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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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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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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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It doesn't look that bad to me, but are you sure the yoke is really glued on? I've never seen a permanently bonded yoke on a monochrome monitor. There may be some silicone, or other glue to hold it in position, but you can probably remove it.

Pincushion correction is usually adjusted by rotating small magnets around the perimeter of the yoke. They're probably glued in place, but the glue can be cut off and replaced with silicone after adjustment.
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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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Old 02-15-2013, 10:37 PM
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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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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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What are these?
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File Type: jpg what are these.jpg (49.8 KB, 15 views)
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