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What does "convergence issues" and "geometry issues" mean?

1062 Views 7 Replies 6 Participants Last post by  Dark Rain
Even though I have been on the forum for close to a year, I need to have this question answered for me.


I need the answer dumb down to fully understand what each means.


In other words what am I looking for to see if i have "convergence problems"?


Same thing for "geometry issues". What am I looking for to see if I even have an issue with the geometry?


Also, do the 16:9 tube sets tend to "SUFFER" more from these issues than a $;3 tube set?
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First I don't think 16:9 vs. 4:3 makes much of a difference, all CRTs suffer from geometry and convergance issues to varying degrees. The bigger the size usually the more problems with both.


Geometry is pretty simple if you have a problem you won't be producing straight lines, square boxes and round circles. The best way to test for this is using a DVD with test patterns like Avia or DVE. You put up a test grid patter and check to see if all the lines are straight and boxes square etc. Same thing with circle patterns.


Convergence issues usually present themselves when the CRT is asked to make white lines on a black background (again use some test patterns to test for this). What you will see is faint blue or red either on the top or bottom or left or right hand side of the white lines. This is usually most noticeable in the far edges and corners on bigger CRTs. The electron gun isn't aimed exactly where it is supposed to hit and it excites some blue or red pixels at the edge of the line.
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Geometry problems are noticeable if you put up a test pattern with crosshatched lines and circles. Distortions will cause circles to not appear round and lines to be tilted or curved instead of straight and possibly lines noting being parallel. Convergence problems causes the 3 colors per pixel (red,green,blue) to not align so you get blue or red areas if its off.
A good example of a convergence problem is a poorly printed color picture in a news paper - if you've seen one you'll know exactly what I'm talking about. same thing happens with CRTs...
Quote:
Originally posted by ccallana
A good example of a convergence problem is a poorly printed color picture in a news paper - if you've seen one you'll know exactly what I'm talking about. same thing happens with CRTs...
I think what you are referring to is something else called the moire effect. You can do a google search on this and get some much better explanation than I can give you.


Hey Steelersrule - Weren't you on another thread saying that you laugh at people who look too closely for things that are wrong with their TVs? :)
Quote:
Originally posted by jackbnimble


Hey Steelersrule - Weren't you on another thread saying that you laugh at people who look too closely for things that are wrong with their TVs? :)
Yes, that was me.


Somewhere along the line I forgot what the hell these terms meant, and what it was when you had that sort of problem.


All these damn terms are starting to get mish-mashed in my brain. But thanks to everyone, especially Dearth for a "dumb down" definition, of what the two meant.


I like to reiterate that I have learned a TON on these forums, GREATLY IMPROVED my TV picture, and have bought things for my HT based on recommendations from people on these forums based on my specific needs and wants(which change over time just like everyone else).


But sometimes all the ******#$ from posters about their TV'S picture get's too me.


Especially when you read about what extremes people go through to reach the conclusion that something is wrong with their tv.


EXAMPLE: While watching my tv the other night I noticed if you look at the tv at a 67 degree angle, with one leg in the air, while licking the screen, with a full moon, with the stockmarket on the rise, the lights in the room flicked on and off, you can see the image of dancing gremlins in the upper right corner of the screen, about an 1/8 of an inch long/high, all laughing at me that I am a moron for doing this.


I need to GET RID OF THIS TV. NOBODY BUY THIS MODEL!!! IT IS DEFECTIVE!!!!


Now, of course, I am poking fun at these people that do this, but read the posts by some who feel their tv is bad. Look at how far they take it to show something is wrong.


These posters remind me of a friend of mine's father, who after the 1996 World Series won by the Yankees, right after the final out was made(Remember, the Yanks had not won one in about 20 years. I am a Pittsburgh Pirate fan. Yes there is still a team in Pitssburgh, and thank you for your sympathy) said too his son, my friend, "Well, they WON'T WIN IT NEXT YEAR."(which they didn't, of course, the Marlins did).


But who could not even enjoy the moment.


I feel that some people feel this way about their tv's, HT set-ups.


Sad.
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Those gremlins were laughing WITH me, not AT me.
When you pay $1000-$2500 for a CRT TV, you shouldn't have excessive geometry/convergence problems with it. There's a certain point where these two issues can be very distracting and you either try to get them fixed or send the TV back for an exchange or refund. Some people get lucky or are just "happy" with their first TV purchase, while others get a bad one or may just be very picky. For the money they spend, it's not for YOU to decide whether or not they're being too picky. It's their money and they have every right to complain if they're unhappy.


CRTs by default are not going to give a perfect picture. It's whatever you find what's acceptable is all that matters.
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