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fsmith2003
October 19th, 2017, 01:53 PM
My IBM 5151 monitor which is attached to my 5150 is not working correctly. It does not show anything on the screen and when the brightness is turned all the way up it's just all green with diagonal lines across the screen. Are there any solutions to this that any of you are aware of?

And yes the computer does work. Hooked up to a Tandy monitor it comes up fine.

vwestlife
October 19th, 2017, 04:25 PM
You do have it connected to an MDA/Hercules video card, or EGA in monochrome mode, right? It won't work if you try to connect it to a CGA card or an EGA card in color mode.

fsmith2003
October 19th, 2017, 04:30 PM
You do have it connected to an MDA/Hercules video card, or EGA in monochrome mode, right? It won't work if you try to connect it to a CGA card or an EGA card in color mode.

Correct... this exact setup has worked before. Just turned on today and noticed this.

KC9UDX
October 19th, 2017, 04:50 PM
Could the cable have been mechanically stressed recently? Even if not, I'd ring out the cable.

If it's not the cable, it's possibly the video amplifier.

fsmith2003
October 20th, 2017, 07:48 AM
Is there a way to check the amplifier by chance?

KC9UDX
October 20th, 2017, 08:40 AM
Is there a way to check the amplifier by chance?
Sure, but you'll need an oscilloscope, some knowledge on using one, and probably a schematic of monitor.

fsmith2003
October 20th, 2017, 12:24 PM
41407

Just so you all can see what I am getting on the screen.

Trixter
October 20th, 2017, 07:53 PM
That's usually what I see on monochrome screens that have the brightness turned all the way up. Have you tried recapping?

evildragon
October 20th, 2017, 09:18 PM
41407

Just so you all can see what I am getting on the screen.

Looks like you have a raster, but no video signal. The lines are simply retrace lines from having brightness set so high..

I'd honestly check into the cable itself having an open circuit from the signal itself.

fsmith2003
October 21st, 2017, 12:49 PM
Checked the cable but still a no go. I know its getting something from the computer because when you unplug the video cable the screen goes off.

retrogear
October 21st, 2017, 02:30 PM
The service manual is online. I'm looking at it now. Do you have a voltmeter and know how to use one? You would have to open the display up and slide the main board out to get to TR18 labeled dead center of the board.
Measure voltages on leads B C and E. E is ground so 0V. B should be -1.6V and C = 4.3V. If video signal is not getting to TR18 then B will not be a negative reading. I can walk you thru more checks after that. There is no
quick solution here. There are very few caps involved with the video path so doubt it's one of those.

Larry G

fsmith2003
October 24th, 2017, 06:09 AM
The service manual is online. I'm looking at it now. Do you have a voltmeter and know how to use one? You would have to open the display up and slide the main board out to get to TR18 labeled dead center of the board.
Measure voltages on leads B C and E. E is ground so 0V. B should be -1.6V and C = 4.3V. If video signal is not getting to TR18 then B will not be a negative reading. I can walk you thru more checks after that. There is no
quick solution here. There are very few caps involved with the video path so doubt it's one of those.

Larry G

That may be all above my skill level lol. If I get time to try and tackle that I will let you know and maybe I can learn a few things.