CurtPalme.com Home Theater Forum

lyd · Joined: 15 Sep 2007 Posts: 390 Location: Lake Mills, Wi

Is this a known thing? It is not visible except in very light scenes, but it is definitely noticeable when it appears. There is a sort of line of noise dead on the horizontal center, and the top half is just a tiny bit darker than the bottom half.

I've been noticing that there is quite a lot of noise in general in lighter stuff, so I don't know if that is related. I also know that there are numerous upgrades and fixes I can do to reduce the noise, but I guess I was kind of hoping there would be a simpler answer to the half-and-half thing. Is there?

I think I would really prefer to just buy some Mike Parker-modded boards rather than start replacing things myself on these, but if comes to it I at least want to obtain a set of spares to work with first. Not sure the best way to go about that...

lyd

Bruce 09 · Posted: Sat Mar 15, 2008 12:41 am Post subject:

http://www.etechvideo.com/techtip10.htm

Bruce

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Sounds like you mean banding, where its almost like a two tone thing going on. one part of the images is sligtly darker than the other, ands it goes perfectly across the whole screen. That is called banding. its caused by using too much of any or a combination of convergance,bow,and the linerity controls. Its a pain to get rid of if you do not have the projector set up mechanicly correct. The raster should be centerd, the image centerd in the raster, the horizone should be level and the the astig should be close although not as important for banding as the rest. You will first nedd to reset your convergence to zero, or start completely over wiht a total restet fo the Projector. get it centerd to the screen as perfectly as you can after you center the raster . it's easier to center the ratser by using the edges of the raster then using cross hatch center to center. I put up the whit feild and center it corner to corner. Then I physicly move the projector to get the white field completly on the screen centered. Also i forgot to mention use the external source for this. I use my Lumagens white field . This will allow you to use less of phase for centering the picture. then Go into gonvegance and do a convergence with out doing any of the other settings yet, i straighten it out after. Once its all converged use the size and any phaze to get the grid to fill the screen. the use the other controls to get the geometry right and try not to use any bow, that is what causes banding the most. then go through and do the convergance again. use interpolated as this introduces the les banding.

Athanasios

lyd · Joined: 15 Sep 2007 Posts: 390 Location: Lake Mills, Wi

Oh. Hmm. This doesn't look like the sort of "banding" I have experienced in other contexts, and didn't seem much like what was described in that tech tip and elsewhere, so I thought it was something else.

I don't think I'm using any bow at all, but I do have a pretty fair amount of top and bottom pin and always use point (random access) convergence for all colors. I'll try zeroing all the pin and resetting convergence and see if it goes away, then follow the suggestions in that tip to set up again if it does.

Thanks.

lyd

lyd · Joined: 15 Sep 2007 Posts: 390 Location: Lake Mills, Wi

Well, the good news is that this was definitely the problem. With convergence reset and all the pin and keystone zeroed the banding goes away.

The bad news is that I am currently too far off, when I sync to my source, to get things straightened out using interpolated green convergence without re-introducing it, and badly.

Guess there is yet another re-jiggering of the physical setup in my future. This didn't happen before I "fixed" it in the last round.

Might be time to try Elaine's all-visual approach. Measuring has not been good to me.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

The best way is to put a source to your projector and put up an all whit test pattern from the source. Center that pattern on the face of the green tube. then project the image to the screen and physically center that image to the screen. but this must be done after a complete magnetics set up, you have to get the astig and focus magnets centerd for the internal grid patterns then you move onto the external image centering. Once you have all the set banding shoul;d go away.

Athanasios