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Old 02-14-2013, 04:06 PM
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lnx64 lnx64 is offline
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Raster Rotation

Not exactly a TV, but close enough. The raster on my old IBM computers monochrome CRT, is slightly rotated.

Do I just simply rotate the yoke to fix this?

http://img.photobucket.com/albums/v3...ps9b310c6e.jpg

Also, if you look at the line at the bottom of the screen, it's not straight either, kind of like it bows slightly.
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Old 02-14-2013, 04:44 PM
walterbeers walterbeers is offline
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Yes, rotating the yoke will rotate the image, however it won't do anything for the bowing. Maybe there is some kind of pincushing controls, but on one that old I doubt it. Tilted picture was also a very common problem with TVs as well. I don't know why, but somehow they seemed to rotate themselves, probablly from the heat inside the monitor or set.
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Old 02-14-2013, 10:31 PM
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lnx64 lnx64 is offline
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Crap, the yoke is GLUED in place.

I don't think I'm going to be able to fix this rotation without breaking the tube.
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Old 02-14-2013, 10:59 PM
Geoff Bourquin Geoff Bourquin is offline
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Some monitors have a rotate option in the menu. Also, there could be something nearby that is magnatized causing the rotation. Maybe a pot someplace.
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Old 02-15-2013, 08:44 AM
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lnx64 lnx64 is offline
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This monitor is built into the computer, and it's from the 80's, it has no menu. The monitor is a dumb fixed frequency monitor that only knows 31KHz 60Hz 480 line (or 70Hz 400 line).

I thought it was magnetism but I've tried all sorts of locations in the house, same slight rotation.
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Old 02-15-2013, 09:36 AM
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crtfool crtfool is offline
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Are you sure that this is a new problem? Maybe you just never really noticed it before. It is unlikely that a monitor this old with a cemented yoke could just shift the raster rotation. The slight pincushioning may be adjustable, but I would not attempt it.

I am a bit of a fanatic when it comes to geometry issues, but your monitor looks great to me - the crosshatch is nearly perfect, as far as I am concerned - this would not bother me at all.
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Old 02-15-2013, 10:37 AM
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...

Last edited by andy; 12-05-2021 at 08:04 PM.
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Old 02-15-2013, 11:42 AM
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lnx64 lnx64 is offline
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It's definitely glued. I loosened the clamps and it won't budge. It looks like hot glue was placed all around the yoke.. I could probably try and scrape it off but I'd likely damage the CRT.

I don't know if this is a new thing or not. I only noticed it now to be honest.

I have an old picture of me from when I was a little kid, standing in front of this computer when it was in DOS Shell (all white background). I'll need to see if it looked rotated then too.
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  #9  
Old 02-15-2013, 10:37 PM
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old_tv_nut old_tv_nut is offline
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Looks to me like it's original. You could look to see if there are permanent magnets for geometry correction - if not, it is what it is.
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Old 02-15-2013, 11:04 PM
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Ok, I'll check for magnets, didn't see anything though. If anything I'll just leave it. rotation is my biggest pet peeve.
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Old 02-16-2013, 12:04 PM
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holmesuser01 holmesuser01 is offline
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I've seen worse on monitors that people are using today.

I'd leave that one alone, too.
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Old 02-16-2013, 03:34 PM
Geoff Bourquin Geoff Bourquin is offline
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What about rotating the whole CRT? Maybe the screws (or bolts) on the corner ears are a tad loose and allowed the whole tube to move.
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Old 02-16-2013, 03:56 PM
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Eric H Eric H is offline
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Fixed it in Photoshop for you, seems to be about .2 degrees off.

Tilt bugs me too, the yoke should be able to rotate, how about a shot of the yoke so we can see what's holding it. Hot Glue is pretty easy to remove, if it Epoxy then not so much. Geometry on a CRT is never going to be perfect, even with pincushion controls they are usually a bit bent.

Maybe if you sat a Magnet on the top left corner it would pull the beam up?
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File Type: jpg rotated.jpg (38.3 KB, 8 views)
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  #14  
Old 02-16-2013, 04:15 PM
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I don't personally have an internal pic since I had buttoned the computer back up, but one of my friends has the same model and an internal pic from his, and his yoke is glued the say way.

http://kishy.dyndns.org/?attachment_id=419
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  #15  
Old 02-16-2013, 04:36 PM
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old_tv_nut old_tv_nut is offline
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What are these?
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File Type: jpg what are these.jpg (49.8 KB, 16 views)
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