or can I adjust something inside the …

The contrast knob feels like it is turning the potentiometer behind it, and it turns smoothly, but I can't see any changes on the screen when I turn it. I only have the one MDA card and my computer refuses to boot when I set up this card to start as a MDA card, is there any other way to get …

Here is a video I took of turning the brightness from 0 to max, there should be a C prompt with some text at the top. I have also tried turning the brightness so I can just about see the retrace lines, and I have left the monitor like that for 10 minutes, but after that still only the retrace lines …

The retrace lines appear before anything else on the screen, when I turn the brightness up from 0 the lines are the first thing I see, no matter what the contrast is set to. I can start to see the lines from about 5 seconds after the monitor turns on. Could this be a problem with the MDA card …

Hi everyone This is my first post here so I hope I am doing everything right. I have just bought an IBM 5151, and MDA card on ebay, 'spares or repair'. Obviously when I received it, the monitor isn't working properly. There are horizontal lines going across the screen whenever it's turned on and the …