[comp.sys.atari.st] SM124 mono monitor adjust query

jfbruno@rodan.acs.syr.edu (John F. Bruno) (02/20/90)

  My monochrome SM124 monitor has a problem where the right side of
the screen is shorter than the left side, so the screen isn't a 
perfect rectangle.  Has anyone else had this problem? Is it even
fixable?  There aren't any Atari Service Centers nearby (of course)
and I don't really feel like forking over a flat rate service charge
for something that (I hope) is a simple adjustment to make...

I'd appreciate any help w/this

---jb (jfbruno@rodan.acs.syr.edu)

bwhite@oucsace.cs.OHIOU.EDU (Bill White) (02/25/90)

In article <2137@rodan.acs.syr.edu>, jfbruno@rodan.acs.syr.edu (John F. Bruno) writes:
> 
>   My monochrome SM124 monitor has a problem where the right side of
> the screen is shorter than the left side, so the screen isn't a 
> perfect rectangle.  Has anyone else had this problem? Is it even
> fixable?  There aren't any Atari Service Centers nearby (of course)
> and I don't really feel like forking over a flat rate service charge
> for something that (I hope) is a simple adjustment to make...
> 
> I'd appreciate any help w/this
> 
> ---jb (jfbruno@rodan.acs.syr.edu)

	My guess is that it's probably either 1) magnetic fields, or 2)
assymetry in the yoke compensation magnets.
	If it's the first problem, check and make sure nothing is sitting
near your monitor that could be making magnetic fields.  If you move a
peripheral and your distortion goes away, that's it.  If not, try degaussing
your monitor screen.
	You can do this yourself if you have a degaussing coil (which you
can get at a TV repair shop) or you can bring the monitor to a TV repair
shop and have it done for you.  To use a degaussing coil, first take your
monitor AWAY FROM ANY MAGNETIC-SENSITIVE MEDIA (floppies, hard drive, etc)
and place it on a large flat surface, sitting normally.  Try and make the
video cable connect to it (you can move the computer too, it isn't magnetic
sensitive as long as there's no floppy disk in it).  Just keep the computer
as far away as the monitor cable will allow.
	Boot up and get something on the screen, and then plug in the
degaussing coil, at least 6' away from the monitor.  Using a reciprocating
motion, move the coil around and slowly bring it towards the front of the
monitor.  You should be making a big enough circle so that your hands go
in a path about 4' or so in diameter.  bring it up to the point where the
screen is very distorted, about 4" distance or so (depending on your
degaussing coil this may be more or less), and slowly bring it backwards,
keeping the same reciprocating motion until you're at least 6' away again.
	Repeat the procedure on the top and sides of the monitor.  DO NOT
PERFORM THIS OPERATION ON THE BACK OF THE MONITOR!  To do so would be
extremely dangerous to both you and the monitor.

	If this doesn't help, then your problem is in the CRT's yoke
compensator magnets, most likely.  Unless you have experience in aligning
these, I'd suggest you take your monitor to a computer repair shop, give
them the specifics of horizontal and vertical scan frequencies, and let
them do it.  It can be a very difficult procedure.
	If your monitor doesn't have adjustable compensator magnets, you're
out of luck.  If you really want a rectangular screen, you'll have to get
a new CRT (probably $200 or so).

					Bill White
					bwhite@oucsace.cs.ohiou.edu

mccann@rbdc (Mike McCann) (03/05/90)

s is stupid (pardon my honesty), I work on monitors for a living, and there is ABSOLUTELY NOTHING a degaussing coil can do to help a monochrome monitor! If the man has a color monitor or tv nearby, or external speakers, they should be moved first; if that ain't it THEN we mess with the things magnets. But don't degauss, you will probably only erase your disks!

EOF