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(Nearly) no screen output on 5150/5151

AJM71

New Member
Joined
Oct 25, 2018
Messages
5
Location
Germany
Hi,

I have a problem with my 5150:
Because the top and bottom borders on the 5151 monitor where quite big I decided to adjust them with the internal "Vertical Size" potentiometer. This worked really well and I didn't change anything else. (For "Horizontal Size" there doesn't seem to be a similar control.)
I "tested" it with about 15 minutes of Tetris and then somethings happened, but I can't remember if the picture froze or went just dark.
Anyhow - when I now restart the computer (without my "XT CF LITE 4.1" harddisk emulator installed) it beeps once - as usual - and seems boot properly from disk and when I later enter "dir a:" or "dir b:" the drives react as they should, BUT I don't see anything on the screen - no cursor - nothing.
So it would seem that the monitor or graphic card has a general problem.

But now comes the strange part!: If the "XT CF LITE" is installed, it seems to boot from that as well without problem, but at that moment there comes an output on the screen - sharp and clear in the first line:

Code:
[FONT=Courier New][B]A>>        C>>        F6       F8[/B][/FONT]

Nothing before that and nothing after that and after about 10 seconds this line disappears as well. That baffles me to a certain extent.

My plan now is to get a second graphic card and compare the behaviour. Does maybe anybody have another idea?
 
As a second phase of testing, remove the XT CF LITE card and let it boot into BASIC. There is both a line on top and a line on bottom when BASIC starts, which you can use for additional verification or adjustment.
 
Thank you for your response. Booting into cassette basic didn't bring any output, but I did some further testing and it seems the deciding factor is not the position of the output, but the intensity:
When I managed to start (blindly) the two games "beast" and "nyet" it became obvious, that all bright/bold characters are displayed, but the normal ones are not.
I'm just not sure if that points more to a fault of the monitor or the MDA adapter.
 
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