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IBM 5151 Monitor Issue

fsmith2003

Experienced Member
Joined
Nov 2, 2016
Messages
72
Location
Illinois
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

Veteran Member
Joined
May 2, 2008
Messages
5,206
Location
central NJ
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

Experienced Member
Joined
Nov 2, 2016
Messages
72
Location
Illinois
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

Space Commander
Joined
Jan 27, 2014
Messages
7,468
Location
Lutenblag
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

Experienced Member
Joined
Nov 2, 2016
Messages
72
Location
Illinois
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

Veteran Member
Joined
Jan 29, 2014
Messages
1,063
Location
Minnesota
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

Experienced Member
Joined
Nov 2, 2016
Messages
72
Location
Illinois
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.
 
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