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Discussion Starter · #1 ·
Can someone help me out, first of all I'm a newbie - but I'm not afraid. On my recently acquired NEC XG1100 I have squiggles shaped like the top half of an "S" on the very top of all the cross-hair test patterns (only these test patterns). It doesn't affect my image, and it is only present in the cross-hair pattens. Each vertical line of the cross patterns ends with a squiggle on top. Interestingly enough, when I disconncected my RGB H/V cable from the NEC IDC 3000 image processor/line doubler and put the test pattern up with out a signal - the squiggles disappeared and the pattern is fine. In addtion to the squiggles it seems as though the first 5% of the top of the screen has been squished down (much more evident in the finer cross patterns). Is it my doubler signal, my cable (do I need to use a 5 cable connection rather than 4?), is there a problem with the projector? I've noticed a few other posts in the past about it similar problem, but nobody can back to identify exactly what the problem was and how to solve it. Can someone help?
 

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Blargh. I had the same problem in the upper left of my Bacro 808 about a year ago. We had a thread about it, and I think we resolved it, at least on the 808 machine. A few others have had the same problem around the same time, and I can't remember right now what fixed it.


Have you tried adjusting the h phase a little? I think it has to do with the projector not locking onto the video signal properly, which is why it fixes itself when you disconnect the cable.


Oh, I remember now. If this is the upper left corner of the screen, the problem is the raster is unstable in this corner as the gun is recovering from the vertical retrace it must do between frames. If your image area is too close to this unstable region, or is inside of it, you see the effect on screen.


To fix it, you can try to use the h phase control (and v phase if available) to shift the image a tad within the raster. Also, adjusting the timing in your source may help. I only use an HTPC, so I was able to tweak my PowerStrip timing settings to have a longer front / left porch with my video frame to ensure that the gun had time to recover before drawing the image.
 

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Discussion Starter · #3 ·
Spearce, Thanks for the reply. The compression of the image on the top of the pattern is fairly consistent across the entire top of the screen (rather than just one corner). I'll take a look at the image/raster position within the tube. I'm trying to do my initial fresh setup and was fairly confident I had the rasters centered with a minimum of 1/2" from the edge of the tubes. Perhaps adjusting the H/V in the Phase control will help.
 

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Yea, the raster might be centered, but the source controls the position of the image within the raster. You may not have enough porch on the top edge (I think that's the front porch).


If the top is squeezed down, you might need to retweak your vertical linearity control. That might need to be done after you do the v phase.


NECs are (supposedly) sensitive to the order you apply geometry controls. I know my Barco is, if I go through in a circle the controls start to affect each other and its hard to correct the image, or a "defect" builds up. Some projectors build a horizontal line dead center on the screen as a result of "bad ordering" on geometry controls. Nobody is sure why, and its one of the black arts of CRT setup. This may resolve itself on your next setup (from scratch) as you do it in a little different order. :)
 
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