From: rseymour@reed.edu (Robert Seymour)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Sony 1304 monitor affected by speakers?
Keywords: sony, monitors, trinitron, apeture grill
Date: 13 Nov 92 00:41:46 GMT
Article-I.D.: reed.1992Nov13.004146.24537
Reply-To: rseymour@reed.edu
Organization: Reed College, Portland, OR

In article <275@opel.secondsource.COM> johnk@opel.secondsource.COM (John  
Kennedy) writes:
> In article <wright.55.0@lims01.lerc.nasa.gov> wright@lims01.lerc.nasa.gov  
(Ted Wright) writes:
> -In article <Bwr6CK.L0G@da_vinci.it.uswc.uswest.com>  
plyall@lookout.it.uswc.uswest.com (Pete Lyall) writes:
> ->From: plyall@lookout.it.uswc.uswest.com (Pete Lyall)
> ->Subject: Sony 1304 monitor affected by speakers?
> ->I use a Sony 1304 monitor, and when I had a light background up, I
> ->noted that there appeared to be a large dirty horizontal band...
> -
> -If you mean the faint horizontal stripe about 2/3 of the way down the
> -screen, I believe that all Trinitron picture tubes in computer monitors
> -have this. We have about 20 Sieko monitors with trinitron tubes that
> -do this. Every Sony monitor I have seen does this. This does not appear to
> -be fixable.
> 
> Actually, there are two such bands, about 1 pixel high each.  These are not
> "fixable", because they are part of the design.  Because the Trinitron tube  
is
> cylindrical in shape, rather than a spherical section,  the screen is divided
> into three areas.  These two lines are the borders between those areas.
> 
> -- 
> John Kennedy                     uunet!opel!johnk
> Second Source, Inc.              johnk@secondsource.COM 
> Annapolis, MD

	Actually, that's not quite right (or this is what it sounds like to me  
at least...). The trinitron tube is indeed cylindrical (though not divided),  
but what causes the above problem is the design of the shadowcast. In all color  
monitors, the regions of different colors are divided by a dark contrast space. 
	In convential shadow-mask (i.e. tridot) this is caused by the fact that  
the glass has a dark coarting except where the phosphor dots are placed. The  
three electron guns then fire excited electrons at the dots, which emit light  
at the proper frequency and luminance.
	However, in a trinitron tube (patented by Sony Electronics), the  
scenario is wholly different. A trinitron monitor has one large electron gun  
which fires through a series of thin wires called an aperture grill(e). The  
three electron beams are shot through a coaxial magnetic field, shine throuhg  
the grill, and strike the glass. 
	The apeture grill is made of many thin wires running parallel in a  
vertical orientation. Each space in between two wires is a single color the  
height of the scan height (i.e. # of scan lines / vertical area covered). These  
colors are staggered after each scan to reduce banding.
	When the apeture grill become large (it must be a good distance away  
from the gun, then vibrations or stress can cause the grill to move (each wire  
is held under tension at only the top and bottom. To prevent wavering of the  
image, a horixontal wire is run along the apeture grill so that vibrations will  
be countered by the additional structural integrity of the stabilizing wire.  
	This horizontal wire is what you see on your scree. Since it runs  
parallel to the scan, it is sometimes noticable as a shadow across a bright  
background. On a CPD-1304 or CPD-1320 (multisynchronous version), there is one  
such stabilizing wires. Larger tubes often have two or in rare cases three  
stabilizing wires.

--
Robert Seymour				rseymour@reed.edu
Departments of Physics and Philosophy
Artificial Life Project			Reed College
Reed Solar Energy Project (SolTrain)	Portland, OR